Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

30 files changed, 7264 insertions, 0 deletions

diff --git a/third_party/rust/wasm-encoder/src/component.rs b/third_party/rust/wasm-encoder/src/component.rs
new file mode 100644
index 0000000000..5f92a91f77
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component.rs
@@ -0,0 +1,160 @@
+mod aliases;
+mod canonicals;
+mod components;
+mod exports;
+mod imports;
+mod instances;
+mod modules;
+mod names;
+mod start;
+mod types;
+
+pub use self::aliases::*;
+pub use self::canonicals::*;
+pub use self::components::*;
+pub use self::exports::*;
+pub use self::imports::*;
+pub use self::instances::*;
+pub use self::modules::*;
+pub use self::names::*;
+pub use self::start::*;
+pub use self::types::*;
+
+use crate::{CustomSection, Encode, ProducersSection};
+
+// Core sorts extended by the component model
+const CORE_TYPE_SORT: u8 = 0x10;
+const CORE_MODULE_SORT: u8 = 0x11;
+const CORE_INSTANCE_SORT: u8 = 0x12;
+
+const CORE_SORT: u8 = 0x00;
+const FUNCTION_SORT: u8 = 0x01;
+const VALUE_SORT: u8 = 0x02;
+const TYPE_SORT: u8 = 0x03;
+const COMPONENT_SORT: u8 = 0x04;
+const INSTANCE_SORT: u8 = 0x05;
+
+/// A WebAssembly component section.
+///
+/// Various builders defined in this crate already implement this trait, but you
+/// can also implement it yourself for your own custom section builders, or use
+/// `RawSection` to use a bunch of raw bytes as a section.
+pub trait ComponentSection: Encode {
+    /// Gets the section identifier for this section.
+    fn id(&self) -> u8;
+
+    /// Appends this section to the specified destination list of bytes.
+    fn append_to_component(&self, dst: &mut Vec<u8>) {
+        dst.push(self.id());
+        self.encode(dst);
+    }
+}
+
+/// Known section identifiers of WebAssembly components.
+///
+/// These sections are supported by the component model proposal.
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd)]
+#[repr(u8)]
+pub enum ComponentSectionId {
+    /// The section is a core custom section.
+    CoreCustom = 0,
+    /// The section is a core module section.
+    CoreModule = 1,
+    /// The section is a core instance section.
+    CoreInstance = 2,
+    /// The section is a core type section.
+    CoreType = 3,
+    /// The section is a component section.
+    Component = 4,
+    /// The section is an instance section.
+    Instance = 5,
+    /// The section is an alias section.
+    Alias = 6,
+    /// The section is a type section.
+    Type = 7,
+    /// The section is a canonical function section.
+    CanonicalFunction = 8,
+    /// The section is a start section.
+    Start = 9,
+    /// The section is an import section.
+    Import = 10,
+    /// The section is an export section.
+    Export = 11,
+}
+
+impl From<ComponentSectionId> for u8 {
+    #[inline]
+    fn from(id: ComponentSectionId) -> u8 {
+        id as u8
+    }
+}
+
+impl Encode for ComponentSectionId {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(*self as u8);
+    }
+}
+
+/// Represents a WebAssembly component that is being encoded.
+///
+/// Unlike core WebAssembly modules, the sections of a component
+/// may appear in any order and may be repeated.
+///
+/// Components may also added as a section to other components.
+#[derive(Clone, Debug)]
+pub struct Component {
+    bytes: Vec<u8>,
+}
+
+impl Component {
+    /// The 8-byte header at the beginning of all components.
+    #[rustfmt::skip]
+    pub const HEADER: [u8; 8] = [
+        // Magic
+        0x00, 0x61, 0x73, 0x6D,
+        // Version
+        0x0c, 0x00, 0x01, 0x00,
+    ];
+
+    /// Begin writing a new `Component`.
+    pub fn new() -> Self {
+        Self {
+            bytes: Self::HEADER.to_vec(),
+        }
+    }
+
+    /// Finish writing this component and extract ownership of the encoded bytes.
+    pub fn finish(self) -> Vec<u8> {
+        self.bytes
+    }
+
+    /// Write a section to this component.
+    pub fn section(&mut self, section: &impl ComponentSection) -> &mut Self {
+        self.bytes.push(section.id());
+        section.encode(&mut self.bytes);
+        self
+    }
+
+    /// View the encoded bytes.
+    pub fn as_slice(&self) -> &[u8] {
+        &self.bytes
+    }
+}
+
+impl Default for Component {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl ComponentSection for CustomSection<'_> {
+    fn id(&self) -> u8 {
+        ComponentSectionId::CoreCustom.into()
+    }
+}
+
+impl ComponentSection for ProducersSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::CoreCustom.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/aliases.rs b/third_party/rust/wasm-encoder/src/component/aliases.rs
new file mode 100644
index 0000000000..1e317fb0e2
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/aliases.rs
@@ -0,0 +1,160 @@
+use super::{COMPONENT_SORT, CORE_MODULE_SORT, CORE_SORT, CORE_TYPE_SORT, TYPE_SORT};
+use crate::{
+    encode_section, ComponentExportKind, ComponentSection, ComponentSectionId, Encode, ExportKind,
+};
+
+/// Represents the kinds of outer aliasable items in a component.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum ComponentOuterAliasKind {
+    /// The alias is to a core module.
+    CoreModule,
+    /// The alias is to a core type.
+    CoreType,
+    /// The alias is to a type.
+    Type,
+    /// The alias is to a component.
+    Component,
+}
+
+impl Encode for ComponentOuterAliasKind {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Self::CoreModule => {
+                sink.push(CORE_SORT);
+                sink.push(CORE_MODULE_SORT);
+            }
+            Self::CoreType => {
+                sink.push(CORE_SORT);
+                sink.push(CORE_TYPE_SORT);
+            }
+            Self::Type => sink.push(TYPE_SORT),
+            Self::Component => sink.push(COMPONENT_SORT),
+        }
+    }
+}
+
+/// An encoder for the alias section of WebAssembly component.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, Alias, ComponentAliasSection, ComponentExportKind, ComponentOuterAliasKind};
+///
+/// let mut aliases = ComponentAliasSection::new();
+/// aliases.alias(Alias::InstanceExport { instance: 0, kind: ComponentExportKind::Func, name: "f" });
+/// aliases.alias(Alias::Outer { count: 0, kind: ComponentOuterAliasKind::Type, index: 1 });
+///
+/// let mut component = Component::new();
+/// component.section(&aliases);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct ComponentAliasSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+/// Different forms of aliases that can be inserted into a
+/// [`ComponentAliasSection`].
+#[derive(Copy, Clone, Debug)]
+pub enum Alias<'a> {
+    /// An alias of a component instance export.
+    InstanceExport {
+        /// The index of the component instance that's being aliased from.
+        instance: u32,
+        /// The kind of item that's being extracted from the component
+        /// instance.
+        kind: ComponentExportKind,
+        /// The name of the export that's being aliased.
+        name: &'a str,
+    },
+    /// Same as `InstanceExport`, but for core instances.
+    #[allow(missing_docs)]
+    CoreInstanceExport {
+        instance: u32,
+        kind: ExportKind,
+        name: &'a str,
+    },
+    /// Aliasing an item from an outer component.
+    Outer {
+        /// The kind of item being aliased, either a type or a component.
+        kind: ComponentOuterAliasKind,
+        /// Number of levels "up" to go to lookup the index within. Level 0 is
+        /// the current scope and level 1 is the enclosing scope, and so on.
+        count: u32,
+        /// The index of the item to alias within the scope referenced by
+        /// `count`.
+        index: u32,
+    },
+}
+
+impl ComponentAliasSection {
+    /// Create a new alias section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of aliases in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an alias to a component instance's export.
+    pub fn alias(&mut self, alias: Alias<'_>) -> &mut Self {
+        alias.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for ComponentAliasSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for ComponentAliasSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::Alias.into()
+    }
+}
+
+impl Encode for Alias<'_> {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Alias::InstanceExport {
+                instance,
+                kind,
+                name,
+            } => {
+                kind.encode(sink);
+                sink.push(0x00);
+                instance.encode(sink);
+                name.encode(sink);
+            }
+            Alias::CoreInstanceExport {
+                instance,
+                kind,
+                name,
+            } => {
+                sink.push(CORE_SORT);
+                kind.encode(sink);
+                sink.push(0x01);
+                instance.encode(sink);
+                name.encode(sink);
+            }
+            Alias::Outer { kind, count, index } => {
+                kind.encode(sink);
+                sink.push(0x02);
+                count.encode(sink);
+                index.encode(sink);
+            }
+        }
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/canonicals.rs b/third_party/rust/wasm-encoder/src/component/canonicals.rs
new file mode 100644
index 0000000000..e81819c44e
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/canonicals.rs
@@ -0,0 +1,133 @@
+use crate::{encode_section, ComponentSection, ComponentSectionId, Encode};
+
+/// Represents options for canonical function definitions.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum CanonicalOption {
+    /// The string types in the function signature are UTF-8 encoded.
+    UTF8,
+    /// The string types in the function signature are UTF-16 encoded.
+    UTF16,
+    /// The string types in the function signature are compact UTF-16 encoded.
+    CompactUTF16,
+    /// The memory to use if the lifting or lowering of a function requires memory access.
+    ///
+    /// The value is an index to a core memory.
+    Memory(u32),
+    /// The realloc function to use if the lifting or lowering of a function requires memory
+    /// allocation.
+    ///
+    /// The value is an index to a core function of type `(func (param i32 i32 i32 i32) (result i32))`.
+    Realloc(u32),
+    /// The post-return function to use if the lifting of a function requires
+    /// cleanup after the function returns.
+    PostReturn(u32),
+}
+
+impl Encode for CanonicalOption {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Self::UTF8 => sink.push(0x00),
+            Self::UTF16 => sink.push(0x01),
+            Self::CompactUTF16 => sink.push(0x02),
+            Self::Memory(idx) => {
+                sink.push(0x03);
+                idx.encode(sink);
+            }
+            Self::Realloc(idx) => {
+                sink.push(0x04);
+                idx.encode(sink);
+            }
+            Self::PostReturn(idx) => {
+                sink.push(0x05);
+                idx.encode(sink);
+            }
+        }
+    }
+}
+
+/// An encoder for the canonical function section of WebAssembly components.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{Component, CanonicalFunctionSection, CanonicalOption};
+///
+/// let mut functions = CanonicalFunctionSection::new();
+/// functions.lift(0, 0, [CanonicalOption::UTF8]);
+///
+/// let mut component = Component::new();
+/// component.section(&functions);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct CanonicalFunctionSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl CanonicalFunctionSection {
+    /// Construct a new component function section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of functions in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define a function that will lift a core WebAssembly function to the canonical ABI.
+    pub fn lift<O>(&mut self, core_func_index: u32, type_index: u32, options: O) -> &mut Self
+    where
+        O: IntoIterator<Item = CanonicalOption>,
+        O::IntoIter: ExactSizeIterator,
+    {
+        let options = options.into_iter();
+        self.bytes.push(0x00);
+        self.bytes.push(0x00);
+        core_func_index.encode(&mut self.bytes);
+        options.len().encode(&mut self.bytes);
+        for option in options {
+            option.encode(&mut self.bytes);
+        }
+        type_index.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+
+    /// Define a function that will lower a canonical ABI function to a core WebAssembly function.
+    pub fn lower<O>(&mut self, func_index: u32, options: O) -> &mut Self
+    where
+        O: IntoIterator<Item = CanonicalOption>,
+        O::IntoIter: ExactSizeIterator,
+    {
+        let options = options.into_iter();
+        self.bytes.push(0x01);
+        self.bytes.push(0x00);
+        func_index.encode(&mut self.bytes);
+        options.len().encode(&mut self.bytes);
+        for option in options {
+            option.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for CanonicalFunctionSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for CanonicalFunctionSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::CanonicalFunction.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/components.rs b/third_party/rust/wasm-encoder/src/component/components.rs
new file mode 100644
index 0000000000..c08645e3b9
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/components.rs
@@ -0,0 +1,29 @@
+use crate::{Component, ComponentSection, ComponentSectionId, Encode};
+
+/// An encoder for the component section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, NestedComponentSection};
+///
+/// let mut nested = Component::new();
+/// let mut component = Component::new();
+/// component.section(&NestedComponentSection(&nested));
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug)]
+pub struct NestedComponentSection<'a>(pub &'a Component);
+
+impl Encode for NestedComponentSection<'_> {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.0.bytes.encode(sink);
+    }
+}
+
+impl ComponentSection for NestedComponentSection<'_> {
+    fn id(&self) -> u8 {
+        ComponentSectionId::Component.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/exports.rs b/third_party/rust/wasm-encoder/src/component/exports.rs
new file mode 100644
index 0000000000..9720d51b02
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/exports.rs
@@ -0,0 +1,125 @@
+use super::{
+    COMPONENT_SORT, CORE_MODULE_SORT, CORE_SORT, FUNCTION_SORT, INSTANCE_SORT, TYPE_SORT,
+    VALUE_SORT,
+};
+use crate::{encode_section, ComponentSection, ComponentSectionId, ComponentTypeRef, Encode};
+
+/// Represents the kind of an export from a WebAssembly component.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum ComponentExportKind {
+    /// The export is a core module.
+    Module,
+    /// The export is a function.
+    Func,
+    /// The export is a value.
+    Value,
+    /// The export is a type.
+    Type,
+    /// The export is an instance.
+    Instance,
+    /// The export is a component.
+    Component,
+}
+
+impl Encode for ComponentExportKind {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Self::Module => {
+                sink.push(CORE_SORT);
+                sink.push(CORE_MODULE_SORT);
+            }
+            Self::Func => {
+                sink.push(FUNCTION_SORT);
+            }
+            Self::Value => {
+                sink.push(VALUE_SORT);
+            }
+            Self::Type => {
+                sink.push(TYPE_SORT);
+            }
+            Self::Instance => {
+                sink.push(INSTANCE_SORT);
+            }
+            Self::Component => {
+                sink.push(COMPONENT_SORT);
+            }
+        }
+    }
+}
+
+/// An encoder for the export section of WebAssembly component.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, ComponentExportSection, ComponentExportKind};
+///
+/// // This exports a function named "foo"
+/// let mut exports = ComponentExportSection::new();
+/// exports.export("foo", "", ComponentExportKind::Func, 0, None);
+///
+/// let mut component = Component::new();
+/// component.section(&exports);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct ComponentExportSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl ComponentExportSection {
+    /// Create a new component export section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of exports in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an export in the export section.
+    pub fn export(
+        &mut self,
+        name: &str,
+        url: &str,
+        kind: ComponentExportKind,
+        index: u32,
+        ty: Option<ComponentTypeRef>,
+    ) -> &mut Self {
+        name.encode(&mut self.bytes);
+        url.encode(&mut self.bytes);
+        kind.encode(&mut self.bytes);
+        index.encode(&mut self.bytes);
+        match ty {
+            Some(ty) => {
+                self.bytes.push(0x01);
+                ty.encode(&mut self.bytes);
+            }
+            None => {
+                self.bytes.push(0x00);
+            }
+        }
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for ComponentExportSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for ComponentExportSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::Export.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/imports.rs b/third_party/rust/wasm-encoder/src/component/imports.rs
new file mode 100644
index 0000000000..8d843407f3
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/imports.rs
@@ -0,0 +1,151 @@
+use crate::{
+    encode_section, ComponentExportKind, ComponentSection, ComponentSectionId, ComponentValType,
+    Encode,
+};
+
+/// Represents the possible type bounds for type references.
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+pub enum TypeBounds {
+    /// The type is bounded by equality.
+    Eq,
+}
+
+impl Encode for TypeBounds {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Self::Eq => sink.push(0x00),
+        }
+    }
+}
+
+/// Represents a reference to a type.
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+pub enum ComponentTypeRef {
+    /// The reference is to a core module type.
+    ///
+    /// The index is expected to be core type index to a core module type.
+    Module(u32),
+    /// The reference is to a function type.
+    ///
+    /// The index is expected to be a type index to a function type.
+    Func(u32),
+    /// The reference is to a value type.
+    Value(ComponentValType),
+    /// The reference is to a bounded type.
+    ///
+    /// The index is expected to be a type index.
+    Type(TypeBounds, u32),
+    /// The reference is to an instance type.
+    ///
+    /// The index is expected to be a type index to an instance type.
+    Instance(u32),
+    /// The reference is to a component type.
+    ///
+    /// The index is expected to be a type index to a component type.
+    Component(u32),
+}
+
+impl ComponentTypeRef {
+    /// Gets the export kind of the reference.
+    pub fn kind(&self) -> ComponentExportKind {
+        match self {
+            Self::Module(_) => ComponentExportKind::Module,
+            Self::Func(_) => ComponentExportKind::Func,
+            Self::Value(_) => ComponentExportKind::Value,
+            Self::Type(..) => ComponentExportKind::Type,
+            Self::Instance(_) => ComponentExportKind::Instance,
+            Self::Component(_) => ComponentExportKind::Component,
+        }
+    }
+}
+
+impl Encode for ComponentTypeRef {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.kind().encode(sink);
+
+        match self {
+            Self::Module(idx) | Self::Func(idx) | Self::Instance(idx) | Self::Component(idx) => {
+                idx.encode(sink);
+            }
+            Self::Value(ty) => ty.encode(sink),
+            Self::Type(bounds, idx) => {
+                bounds.encode(sink);
+                idx.encode(sink);
+            }
+        }
+    }
+}
+
+/// An encoder for the import section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, ComponentTypeSection, PrimitiveValType, ComponentImportSection, ComponentTypeRef};
+///
+/// let mut types = ComponentTypeSection::new();
+///
+/// // Define a function type of `[string, string] -> string`.
+/// types
+///   .function()
+///   .params(
+///     [
+///       ("a", PrimitiveValType::String),
+///       ("b", PrimitiveValType::String)
+///     ]
+///   )
+///   .result(PrimitiveValType::String);
+///
+/// // This imports a function named `f` with the type defined above
+/// let mut imports = ComponentImportSection::new();
+/// imports.import("f", "", ComponentTypeRef::Func(0));
+///
+/// let mut component = Component::new();
+/// component.section(&types);
+/// component.section(&imports);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct ComponentImportSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl ComponentImportSection {
+    /// Create a new component import section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of imports in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an import in the component import section.
+    pub fn import(&mut self, name: &str, url: &str, ty: ComponentTypeRef) -> &mut Self {
+        name.encode(&mut self.bytes);
+        url.encode(&mut self.bytes);
+        ty.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for ComponentImportSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for ComponentImportSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::Import.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/instances.rs b/third_party/rust/wasm-encoder/src/component/instances.rs
new file mode 100644
index 0000000000..5f2c97dec3
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/instances.rs
@@ -0,0 +1,199 @@
+use super::CORE_INSTANCE_SORT;
+use crate::{
+    encode_section, ComponentExportKind, ComponentSection, ComponentSectionId, Encode, ExportKind,
+};
+
+/// Represents an argument to a module instantiation.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum ModuleArg {
+    /// The argument is an instance.
+    Instance(u32),
+}
+
+impl Encode for ModuleArg {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        let (sort, idx) = match self {
+            Self::Instance(idx) => (CORE_INSTANCE_SORT, *idx),
+        };
+        sink.push(sort);
+        idx.encode(sink);
+    }
+}
+
+/// An encoder for the core instance section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, InstanceSection, ExportKind, ModuleArg};
+///
+/// let mut instances = InstanceSection::new();
+/// instances.export_items([("foo", ExportKind::Func, 0)]);
+/// instances.instantiate(1, [("foo", ModuleArg::Instance(0))]);
+///
+/// let mut component = Component::new();
+/// component.section(&instances);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct InstanceSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl InstanceSection {
+    /// Create a new core instance section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of instances in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an instance by instantiating a core module.
+    pub fn instantiate<A, S>(&mut self, module_index: u32, args: A) -> &mut Self
+    where
+        A: IntoIterator<Item = (S, ModuleArg)>,
+        A::IntoIter: ExactSizeIterator,
+        S: AsRef<str>,
+    {
+        let args = args.into_iter();
+        self.bytes.push(0x00);
+        module_index.encode(&mut self.bytes);
+        args.len().encode(&mut self.bytes);
+        for (name, arg) in args {
+            name.as_ref().encode(&mut self.bytes);
+            arg.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+
+    /// Define an instance by exporting core WebAssembly items.
+    pub fn export_items<E, S>(&mut self, exports: E) -> &mut Self
+    where
+        E: IntoIterator<Item = (S, ExportKind, u32)>,
+        E::IntoIter: ExactSizeIterator,
+        S: AsRef<str>,
+    {
+        let exports = exports.into_iter();
+        self.bytes.push(0x01);
+        exports.len().encode(&mut self.bytes);
+        for (name, kind, index) in exports {
+            name.as_ref().encode(&mut self.bytes);
+            kind.encode(&mut self.bytes);
+            index.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for InstanceSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for InstanceSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::CoreInstance.into()
+    }
+}
+
+/// An encoder for the instance section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, ComponentInstanceSection, ComponentExportKind};
+///
+/// let mut instances = ComponentInstanceSection::new();
+/// instances.export_items([("foo", ComponentExportKind::Func, 0)]);
+/// instances.instantiate(1, [("foo", ComponentExportKind::Instance, 0)]);
+///
+/// let mut component = Component::new();
+/// component.section(&instances);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct ComponentInstanceSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl ComponentInstanceSection {
+    /// Create a new instance section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of instances in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an instance by instantiating a component.
+    pub fn instantiate<A, S>(&mut self, component_index: u32, args: A) -> &mut Self
+    where
+        A: IntoIterator<Item = (S, ComponentExportKind, u32)>,
+        A::IntoIter: ExactSizeIterator,
+        S: AsRef<str>,
+    {
+        let args = args.into_iter();
+        self.bytes.push(0x00);
+        component_index.encode(&mut self.bytes);
+        args.len().encode(&mut self.bytes);
+        for (name, kind, index) in args {
+            name.as_ref().encode(&mut self.bytes);
+            kind.encode(&mut self.bytes);
+            index.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+
+    /// Define an instance by exporting items.
+    pub fn export_items<'a, E>(&mut self, exports: E) -> &mut Self
+    where
+        E: IntoIterator<Item = (&'a str, ComponentExportKind, u32)>,
+        E::IntoIter: ExactSizeIterator,
+    {
+        let exports = exports.into_iter();
+        self.bytes.push(0x01);
+        exports.len().encode(&mut self.bytes);
+        for (name, kind, index) in exports {
+            name.encode(&mut self.bytes);
+            kind.encode(&mut self.bytes);
+            index.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for ComponentInstanceSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for ComponentInstanceSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::Instance.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/modules.rs b/third_party/rust/wasm-encoder/src/component/modules.rs
new file mode 100644
index 0000000000..437cd353af
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/modules.rs
@@ -0,0 +1,29 @@
+use crate::{ComponentSection, ComponentSectionId, Encode, Module};
+
+/// An encoder for the module section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Module, Component, ModuleSection};
+///
+/// let mut module = Module::new();
+/// let mut component = Component::new();
+/// component.section(&ModuleSection(&module));
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug)]
+pub struct ModuleSection<'a>(pub &'a Module);
+
+impl Encode for ModuleSection<'_> {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.0.bytes.encode(sink);
+    }
+}
+
+impl ComponentSection for ModuleSection<'_> {
+    fn id(&self) -> u8 {
+        ComponentSectionId::CoreModule.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/names.rs b/third_party/rust/wasm-encoder/src/component/names.rs
new file mode 100644
index 0000000000..0e3b02dc2e
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/names.rs
@@ -0,0 +1,147 @@
+use super::*;
+use crate::{encoding_size, CustomSection, Encode, ExportKind, NameMap, SectionId};
+
+/// Encoding for the `component-name` custom section which assigns
+/// human-readable names to items within a component.
+#[derive(Clone, Debug, Default)]
+pub struct ComponentNameSection {
+    bytes: Vec<u8>,
+}
+
+enum Subsection {
+    Component,
+    Decls,
+}
+
+impl ComponentNameSection {
+    /// Creates a new blank `name` custom section.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Appends a component name subsection to this section.
+    ///
+    /// This will indicate that the name of the entire component should be the
+    /// `name` specified. Note that this should be encoded first before other
+    /// subsections.
+    pub fn component(&mut self, name: &str) {
+        let len = encoding_size(u32::try_from(name.len()).unwrap());
+        self.subsection_header(Subsection::Component, len + name.len());
+        name.encode(&mut self.bytes);
+    }
+
+    /// Appends a decls name subsection to name core functions within the
+    /// component.
+    pub fn core_funcs(&mut self, names: &NameMap) {
+        self.core_decls(ExportKind::Func as u8, names)
+    }
+
+    /// Appends a decls name subsection to name core tables within the
+    /// component.
+    pub fn core_tables(&mut self, names: &NameMap) {
+        self.core_decls(ExportKind::Table as u8, names)
+    }
+
+    /// Appends a decls name subsection to name core memories within the
+    /// component.
+    pub fn core_memories(&mut self, names: &NameMap) {
+        self.core_decls(ExportKind::Memory as u8, names)
+    }
+
+    /// Appends a decls name subsection to name core globals within the
+    /// component.
+    pub fn core_globals(&mut self, names: &NameMap) {
+        self.core_decls(ExportKind::Global as u8, names)
+    }
+
+    /// Appends a decls name subsection to name core types within the
+    /// component.
+    pub fn core_types(&mut self, names: &NameMap) {
+        self.core_decls(CORE_TYPE_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name core modules within the
+    /// component.
+    pub fn core_modules(&mut self, names: &NameMap) {
+        self.core_decls(CORE_MODULE_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name core instances within the
+    /// component.
+    pub fn core_instances(&mut self, names: &NameMap) {
+        self.core_decls(CORE_INSTANCE_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name component functions within the
+    /// component.
+    pub fn funcs(&mut self, names: &NameMap) {
+        self.component_decls(FUNCTION_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name component values within the
+    /// component.
+    pub fn values(&mut self, names: &NameMap) {
+        self.component_decls(VALUE_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name component type within the
+    /// component.
+    pub fn types(&mut self, names: &NameMap) {
+        self.component_decls(TYPE_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name components within the
+    /// component.
+    pub fn components(&mut self, names: &NameMap) {
+        self.component_decls(COMPONENT_SORT, names)
+    }
+
+    /// Appends a decls name subsection to name component instances within the
+    /// component.
+    pub fn instances(&mut self, names: &NameMap) {
+        self.component_decls(INSTANCE_SORT, names)
+    }
+
+    fn component_decls(&mut self, kind: u8, names: &NameMap) {
+        self.subsection_header(Subsection::Decls, 1 + names.size());
+        self.bytes.push(kind);
+        names.encode(&mut self.bytes);
+    }
+
+    fn core_decls(&mut self, kind: u8, names: &NameMap) {
+        self.subsection_header(Subsection::Decls, 2 + names.size());
+        self.bytes.push(CORE_SORT);
+        self.bytes.push(kind);
+        names.encode(&mut self.bytes);
+    }
+
+    fn subsection_header(&mut self, id: Subsection, len: usize) {
+        self.bytes.push(id as u8);
+        len.encode(&mut self.bytes);
+    }
+
+    /// Returns whether this section is empty, or nothing has been encoded.
+    pub fn is_empty(&self) -> bool {
+        self.bytes.is_empty()
+    }
+
+    /// View the encoded section as a CustomSection.
+    pub fn as_custom<'a>(&'a self) -> CustomSection<'a> {
+        CustomSection {
+            name: "component-name",
+            data: &self.bytes,
+        }
+    }
+}
+
+impl Encode for ComponentNameSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.as_custom().encode(sink);
+    }
+}
+
+impl ComponentSection for ComponentNameSection {
+    fn id(&self) -> u8 {
+        SectionId::Custom.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/start.rs b/third_party/rust/wasm-encoder/src/component/start.rs
new file mode 100644
index 0000000000..d4b60e1dfc
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/start.rs
@@ -0,0 +1,52 @@
+use crate::{ComponentSection, ComponentSectionId, Encode};
+
+/// An encoder for the start section of WebAssembly components.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{Component, ComponentStartSection};
+///
+/// let start = ComponentStartSection { function_index: 0, args: [0, 1], results: 1 };
+///
+/// let mut component = Component::new();
+/// component.section(&start);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug)]
+pub struct ComponentStartSection<A> {
+    /// The index to the start function.
+    pub function_index: u32,
+    /// The arguments to pass to the start function.
+    ///
+    /// An argument is an index to a value.
+    pub args: A,
+    /// The number of expected results for the start function.
+    ///
+    /// This should match the number of results for the type of
+    /// the function referenced by `function_index`.
+    pub results: u32,
+}
+
+impl<A> Encode for ComponentStartSection<A>
+where
+    A: AsRef<[u32]>,
+{
+    fn encode(&self, sink: &mut Vec<u8>) {
+        let mut bytes = Vec::new();
+        self.function_index.encode(&mut bytes);
+        self.args.as_ref().encode(&mut bytes);
+        self.results.encode(&mut bytes);
+        bytes.encode(sink);
+    }
+}
+
+impl<A> ComponentSection for ComponentStartSection<A>
+where
+    A: AsRef<[u32]>,
+{
+    fn id(&self) -> u8 {
+        ComponentSectionId::Start.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/component/types.rs b/third_party/rust/wasm-encoder/src/component/types.rs
new file mode 100644
index 0000000000..930467d57a
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/types.rs
@@ -0,0 +1,736 @@
+use super::CORE_TYPE_SORT;
+use crate::{
+    encode_section, Alias, ComponentExportKind, ComponentOuterAliasKind, ComponentSection,
+    ComponentSectionId, ComponentTypeRef, Encode, EntityType, ValType,
+};
+
+/// Represents the type of a core module.
+#[derive(Debug, Clone, Default)]
+pub struct ModuleType {
+    bytes: Vec<u8>,
+    num_added: u32,
+    types_added: u32,
+}
+
+impl ModuleType {
+    /// Creates a new core module type.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Defines an import in this module type.
+    pub fn import(&mut self, module: &str, name: &str, ty: EntityType) -> &mut Self {
+        self.bytes.push(0x00);
+        module.encode(&mut self.bytes);
+        name.encode(&mut self.bytes);
+        ty.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+
+    /// Define a type in this module type.
+    ///
+    /// The returned encoder must be used before adding another definition.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn ty(&mut self) -> CoreTypeEncoder {
+        self.bytes.push(0x01);
+        self.num_added += 1;
+        self.types_added += 1;
+        CoreTypeEncoder(&mut self.bytes)
+    }
+
+    /// Defines an outer core type alias in this module type.
+    pub fn alias_outer_core_type(&mut self, count: u32, index: u32) -> &mut Self {
+        self.bytes.push(0x02);
+        self.bytes.push(CORE_TYPE_SORT);
+        self.bytes.push(0x01); // outer
+        count.encode(&mut self.bytes);
+        index.encode(&mut self.bytes);
+        self.num_added += 1;
+        self.types_added += 1;
+        self
+    }
+
+    /// Defines an export in this module type.
+    pub fn export(&mut self, name: &str, ty: EntityType) -> &mut Self {
+        self.bytes.push(0x03);
+        name.encode(&mut self.bytes);
+        ty.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+
+    /// Gets the number of types that have been added to this module type.
+    pub fn type_count(&self) -> u32 {
+        self.types_added
+    }
+}
+
+impl Encode for ModuleType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(0x50);
+        self.num_added.encode(sink);
+        sink.extend(&self.bytes);
+    }
+}
+
+/// Used to encode core types.
+#[derive(Debug)]
+pub struct CoreTypeEncoder<'a>(pub(crate) &'a mut Vec<u8>);
+
+impl<'a> CoreTypeEncoder<'a> {
+    /// Define a function type.
+    pub fn function<P, R>(self, params: P, results: R)
+    where
+        P: IntoIterator<Item = ValType>,
+        P::IntoIter: ExactSizeIterator,
+        R: IntoIterator<Item = ValType>,
+        R::IntoIter: ExactSizeIterator,
+    {
+        let params = params.into_iter();
+        let results = results.into_iter();
+
+        self.0.push(0x60);
+        params.len().encode(self.0);
+        params.for_each(|p| p.encode(self.0));
+        results.len().encode(self.0);
+        results.for_each(|p| p.encode(self.0));
+    }
+
+    /// Define a module type.
+    pub fn module(self, ty: &ModuleType) {
+        ty.encode(self.0);
+    }
+}
+
+/// An encoder for the core type section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, CoreTypeSection, ModuleType};
+///
+/// let mut types = CoreTypeSection::new();
+///
+/// types.module(&ModuleType::new());
+///
+/// let mut component = Component::new();
+/// component.section(&types);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct CoreTypeSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl CoreTypeSection {
+    /// Create a new core type section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of types in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Encode a type into this section.
+    ///
+    /// The returned encoder must be finished before adding another type.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn ty(&mut self) -> CoreTypeEncoder<'_> {
+        self.num_added += 1;
+        CoreTypeEncoder(&mut self.bytes)
+    }
+
+    /// Define a function type in this type section.
+    pub fn function<P, R>(&mut self, params: P, results: R) -> &mut Self
+    where
+        P: IntoIterator<Item = ValType>,
+        P::IntoIter: ExactSizeIterator,
+        R: IntoIterator<Item = ValType>,
+        R::IntoIter: ExactSizeIterator,
+    {
+        self.ty().function(params, results);
+        self
+    }
+
+    /// Define a module type in this type section.
+    ///
+    /// Currently this is only used for core type sections in components.
+    pub fn module(&mut self, ty: &ModuleType) -> &mut Self {
+        self.ty().module(ty);
+        self
+    }
+}
+
+impl Encode for CoreTypeSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for CoreTypeSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::CoreType.into()
+    }
+}
+
+/// Represents a component type.
+#[derive(Debug, Clone, Default)]
+pub struct ComponentType {
+    bytes: Vec<u8>,
+    num_added: u32,
+    core_types_added: u32,
+    types_added: u32,
+}
+
+impl ComponentType {
+    /// Creates a new component type.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Define a core type in this component type.
+    ///
+    /// The returned encoder must be used before adding another definition.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn core_type(&mut self) -> CoreTypeEncoder {
+        self.bytes.push(0x00);
+        self.num_added += 1;
+        self.core_types_added += 1;
+        CoreTypeEncoder(&mut self.bytes)
+    }
+
+    /// Define a type in this component type.
+    ///
+    /// The returned encoder must be used before adding another definition.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn ty(&mut self) -> ComponentTypeEncoder {
+        self.bytes.push(0x01);
+        self.num_added += 1;
+        self.types_added += 1;
+        ComponentTypeEncoder(&mut self.bytes)
+    }
+
+    /// Defines an alias for an exported item of a prior instance or an
+    /// outer type.
+    pub fn alias(&mut self, alias: Alias<'_>) -> &mut Self {
+        self.bytes.push(0x02);
+        alias.encode(&mut self.bytes);
+        self.num_added += 1;
+        match &alias {
+            Alias::InstanceExport {
+                kind: ComponentExportKind::Type,
+                ..
+            }
+            | Alias::Outer {
+                kind: ComponentOuterAliasKind::Type,
+                ..
+            } => self.types_added += 1,
+            Alias::Outer {
+                kind: ComponentOuterAliasKind::CoreType,
+                ..
+            } => self.core_types_added += 1,
+            _ => {}
+        }
+        self
+    }
+
+    /// Defines an import in this component type.
+    pub fn import(&mut self, name: &str, url: &str, ty: ComponentTypeRef) -> &mut Self {
+        self.bytes.push(0x03);
+        name.encode(&mut self.bytes);
+        url.encode(&mut self.bytes);
+        ty.encode(&mut self.bytes);
+        self.num_added += 1;
+        match ty {
+            ComponentTypeRef::Type(..) => self.types_added += 1,
+            _ => {}
+        }
+        self
+    }
+
+    /// Defines an export in this component type.
+    pub fn export(&mut self, name: &str, url: &str, ty: ComponentTypeRef) -> &mut Self {
+        self.bytes.push(0x04);
+        name.encode(&mut self.bytes);
+        url.encode(&mut self.bytes);
+        ty.encode(&mut self.bytes);
+        self.num_added += 1;
+        match ty {
+            ComponentTypeRef::Type(..) => self.types_added += 1,
+            _ => {}
+        }
+        self
+    }
+
+    /// Gets the number of core types that have been added to this component type.
+    pub fn core_type_count(&self) -> u32 {
+        self.core_types_added
+    }
+
+    /// Gets the number of types that have been added or aliased in this component type.
+    pub fn type_count(&self) -> u32 {
+        self.types_added
+    }
+}
+
+impl Encode for ComponentType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(0x41);
+        self.num_added.encode(sink);
+        sink.extend(&self.bytes);
+    }
+}
+
+/// Represents an instance type.
+#[derive(Debug, Clone, Default)]
+pub struct InstanceType(ComponentType);
+
+impl InstanceType {
+    /// Creates a new instance type.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Define a core type in this instance type.
+    ///
+    /// The returned encoder must be used before adding another definition.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn core_type(&mut self) -> CoreTypeEncoder {
+        self.0.core_type()
+    }
+
+    /// Define a type in this instance type.
+    ///
+    /// The returned encoder must be used before adding another definition.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn ty(&mut self) -> ComponentTypeEncoder {
+        self.0.ty()
+    }
+
+    /// Defines an outer core type alias in this component type.
+    pub fn alias(&mut self, alias: Alias<'_>) -> &mut Self {
+        self.0.alias(alias);
+        self
+    }
+
+    /// Defines an export in this instance type.
+    pub fn export(&mut self, name: &str, url: &str, ty: ComponentTypeRef) -> &mut Self {
+        self.0.export(name, url, ty);
+        self
+    }
+
+    /// Gets the number of core types that have been added to this instance type.
+    pub fn core_type_count(&self) -> u32 {
+        self.0.core_types_added
+    }
+
+    /// Gets the number of types that have been added or aliased in this instance type.
+    pub fn type_count(&self) -> u32 {
+        self.0.types_added
+    }
+
+    /// Returns whether or not this instance type is empty.
+    pub fn is_empty(&self) -> bool {
+        self.0.num_added == 0
+    }
+
+    /// Returns the number of entries added to this instance types.
+    pub fn len(&self) -> u32 {
+        self.0.num_added
+    }
+}
+
+impl Encode for InstanceType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(0x42);
+        self.0.num_added.encode(sink);
+        sink.extend(&self.0.bytes);
+    }
+}
+
+/// Used to encode component function types.
+#[derive(Debug)]
+pub struct ComponentFuncTypeEncoder<'a>(&'a mut Vec<u8>);
+
+impl<'a> ComponentFuncTypeEncoder<'a> {
+    fn new(sink: &'a mut Vec<u8>) -> Self {
+        sink.push(0x40);
+        Self(sink)
+    }
+
+    /// Defines named parameters.
+    ///
+    /// Parameters must be defined before defining results.
+    pub fn params<'b, P, T>(&mut self, params: P) -> &mut Self
+    where
+        P: IntoIterator<Item = (&'b str, T)>,
+        P::IntoIter: ExactSizeIterator,
+        T: Into<ComponentValType>,
+    {
+        let params = params.into_iter();
+        params.len().encode(self.0);
+        for (name, ty) in params {
+            name.encode(self.0);
+            ty.into().encode(self.0);
+        }
+        self
+    }
+
+    /// Defines a single unnamed result.
+    ///
+    /// This method cannot be used with `results`.
+    pub fn result(&mut self, ty: impl Into<ComponentValType>) -> &mut Self {
+        self.0.push(0x00);
+        ty.into().encode(self.0);
+        self
+    }
+
+    /// Defines named results.
+    ///
+    /// This method cannot be used with `result`.
+    pub fn results<'b, R, T>(&mut self, results: R) -> &mut Self
+    where
+        R: IntoIterator<Item = (&'b str, T)>,
+        R::IntoIter: ExactSizeIterator,
+        T: Into<ComponentValType>,
+    {
+        self.0.push(0x01);
+        let results = results.into_iter();
+        results.len().encode(self.0);
+        for (name, ty) in results {
+            name.encode(self.0);
+            ty.into().encode(self.0);
+        }
+        self
+    }
+}
+
+/// Used to encode component and instance types.
+#[derive(Debug)]
+pub struct ComponentTypeEncoder<'a>(&'a mut Vec<u8>);
+
+impl<'a> ComponentTypeEncoder<'a> {
+    /// Define a component type.
+    pub fn component(self, ty: &ComponentType) {
+        ty.encode(self.0);
+    }
+
+    /// Define an instance type.
+    pub fn instance(self, ty: &InstanceType) {
+        ty.encode(self.0);
+    }
+
+    /// Define a function type.
+    pub fn function(self) -> ComponentFuncTypeEncoder<'a> {
+        ComponentFuncTypeEncoder::new(self.0)
+    }
+
+    /// Define a defined component type.
+    ///
+    /// The returned encoder must be used before adding another type.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn defined_type(self) -> ComponentDefinedTypeEncoder<'a> {
+        ComponentDefinedTypeEncoder(self.0)
+    }
+}
+
+/// Represents a primitive component value type.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum PrimitiveValType {
+    /// The type is a boolean.
+    Bool,
+    /// The type is a signed 8-bit integer.
+    S8,
+    /// The type is an unsigned 8-bit integer.
+    U8,
+    /// The type is a signed 16-bit integer.
+    S16,
+    /// The type is an unsigned 16-bit integer.
+    U16,
+    /// The type is a signed 32-bit integer.
+    S32,
+    /// The type is an unsigned 32-bit integer.
+    U32,
+    /// The type is a signed 64-bit integer.
+    S64,
+    /// The type is an unsigned 64-bit integer.
+    U64,
+    /// The type is a 32-bit floating point number.
+    Float32,
+    /// The type is a 64-bit floating point number.
+    Float64,
+    /// The type is a Unicode character.
+    Char,
+    /// The type is a string.
+    String,
+}
+
+impl Encode for PrimitiveValType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(match self {
+            Self::Bool => 0x7f,
+            Self::S8 => 0x7e,
+            Self::U8 => 0x7d,
+            Self::S16 => 0x7c,
+            Self::U16 => 0x7b,
+            Self::S32 => 0x7a,
+            Self::U32 => 0x79,
+            Self::S64 => 0x78,
+            Self::U64 => 0x77,
+            Self::Float32 => 0x76,
+            Self::Float64 => 0x75,
+            Self::Char => 0x74,
+            Self::String => 0x73,
+        });
+    }
+}
+
+/// Represents a component value type.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum ComponentValType {
+    /// The value is a primitive type.
+    Primitive(PrimitiveValType),
+    /// The value is to a defined value type.
+    ///
+    /// The type index must be to a value type.
+    Type(u32),
+}
+
+impl Encode for ComponentValType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Self::Primitive(ty) => ty.encode(sink),
+            Self::Type(index) => (*index as i64).encode(sink),
+        }
+    }
+}
+
+impl From<PrimitiveValType> for ComponentValType {
+    fn from(ty: PrimitiveValType) -> Self {
+        Self::Primitive(ty)
+    }
+}
+
+/// Used for encoding component defined types.
+#[derive(Debug)]
+pub struct ComponentDefinedTypeEncoder<'a>(&'a mut Vec<u8>);
+
+impl ComponentDefinedTypeEncoder<'_> {
+    /// Define a primitive value type.
+    pub fn primitive(self, ty: PrimitiveValType) {
+        ty.encode(self.0);
+    }
+
+    /// Define a record type.
+    pub fn record<'a, F, T>(self, fields: F)
+    where
+        F: IntoIterator<Item = (&'a str, T)>,
+        F::IntoIter: ExactSizeIterator,
+        T: Into<ComponentValType>,
+    {
+        let fields = fields.into_iter();
+        self.0.push(0x72);
+        fields.len().encode(self.0);
+        for (name, ty) in fields {
+            name.encode(self.0);
+            ty.into().encode(self.0);
+        }
+    }
+
+    /// Define a variant type.
+    pub fn variant<'a, C>(self, cases: C)
+    where
+        C: IntoIterator<Item = (&'a str, Option<ComponentValType>, Option<u32>)>,
+        C::IntoIter: ExactSizeIterator,
+    {
+        let cases = cases.into_iter();
+        self.0.push(0x71);
+        cases.len().encode(self.0);
+        for (name, ty, refines) in cases {
+            name.encode(self.0);
+            ty.encode(self.0);
+            refines.encode(self.0);
+        }
+    }
+
+    /// Define a list type.
+    pub fn list(self, ty: impl Into<ComponentValType>) {
+        self.0.push(0x70);
+        ty.into().encode(self.0);
+    }
+
+    /// Define a tuple type.
+    pub fn tuple<I, T>(self, types: I)
+    where
+        I: IntoIterator<Item = T>,
+        I::IntoIter: ExactSizeIterator,
+        T: Into<ComponentValType>,
+    {
+        let types = types.into_iter();
+        self.0.push(0x6F);
+        types.len().encode(self.0);
+        for ty in types {
+            ty.into().encode(self.0);
+        }
+    }
+
+    /// Define a flags type.
+    pub fn flags<'a, I>(self, names: I)
+    where
+        I: IntoIterator<Item = &'a str>,
+        I::IntoIter: ExactSizeIterator,
+    {
+        let names = names.into_iter();
+        self.0.push(0x6E);
+        names.len().encode(self.0);
+        for name in names {
+            name.encode(self.0);
+        }
+    }
+
+    /// Define an enum type.
+    pub fn enum_type<'a, I>(self, tags: I)
+    where
+        I: IntoIterator<Item = &'a str>,
+        I::IntoIter: ExactSizeIterator,
+    {
+        let tags = tags.into_iter();
+        self.0.push(0x6D);
+        tags.len().encode(self.0);
+        for tag in tags {
+            tag.encode(self.0);
+        }
+    }
+
+    /// Define a union type.
+    pub fn union<I, T>(self, types: I)
+    where
+        I: IntoIterator<Item = T>,
+        I::IntoIter: ExactSizeIterator,
+        T: Into<ComponentValType>,
+    {
+        let types = types.into_iter();
+        self.0.push(0x6C);
+        types.len().encode(self.0);
+        for ty in types {
+            ty.into().encode(self.0);
+        }
+    }
+
+    /// Define an option type.
+    pub fn option(self, ty: impl Into<ComponentValType>) {
+        self.0.push(0x6B);
+        ty.into().encode(self.0);
+    }
+
+    /// Define a result type.
+    pub fn result(self, ok: Option<ComponentValType>, err: Option<ComponentValType>) {
+        self.0.push(0x6A);
+        ok.encode(self.0);
+        err.encode(self.0);
+    }
+}
+
+/// An encoder for the type section of WebAssembly components.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Component, ComponentTypeSection, PrimitiveValType};
+///
+/// let mut types = ComponentTypeSection::new();
+///
+/// // Define a function type of `[string, string] -> string`.
+/// types
+///   .function()
+///   .params(
+///     [
+///       ("a", PrimitiveValType::String),
+///       ("b", PrimitiveValType::String)
+///     ]
+///   )
+///   .result(PrimitiveValType::String);
+///
+/// let mut component = Component::new();
+/// component.section(&types);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct ComponentTypeSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl ComponentTypeSection {
+    /// Create a new component type section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of types in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Encode a type into this section.
+    ///
+    /// The returned encoder must be finished before adding another type.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn ty(&mut self) -> ComponentTypeEncoder<'_> {
+        self.num_added += 1;
+        ComponentTypeEncoder(&mut self.bytes)
+    }
+
+    /// Define a component type in this type section.
+    pub fn component(&mut self, ty: &ComponentType) -> &mut Self {
+        self.ty().component(ty);
+        self
+    }
+
+    /// Define an instance type in this type section.
+    pub fn instance(&mut self, ty: &InstanceType) -> &mut Self {
+        self.ty().instance(ty);
+        self
+    }
+
+    /// Define a function type in this type section.
+    pub fn function(&mut self) -> ComponentFuncTypeEncoder<'_> {
+        self.ty().function()
+    }
+
+    /// Add a component defined type to this type section.
+    ///
+    /// The returned encoder must be used before adding another type.
+    #[must_use = "the encoder must be used to encode the type"]
+    pub fn defined_type(&mut self) -> ComponentDefinedTypeEncoder<'_> {
+        self.ty().defined_type()
+    }
+}
+
+impl Encode for ComponentTypeSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for ComponentTypeSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::Type.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core.rs b/third_party/rust/wasm-encoder/src/core.rs
new file mode 100644
index 0000000000..dcf4d6fb74
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core.rs
@@ -0,0 +1,166 @@
+mod code;
+mod custom;
+mod data;
+mod elements;
+mod exports;
+mod functions;
+mod globals;
+mod imports;
+mod linking;
+mod memories;
+mod names;
+mod producers;
+mod start;
+mod tables;
+mod tags;
+mod types;
+
+pub use code::*;
+pub use custom::*;
+pub use data::*;
+pub use elements::*;
+pub use exports::*;
+pub use functions::*;
+pub use globals::*;
+pub use imports::*;
+pub use linking::*;
+pub use memories::*;
+pub use names::*;
+pub use producers::*;
+pub use start::*;
+pub use tables::*;
+pub use tags::*;
+pub use types::*;
+
+use crate::Encode;
+
+pub(crate) const CORE_FUNCTION_SORT: u8 = 0x00;
+pub(crate) const CORE_TABLE_SORT: u8 = 0x01;
+pub(crate) const CORE_MEMORY_SORT: u8 = 0x02;
+pub(crate) const CORE_GLOBAL_SORT: u8 = 0x03;
+pub(crate) const CORE_TAG_SORT: u8 = 0x04;
+
+/// A WebAssembly module section.
+///
+/// Various builders defined in this crate already implement this trait, but you
+/// can also implement it yourself for your own custom section builders, or use
+/// `RawSection` to use a bunch of raw bytes as a section.
+pub trait Section: Encode {
+    /// Gets the section identifier for this section.
+    fn id(&self) -> u8;
+
+    /// Appends this section to the specified destination list of bytes.
+    fn append_to(&self, dst: &mut Vec<u8>) {
+        dst.push(self.id());
+        self.encode(dst);
+    }
+}
+
+/// Known section identifiers of WebAssembly modules.
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd)]
+#[repr(u8)]
+pub enum SectionId {
+    /// The custom section.
+    Custom = 0,
+    /// The type section.
+    Type = 1,
+    /// The import section.
+    Import = 2,
+    /// The function section.
+    Function = 3,
+    /// The table section.
+    Table = 4,
+    /// The memory section.
+    Memory = 5,
+    /// The global section.
+    Global = 6,
+    /// The export section.
+    Export = 7,
+    /// The start section.
+    Start = 8,
+    /// The element section.
+    Element = 9,
+    /// The code section.
+    Code = 10,
+    /// The data section.
+    Data = 11,
+    /// The data count section.
+    DataCount = 12,
+    /// The tag section.
+    ///
+    /// This section is supported by the exception handling proposal.
+    Tag = 13,
+}
+
+impl From<SectionId> for u8 {
+    #[inline]
+    fn from(id: SectionId) -> u8 {
+        id as u8
+    }
+}
+
+impl Encode for SectionId {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(*self as u8);
+    }
+}
+
+/// Represents a WebAssembly component that is being encoded.
+///
+/// Sections within a WebAssembly module are encoded in a specific order.
+///
+/// Modules may also added as a section to a WebAssembly component.
+#[derive(Clone, Debug)]
+pub struct Module {
+    pub(crate) bytes: Vec<u8>,
+}
+
+impl Module {
+    /// The 8-byte header at the beginning of all core wasm modules.
+    #[rustfmt::skip]
+    pub const HEADER: [u8; 8] = [
+        // Magic
+        0x00, 0x61, 0x73, 0x6D,
+        // Version
+        0x01, 0x00, 0x00, 0x00,
+    ];
+
+    /// Begin writing a new `Module`.
+    #[rustfmt::skip]
+    pub fn new() -> Self {
+        Module {
+            bytes: Self::HEADER.to_vec(),
+        }
+    }
+
+    /// Write a section into this module.
+    ///
+    /// It is your responsibility to define the sections in the [proper
+    /// order](https://webassembly.github.io/spec/core/binary/modules.html#binary-module),
+    /// and to ensure that each kind of section (other than custom sections) is
+    /// only defined once. While this is a potential footgun, it also allows you
+    /// to use this crate to easily construct test cases for bad Wasm module
+    /// encodings.
+    pub fn section(&mut self, section: &impl Section) -> &mut Self {
+        self.bytes.push(section.id());
+        section.encode(&mut self.bytes);
+        self
+    }
+
+    /// Get the encoded Wasm module as a slice.
+    pub fn as_slice(&self) -> &[u8] {
+        &self.bytes
+    }
+
+    /// Finish writing this Wasm module and extract ownership of the encoded
+    /// bytes.
+    pub fn finish(self) -> Vec<u8> {
+        self.bytes
+    }
+}
+
+impl Default for Module {
+    fn default() -> Self {
+        Self::new()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/code.rs b/third_party/rust/wasm-encoder/src/core/code.rs
new file mode 100644
index 0000000000..641231d04f
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/code.rs
@@ -0,0 +1,2894 @@
+use crate::{encode_section, Encode, HeapType, Section, SectionId, ValType};
+use std::borrow::Cow;
+
+/// An encoder for the code section.
+///
+/// Code sections are only supported for modules.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{
+///     CodeSection, Function, FunctionSection, Instruction, Module,
+///     TypeSection, ValType
+/// };
+///
+/// let mut types = TypeSection::new();
+/// types.function(vec![], vec![ValType::I32]);
+///
+/// let mut functions = FunctionSection::new();
+/// let type_index = 0;
+/// functions.function(type_index);
+///
+/// let locals = vec![];
+/// let mut func = Function::new(locals);
+/// func.instruction(&Instruction::I32Const(42));
+/// let mut code = CodeSection::new();
+/// code.function(&func);
+///
+/// let mut module = Module::new();
+/// module
+///     .section(&types)
+///     .section(&functions)
+///     .section(&code);
+///
+/// let wasm_bytes = module.finish();
+/// ```
+#[derive(Clone, Default, Debug)]
+pub struct CodeSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl CodeSection {
+    /// Create a new code section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of functions in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// The number of bytes already added to this section.
+    ///
+    /// This number doesn't include the vector length that precedes the
+    /// code entries, since it has a variable size that isn't known until all
+    /// functions are added.
+    pub fn byte_len(&self) -> usize {
+        self.bytes.len()
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Write a function body into this code section.
+    pub fn function(&mut self, func: &Function) -> &mut Self {
+        func.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+
+    /// Add a raw byte slice into this code section as a function body.
+    ///
+    /// The length prefix of the function body will be automatically prepended,
+    /// and should not be included in the raw byte slice.
+    ///
+    /// # Example
+    ///
+    /// You can use the `raw` method to copy an already-encoded function body
+    /// into a new code section encoder:
+    ///
+    /// ```
+    /// //                  id, size, # entries, entry
+    /// let code_section = [10, 6,    1,         4, 0, 65, 0, 11];
+    ///
+    /// // Parse the code section.
+    /// let reader = wasmparser::CodeSectionReader::new(&code_section, 0).unwrap();
+    /// let body = reader.into_iter().next().unwrap().unwrap();
+    /// let body_range = body.range();
+    ///
+    /// // Add the body to a new code section encoder by copying bytes rather
+    /// // than re-parsing and re-encoding it.
+    /// let mut encoder = wasm_encoder::CodeSection::new();
+    /// encoder.raw(&code_section[body_range.start..body_range.end]);
+    /// ```
+    pub fn raw(&mut self, data: &[u8]) -> &mut Self {
+        data.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for CodeSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl Section for CodeSection {
+    fn id(&self) -> u8 {
+        SectionId::Code.into()
+    }
+}
+
+/// An encoder for a function body within the code section.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{CodeSection, Function, Instruction};
+///
+/// // Define the function body for:
+/// //
+/// //     (func (param i32 i32) (result i32)
+/// //       local.get 0
+/// //       local.get 1
+/// //       i32.add)
+/// let locals = vec![];
+/// let mut func = Function::new(locals);
+/// func.instruction(&Instruction::LocalGet(0));
+/// func.instruction(&Instruction::LocalGet(1));
+/// func.instruction(&Instruction::I32Add);
+///
+/// // Add our function to the code section.
+/// let mut code = CodeSection::new();
+/// code.function(&func);
+/// ```
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct Function {
+    bytes: Vec<u8>,
+}
+
+impl Function {
+    /// Create a new function body with the given locals.
+    ///
+    /// The argument is an iterator over `(N, Ty)`, which defines
+    /// that the next `N` locals will be of type `Ty`.
+    ///
+    /// For example, a function with locals 0 and 1 of type I32 and
+    /// local 2 of type F32 would be created as:
+    ///
+    /// ```
+    /// # use wasm_encoder::{Function, ValType};
+    /// let f = Function::new([(2, ValType::I32), (1, ValType::F32)]);
+    /// ```
+    ///
+    /// For more information about the code section (and function definition) in the WASM binary format
+    /// see the [WebAssembly spec](https://webassembly.github.io/spec/core/binary/modules.html#binary-func)
+    pub fn new<L>(locals: L) -> Self
+    where
+        L: IntoIterator<Item = (u32, ValType)>,
+        L::IntoIter: ExactSizeIterator,
+    {
+        let locals = locals.into_iter();
+        let mut bytes = vec![];
+        locals.len().encode(&mut bytes);
+        for (count, ty) in locals {
+            count.encode(&mut bytes);
+            ty.encode(&mut bytes);
+        }
+        Function { bytes }
+    }
+
+    /// Create a function from a list of locals' types.
+    ///
+    /// Unlike [`Function::new`], this constructor simply takes a list of types
+    /// which are in order associated with locals.
+    ///
+    /// For example:
+    ///
+    ///  ```
+    /// # use wasm_encoder::{Function, ValType};
+    /// let f = Function::new([(2, ValType::I32), (1, ValType::F32)]);
+    /// let g = Function::new_with_locals_types([
+    ///     ValType::I32, ValType::I32, ValType::F32
+    /// ]);
+    ///
+    /// assert_eq!(f, g)
+    /// ```
+    pub fn new_with_locals_types<L>(locals: L) -> Self
+    where
+        L: IntoIterator<Item = ValType>,
+    {
+        let locals = locals.into_iter();
+
+        let mut locals_collected: Vec<(u32, ValType)> = vec![];
+        for l in locals {
+            if let Some((last_count, last_type)) = locals_collected.last_mut() {
+                if l == *last_type {
+                    // Increment the count of consecutive locals of this type
+                    *last_count += 1;
+                    continue;
+                }
+            }
+            // If we didn't increment, a new type of local appeared
+            locals_collected.push((1, l));
+        }
+
+        Function::new(locals_collected)
+    }
+
+    /// Write an instruction into this function body.
+    pub fn instruction(&mut self, instruction: &Instruction) -> &mut Self {
+        instruction.encode(&mut self.bytes);
+        self
+    }
+
+    /// Add raw bytes to this function's body.
+    pub fn raw<B>(&mut self, bytes: B) -> &mut Self
+    where
+        B: IntoIterator<Item = u8>,
+    {
+        self.bytes.extend(bytes);
+        self
+    }
+
+    /// The number of bytes already added to this function.
+    ///
+    /// This number doesn't include the variable-width size field that `encode`
+    /// will write before the added bytes, since the size of that field isn't
+    /// known until all the instructions are added to this function.
+    pub fn byte_len(&self) -> usize {
+        self.bytes.len()
+    }
+}
+
+impl Encode for Function {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.bytes.encode(sink);
+    }
+}
+
+/// The immediate for a memory instruction.
+#[derive(Clone, Copy, Debug)]
+pub struct MemArg {
+    /// A static offset to add to the instruction's dynamic address operand.
+    ///
+    /// This is a `u64` field for the memory64 proposal, but 32-bit memories
+    /// limit offsets to at most `u32::MAX` bytes. This will be encoded as a LEB
+    /// but it won't generate a valid module if an offset is specified which is
+    /// larger than the maximum size of the index space for the memory indicated
+    /// by `memory_index`.
+    pub offset: u64,
+    /// The expected alignment of the instruction's dynamic address operand
+    /// (expressed the exponent of a power of two).
+    pub align: u32,
+    /// The index of the memory this instruction is operating upon.
+    pub memory_index: u32,
+}
+
+impl Encode for MemArg {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        if self.memory_index == 0 {
+            self.align.encode(sink);
+            self.offset.encode(sink);
+        } else {
+            (self.align | (1 << 6)).encode(sink);
+            self.memory_index.encode(sink);
+            self.offset.encode(sink);
+        }
+    }
+}
+
+/// Describe an unchecked SIMD lane index.
+pub type Lane = u8;
+
+/// The type for a `block`/`if`/`loop`.
+#[derive(Clone, Copy, Debug)]
+pub enum BlockType {
+    /// `[] -> []`
+    Empty,
+    /// `[] -> [t]`
+    Result(ValType),
+    /// The `n`th function type.
+    FunctionType(u32),
+}
+
+impl Encode for BlockType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match *self {
+            Self::Empty => sink.push(0x40),
+            Self::Result(ty) => ty.encode(sink),
+            Self::FunctionType(f) => (f as i64).encode(sink),
+        }
+    }
+}
+
+/// WebAssembly instructions.
+#[derive(Clone, Debug)]
+#[non_exhaustive]
+#[allow(missing_docs, non_camel_case_types)]
+pub enum Instruction<'a> {
+    // Control instructions.
+    Unreachable,
+    Nop,
+    Block(BlockType),
+    Loop(BlockType),
+    If(BlockType),
+    Else,
+    Try(BlockType),
+    Delegate(u32),
+    Catch(u32),
+    CatchAll,
+    End,
+    Br(u32),
+    BrIf(u32),
+    BrTable(Cow<'a, [u32]>, u32),
+    BrOnNull(u32),
+    BrOnNonNull(u32),
+    Return,
+    Call(u32),
+    CallRef(HeapType),
+    CallIndirect { ty: u32, table: u32 },
+    ReturnCallRef(HeapType),
+    ReturnCall(u32),
+    ReturnCallIndirect { ty: u32, table: u32 },
+    Throw(u32),
+    Rethrow(u32),
+
+    // Parametric instructions.
+    Drop,
+    Select,
+
+    // Variable instructions.
+    LocalGet(u32),
+    LocalSet(u32),
+    LocalTee(u32),
+    GlobalGet(u32),
+    GlobalSet(u32),
+
+    // Memory instructions.
+    I32Load(MemArg),
+    I64Load(MemArg),
+    F32Load(MemArg),
+    F64Load(MemArg),
+    I32Load8S(MemArg),
+    I32Load8U(MemArg),
+    I32Load16S(MemArg),
+    I32Load16U(MemArg),
+    I64Load8S(MemArg),
+    I64Load8U(MemArg),
+    I64Load16S(MemArg),
+    I64Load16U(MemArg),
+    I64Load32S(MemArg),
+    I64Load32U(MemArg),
+    I32Store(MemArg),
+    I64Store(MemArg),
+    F32Store(MemArg),
+    F64Store(MemArg),
+    I32Store8(MemArg),
+    I32Store16(MemArg),
+    I64Store8(MemArg),
+    I64Store16(MemArg),
+    I64Store32(MemArg),
+    MemorySize(u32),
+    MemoryGrow(u32),
+    MemoryInit { mem: u32, data_index: u32 },
+    DataDrop(u32),
+    MemoryCopy { src_mem: u32, dst_mem: u32 },
+    MemoryFill(u32),
+    MemoryDiscard(u32),
+
+    // Numeric instructions.
+    I32Const(i32),
+    I64Const(i64),
+    F32Const(f32),
+    F64Const(f64),
+    I32Eqz,
+    I32Eq,
+    I32Ne,
+    I32LtS,
+    I32LtU,
+    I32GtS,
+    I32GtU,
+    I32LeS,
+    I32LeU,
+    I32GeS,
+    I32GeU,
+    I64Eqz,
+    I64Eq,
+    I64Ne,
+    I64LtS,
+    I64LtU,
+    I64GtS,
+    I64GtU,
+    I64LeS,
+    I64LeU,
+    I64GeS,
+    I64GeU,
+    F32Eq,
+    F32Ne,
+    F32Lt,
+    F32Gt,
+    F32Le,
+    F32Ge,
+    F64Eq,
+    F64Ne,
+    F64Lt,
+    F64Gt,
+    F64Le,
+    F64Ge,
+    I32Clz,
+    I32Ctz,
+    I32Popcnt,
+    I32Add,
+    I32Sub,
+    I32Mul,
+    I32DivS,
+    I32DivU,
+    I32RemS,
+    I32RemU,
+    I32And,
+    I32Or,
+    I32Xor,
+    I32Shl,
+    I32ShrS,
+    I32ShrU,
+    I32Rotl,
+    I32Rotr,
+    I64Clz,
+    I64Ctz,
+    I64Popcnt,
+    I64Add,
+    I64Sub,
+    I64Mul,
+    I64DivS,
+    I64DivU,
+    I64RemS,
+    I64RemU,
+    I64And,
+    I64Or,
+    I64Xor,
+    I64Shl,
+    I64ShrS,
+    I64ShrU,
+    I64Rotl,
+    I64Rotr,
+    F32Abs,
+    F32Neg,
+    F32Ceil,
+    F32Floor,
+    F32Trunc,
+    F32Nearest,
+    F32Sqrt,
+    F32Add,
+    F32Sub,
+    F32Mul,
+    F32Div,
+    F32Min,
+    F32Max,
+    F32Copysign,
+    F64Abs,
+    F64Neg,
+    F64Ceil,
+    F64Floor,
+    F64Trunc,
+    F64Nearest,
+    F64Sqrt,
+    F64Add,
+    F64Sub,
+    F64Mul,
+    F64Div,
+    F64Min,
+    F64Max,
+    F64Copysign,
+    I32WrapI64,
+    I32TruncF32S,
+    I32TruncF32U,
+    I32TruncF64S,
+    I32TruncF64U,
+    I64ExtendI32S,
+    I64ExtendI32U,
+    I64TruncF32S,
+    I64TruncF32U,
+    I64TruncF64S,
+    I64TruncF64U,
+    F32ConvertI32S,
+    F32ConvertI32U,
+    F32ConvertI64S,
+    F32ConvertI64U,
+    F32DemoteF64,
+    F64ConvertI32S,
+    F64ConvertI32U,
+    F64ConvertI64S,
+    F64ConvertI64U,
+    F64PromoteF32,
+    I32ReinterpretF32,
+    I64ReinterpretF64,
+    F32ReinterpretI32,
+    F64ReinterpretI64,
+    I32Extend8S,
+    I32Extend16S,
+    I64Extend8S,
+    I64Extend16S,
+    I64Extend32S,
+    I32TruncSatF32S,
+    I32TruncSatF32U,
+    I32TruncSatF64S,
+    I32TruncSatF64U,
+    I64TruncSatF32S,
+    I64TruncSatF32U,
+    I64TruncSatF64S,
+    I64TruncSatF64U,
+
+    // Reference types instructions.
+    TypedSelect(ValType),
+    RefNull(HeapType),
+    RefIsNull,
+    RefFunc(u32),
+    RefAsNonNull,
+
+    // Bulk memory instructions.
+    TableInit { elem_index: u32, table: u32 },
+    ElemDrop(u32),
+    TableFill(u32),
+    TableSet(u32),
+    TableGet(u32),
+    TableGrow(u32),
+    TableSize(u32),
+    TableCopy { src_table: u32, dst_table: u32 },
+
+    // SIMD instructions.
+    V128Load(MemArg),
+    V128Load8x8S(MemArg),
+    V128Load8x8U(MemArg),
+    V128Load16x4S(MemArg),
+    V128Load16x4U(MemArg),
+    V128Load32x2S(MemArg),
+    V128Load32x2U(MemArg),
+    V128Load8Splat(MemArg),
+    V128Load16Splat(MemArg),
+    V128Load32Splat(MemArg),
+    V128Load64Splat(MemArg),
+    V128Load32Zero(MemArg),
+    V128Load64Zero(MemArg),
+    V128Store(MemArg),
+    V128Load8Lane { memarg: MemArg, lane: Lane },
+    V128Load16Lane { memarg: MemArg, lane: Lane },
+    V128Load32Lane { memarg: MemArg, lane: Lane },
+    V128Load64Lane { memarg: MemArg, lane: Lane },
+    V128Store8Lane { memarg: MemArg, lane: Lane },
+    V128Store16Lane { memarg: MemArg, lane: Lane },
+    V128Store32Lane { memarg: MemArg, lane: Lane },
+    V128Store64Lane { memarg: MemArg, lane: Lane },
+    V128Const(i128),
+    I8x16Shuffle([Lane; 16]),
+    I8x16ExtractLaneS(Lane),
+    I8x16ExtractLaneU(Lane),
+    I8x16ReplaceLane(Lane),
+    I16x8ExtractLaneS(Lane),
+    I16x8ExtractLaneU(Lane),
+    I16x8ReplaceLane(Lane),
+    I32x4ExtractLane(Lane),
+    I32x4ReplaceLane(Lane),
+    I64x2ExtractLane(Lane),
+    I64x2ReplaceLane(Lane),
+    F32x4ExtractLane(Lane),
+    F32x4ReplaceLane(Lane),
+    F64x2ExtractLane(Lane),
+    F64x2ReplaceLane(Lane),
+    I8x16Swizzle,
+    I8x16Splat,
+    I16x8Splat,
+    I32x4Splat,
+    I64x2Splat,
+    F32x4Splat,
+    F64x2Splat,
+    I8x16Eq,
+    I8x16Ne,
+    I8x16LtS,
+    I8x16LtU,
+    I8x16GtS,
+    I8x16GtU,
+    I8x16LeS,
+    I8x16LeU,
+    I8x16GeS,
+    I8x16GeU,
+    I16x8Eq,
+    I16x8Ne,
+    I16x8LtS,
+    I16x8LtU,
+    I16x8GtS,
+    I16x8GtU,
+    I16x8LeS,
+    I16x8LeU,
+    I16x8GeS,
+    I16x8GeU,
+    I32x4Eq,
+    I32x4Ne,
+    I32x4LtS,
+    I32x4LtU,
+    I32x4GtS,
+    I32x4GtU,
+    I32x4LeS,
+    I32x4LeU,
+    I32x4GeS,
+    I32x4GeU,
+    I64x2Eq,
+    I64x2Ne,
+    I64x2LtS,
+    I64x2GtS,
+    I64x2LeS,
+    I64x2GeS,
+    F32x4Eq,
+    F32x4Ne,
+    F32x4Lt,
+    F32x4Gt,
+    F32x4Le,
+    F32x4Ge,
+    F64x2Eq,
+    F64x2Ne,
+    F64x2Lt,
+    F64x2Gt,
+    F64x2Le,
+    F64x2Ge,
+    V128Not,
+    V128And,
+    V128AndNot,
+    V128Or,
+    V128Xor,
+    V128Bitselect,
+    V128AnyTrue,
+    I8x16Abs,
+    I8x16Neg,
+    I8x16Popcnt,
+    I8x16AllTrue,
+    I8x16Bitmask,
+    I8x16NarrowI16x8S,
+    I8x16NarrowI16x8U,
+    I8x16Shl,
+    I8x16ShrS,
+    I8x16ShrU,
+    I8x16Add,
+    I8x16AddSatS,
+    I8x16AddSatU,
+    I8x16Sub,
+    I8x16SubSatS,
+    I8x16SubSatU,
+    I8x16MinS,
+    I8x16MinU,
+    I8x16MaxS,
+    I8x16MaxU,
+    I8x16AvgrU,
+    I16x8ExtAddPairwiseI8x16S,
+    I16x8ExtAddPairwiseI8x16U,
+    I16x8Abs,
+    I16x8Neg,
+    I16x8Q15MulrSatS,
+    I16x8AllTrue,
+    I16x8Bitmask,
+    I16x8NarrowI32x4S,
+    I16x8NarrowI32x4U,
+    I16x8ExtendLowI8x16S,
+    I16x8ExtendHighI8x16S,
+    I16x8ExtendLowI8x16U,
+    I16x8ExtendHighI8x16U,
+    I16x8Shl,
+    I16x8ShrS,
+    I16x8ShrU,
+    I16x8Add,
+    I16x8AddSatS,
+    I16x8AddSatU,
+    I16x8Sub,
+    I16x8SubSatS,
+    I16x8SubSatU,
+    I16x8Mul,
+    I16x8MinS,
+    I16x8MinU,
+    I16x8MaxS,
+    I16x8MaxU,
+    I16x8AvgrU,
+    I16x8ExtMulLowI8x16S,
+    I16x8ExtMulHighI8x16S,
+    I16x8ExtMulLowI8x16U,
+    I16x8ExtMulHighI8x16U,
+    I32x4ExtAddPairwiseI16x8S,
+    I32x4ExtAddPairwiseI16x8U,
+    I32x4Abs,
+    I32x4Neg,
+    I32x4AllTrue,
+    I32x4Bitmask,
+    I32x4ExtendLowI16x8S,
+    I32x4ExtendHighI16x8S,
+    I32x4ExtendLowI16x8U,
+    I32x4ExtendHighI16x8U,
+    I32x4Shl,
+    I32x4ShrS,
+    I32x4ShrU,
+    I32x4Add,
+    I32x4Sub,
+    I32x4Mul,
+    I32x4MinS,
+    I32x4MinU,
+    I32x4MaxS,
+    I32x4MaxU,
+    I32x4DotI16x8S,
+    I32x4ExtMulLowI16x8S,
+    I32x4ExtMulHighI16x8S,
+    I32x4ExtMulLowI16x8U,
+    I32x4ExtMulHighI16x8U,
+    I64x2Abs,
+    I64x2Neg,
+    I64x2AllTrue,
+    I64x2Bitmask,
+    I64x2ExtendLowI32x4S,
+    I64x2ExtendHighI32x4S,
+    I64x2ExtendLowI32x4U,
+    I64x2ExtendHighI32x4U,
+    I64x2Shl,
+    I64x2ShrS,
+    I64x2ShrU,
+    I64x2Add,
+    I64x2Sub,
+    I64x2Mul,
+    I64x2ExtMulLowI32x4S,
+    I64x2ExtMulHighI32x4S,
+    I64x2ExtMulLowI32x4U,
+    I64x2ExtMulHighI32x4U,
+    F32x4Ceil,
+    F32x4Floor,
+    F32x4Trunc,
+    F32x4Nearest,
+    F32x4Abs,
+    F32x4Neg,
+    F32x4Sqrt,
+    F32x4Add,
+    F32x4Sub,
+    F32x4Mul,
+    F32x4Div,
+    F32x4Min,
+    F32x4Max,
+    F32x4PMin,
+    F32x4PMax,
+    F64x2Ceil,
+    F64x2Floor,
+    F64x2Trunc,
+    F64x2Nearest,
+    F64x2Abs,
+    F64x2Neg,
+    F64x2Sqrt,
+    F64x2Add,
+    F64x2Sub,
+    F64x2Mul,
+    F64x2Div,
+    F64x2Min,
+    F64x2Max,
+    F64x2PMin,
+    F64x2PMax,
+    I32x4TruncSatF32x4S,
+    I32x4TruncSatF32x4U,
+    F32x4ConvertI32x4S,
+    F32x4ConvertI32x4U,
+    I32x4TruncSatF64x2SZero,
+    I32x4TruncSatF64x2UZero,
+    F64x2ConvertLowI32x4S,
+    F64x2ConvertLowI32x4U,
+    F32x4DemoteF64x2Zero,
+    F64x2PromoteLowF32x4,
+
+    // Relaxed simd proposal
+    I8x16RelaxedSwizzle,
+    I32x4RelaxedTruncF32x4S,
+    I32x4RelaxedTruncF32x4U,
+    I32x4RelaxedTruncF64x2SZero,
+    I32x4RelaxedTruncF64x2UZero,
+    F32x4RelaxedMadd,
+    F32x4RelaxedNmadd,
+    F64x2RelaxedMadd,
+    F64x2RelaxedNmadd,
+    I8x16RelaxedLaneselect,
+    I16x8RelaxedLaneselect,
+    I32x4RelaxedLaneselect,
+    I64x2RelaxedLaneselect,
+    F32x4RelaxedMin,
+    F32x4RelaxedMax,
+    F64x2RelaxedMin,
+    F64x2RelaxedMax,
+    I16x8RelaxedQ15mulrS,
+    I16x8RelaxedDotI8x16I7x16S,
+    I32x4RelaxedDotI8x16I7x16AddS,
+
+    // Atomic instructions (the threads proposal)
+    MemoryAtomicNotify(MemArg),
+    MemoryAtomicWait32(MemArg),
+    MemoryAtomicWait64(MemArg),
+    AtomicFence,
+    I32AtomicLoad(MemArg),
+    I64AtomicLoad(MemArg),
+    I32AtomicLoad8U(MemArg),
+    I32AtomicLoad16U(MemArg),
+    I64AtomicLoad8U(MemArg),
+    I64AtomicLoad16U(MemArg),
+    I64AtomicLoad32U(MemArg),
+    I32AtomicStore(MemArg),
+    I64AtomicStore(MemArg),
+    I32AtomicStore8(MemArg),
+    I32AtomicStore16(MemArg),
+    I64AtomicStore8(MemArg),
+    I64AtomicStore16(MemArg),
+    I64AtomicStore32(MemArg),
+    I32AtomicRmwAdd(MemArg),
+    I64AtomicRmwAdd(MemArg),
+    I32AtomicRmw8AddU(MemArg),
+    I32AtomicRmw16AddU(MemArg),
+    I64AtomicRmw8AddU(MemArg),
+    I64AtomicRmw16AddU(MemArg),
+    I64AtomicRmw32AddU(MemArg),
+    I32AtomicRmwSub(MemArg),
+    I64AtomicRmwSub(MemArg),
+    I32AtomicRmw8SubU(MemArg),
+    I32AtomicRmw16SubU(MemArg),
+    I64AtomicRmw8SubU(MemArg),
+    I64AtomicRmw16SubU(MemArg),
+    I64AtomicRmw32SubU(MemArg),
+    I32AtomicRmwAnd(MemArg),
+    I64AtomicRmwAnd(MemArg),
+    I32AtomicRmw8AndU(MemArg),
+    I32AtomicRmw16AndU(MemArg),
+    I64AtomicRmw8AndU(MemArg),
+    I64AtomicRmw16AndU(MemArg),
+    I64AtomicRmw32AndU(MemArg),
+    I32AtomicRmwOr(MemArg),
+    I64AtomicRmwOr(MemArg),
+    I32AtomicRmw8OrU(MemArg),
+    I32AtomicRmw16OrU(MemArg),
+    I64AtomicRmw8OrU(MemArg),
+    I64AtomicRmw16OrU(MemArg),
+    I64AtomicRmw32OrU(MemArg),
+    I32AtomicRmwXor(MemArg),
+    I64AtomicRmwXor(MemArg),
+    I32AtomicRmw8XorU(MemArg),
+    I32AtomicRmw16XorU(MemArg),
+    I64AtomicRmw8XorU(MemArg),
+    I64AtomicRmw16XorU(MemArg),
+    I64AtomicRmw32XorU(MemArg),
+    I32AtomicRmwXchg(MemArg),
+    I64AtomicRmwXchg(MemArg),
+    I32AtomicRmw8XchgU(MemArg),
+    I32AtomicRmw16XchgU(MemArg),
+    I64AtomicRmw8XchgU(MemArg),
+    I64AtomicRmw16XchgU(MemArg),
+    I64AtomicRmw32XchgU(MemArg),
+    I32AtomicRmwCmpxchg(MemArg),
+    I64AtomicRmwCmpxchg(MemArg),
+    I32AtomicRmw8CmpxchgU(MemArg),
+    I32AtomicRmw16CmpxchgU(MemArg),
+    I64AtomicRmw8CmpxchgU(MemArg),
+    I64AtomicRmw16CmpxchgU(MemArg),
+    I64AtomicRmw32CmpxchgU(MemArg),
+}
+
+impl Encode for Instruction<'_> {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match *self {
+            // Control instructions.
+            Instruction::Unreachable => sink.push(0x00),
+            Instruction::Nop => sink.push(0x01),
+            Instruction::Block(bt) => {
+                sink.push(0x02);
+                bt.encode(sink);
+            }
+            Instruction::Loop(bt) => {
+                sink.push(0x03);
+                bt.encode(sink);
+            }
+            Instruction::If(bt) => {
+                sink.push(0x04);
+                bt.encode(sink);
+            }
+            Instruction::Else => sink.push(0x05),
+            Instruction::Try(bt) => {
+                sink.push(0x06);
+                bt.encode(sink);
+            }
+            Instruction::Catch(t) => {
+                sink.push(0x07);
+                t.encode(sink);
+            }
+            Instruction::Throw(t) => {
+                sink.push(0x08);
+                t.encode(sink);
+            }
+            Instruction::Rethrow(l) => {
+                sink.push(0x09);
+                l.encode(sink);
+            }
+            Instruction::End => sink.push(0x0B),
+            Instruction::Br(l) => {
+                sink.push(0x0C);
+                l.encode(sink);
+            }
+            Instruction::BrIf(l) => {
+                sink.push(0x0D);
+                l.encode(sink);
+            }
+            Instruction::BrTable(ref ls, l) => {
+                sink.push(0x0E);
+                ls.encode(sink);
+                l.encode(sink);
+            }
+            Instruction::BrOnNull(l) => {
+                sink.push(0xD4);
+                l.encode(sink);
+            }
+            Instruction::BrOnNonNull(l) => {
+                sink.push(0xD6);
+                l.encode(sink);
+            }
+            Instruction::Return => sink.push(0x0F),
+            Instruction::Call(f) => {
+                sink.push(0x10);
+                f.encode(sink);
+            }
+            Instruction::CallRef(ty) => {
+                sink.push(0x14);
+                ty.encode(sink);
+            }
+            Instruction::CallIndirect { ty, table } => {
+                sink.push(0x11);
+                ty.encode(sink);
+                table.encode(sink);
+            }
+            Instruction::ReturnCallRef(ty) => {
+                sink.push(0x15);
+                ty.encode(sink);
+            }
+
+            Instruction::ReturnCall(f) => {
+                sink.push(0x12);
+                f.encode(sink);
+            }
+            Instruction::ReturnCallIndirect { ty, table } => {
+                sink.push(0x13);
+                ty.encode(sink);
+                table.encode(sink);
+            }
+            Instruction::Delegate(l) => {
+                sink.push(0x18);
+                l.encode(sink);
+            }
+            Instruction::CatchAll => {
+                sink.push(0x19);
+            }
+
+            // Parametric instructions.
+            Instruction::Drop => sink.push(0x1A),
+            Instruction::Select => sink.push(0x1B),
+            Instruction::TypedSelect(ty) => {
+                sink.push(0x1c);
+                [ty].encode(sink);
+            }
+
+            // Variable instructions.
+            Instruction::LocalGet(l) => {
+                sink.push(0x20);
+                l.encode(sink);
+            }
+            Instruction::LocalSet(l) => {
+                sink.push(0x21);
+                l.encode(sink);
+            }
+            Instruction::LocalTee(l) => {
+                sink.push(0x22);
+                l.encode(sink);
+            }
+            Instruction::GlobalGet(g) => {
+                sink.push(0x23);
+                g.encode(sink);
+            }
+            Instruction::GlobalSet(g) => {
+                sink.push(0x24);
+                g.encode(sink);
+            }
+            Instruction::TableGet(table) => {
+                sink.push(0x25);
+                table.encode(sink);
+            }
+            Instruction::TableSet(table) => {
+                sink.push(0x26);
+                table.encode(sink);
+            }
+
+            // Memory instructions.
+            Instruction::I32Load(m) => {
+                sink.push(0x28);
+                m.encode(sink);
+            }
+            Instruction::I64Load(m) => {
+                sink.push(0x29);
+                m.encode(sink);
+            }
+            Instruction::F32Load(m) => {
+                sink.push(0x2A);
+                m.encode(sink);
+            }
+            Instruction::F64Load(m) => {
+                sink.push(0x2B);
+                m.encode(sink);
+            }
+            Instruction::I32Load8S(m) => {
+                sink.push(0x2C);
+                m.encode(sink);
+            }
+            Instruction::I32Load8U(m) => {
+                sink.push(0x2D);
+                m.encode(sink);
+            }
+            Instruction::I32Load16S(m) => {
+                sink.push(0x2E);
+                m.encode(sink);
+            }
+            Instruction::I32Load16U(m) => {
+                sink.push(0x2F);
+                m.encode(sink);
+            }
+            Instruction::I64Load8S(m) => {
+                sink.push(0x30);
+                m.encode(sink);
+            }
+            Instruction::I64Load8U(m) => {
+                sink.push(0x31);
+                m.encode(sink);
+            }
+            Instruction::I64Load16S(m) => {
+                sink.push(0x32);
+                m.encode(sink);
+            }
+            Instruction::I64Load16U(m) => {
+                sink.push(0x33);
+                m.encode(sink);
+            }
+            Instruction::I64Load32S(m) => {
+                sink.push(0x34);
+                m.encode(sink);
+            }
+            Instruction::I64Load32U(m) => {
+                sink.push(0x35);
+                m.encode(sink);
+            }
+            Instruction::I32Store(m) => {
+                sink.push(0x36);
+                m.encode(sink);
+            }
+            Instruction::I64Store(m) => {
+                sink.push(0x37);
+                m.encode(sink);
+            }
+            Instruction::F32Store(m) => {
+                sink.push(0x38);
+                m.encode(sink);
+            }
+            Instruction::F64Store(m) => {
+                sink.push(0x39);
+                m.encode(sink);
+            }
+            Instruction::I32Store8(m) => {
+                sink.push(0x3A);
+                m.encode(sink);
+            }
+            Instruction::I32Store16(m) => {
+                sink.push(0x3B);
+                m.encode(sink);
+            }
+            Instruction::I64Store8(m) => {
+                sink.push(0x3C);
+                m.encode(sink);
+            }
+            Instruction::I64Store16(m) => {
+                sink.push(0x3D);
+                m.encode(sink);
+            }
+            Instruction::I64Store32(m) => {
+                sink.push(0x3E);
+                m.encode(sink);
+            }
+            Instruction::MemorySize(i) => {
+                sink.push(0x3F);
+                i.encode(sink);
+            }
+            Instruction::MemoryGrow(i) => {
+                sink.push(0x40);
+                i.encode(sink);
+            }
+            Instruction::MemoryInit { mem, data_index } => {
+                sink.push(0xfc);
+                sink.push(0x08);
+                data_index.encode(sink);
+                mem.encode(sink);
+            }
+            Instruction::DataDrop(data) => {
+                sink.push(0xfc);
+                sink.push(0x09);
+                data.encode(sink);
+            }
+            Instruction::MemoryCopy { src_mem, dst_mem } => {
+                sink.push(0xfc);
+                sink.push(0x0a);
+                dst_mem.encode(sink);
+                src_mem.encode(sink);
+            }
+            Instruction::MemoryFill(mem) => {
+                sink.push(0xfc);
+                sink.push(0x0b);
+                mem.encode(sink);
+            }
+            Instruction::MemoryDiscard(mem) => {
+                sink.push(0xfc);
+                sink.push(0x12);
+                mem.encode(sink);
+            }
+
+            // Numeric instructions.
+            Instruction::I32Const(x) => {
+                sink.push(0x41);
+                x.encode(sink);
+            }
+            Instruction::I64Const(x) => {
+                sink.push(0x42);
+                x.encode(sink);
+            }
+            Instruction::F32Const(x) => {
+                sink.push(0x43);
+                let x = x.to_bits();
+                sink.extend(x.to_le_bytes().iter().copied());
+            }
+            Instruction::F64Const(x) => {
+                sink.push(0x44);
+                let x = x.to_bits();
+                sink.extend(x.to_le_bytes().iter().copied());
+            }
+            Instruction::I32Eqz => sink.push(0x45),
+            Instruction::I32Eq => sink.push(0x46),
+            Instruction::I32Ne => sink.push(0x47),
+            Instruction::I32LtS => sink.push(0x48),
+            Instruction::I32LtU => sink.push(0x49),
+            Instruction::I32GtS => sink.push(0x4A),
+            Instruction::I32GtU => sink.push(0x4B),
+            Instruction::I32LeS => sink.push(0x4C),
+            Instruction::I32LeU => sink.push(0x4D),
+            Instruction::I32GeS => sink.push(0x4E),
+            Instruction::I32GeU => sink.push(0x4F),
+            Instruction::I64Eqz => sink.push(0x50),
+            Instruction::I64Eq => sink.push(0x51),
+            Instruction::I64Ne => sink.push(0x52),
+            Instruction::I64LtS => sink.push(0x53),
+            Instruction::I64LtU => sink.push(0x54),
+            Instruction::I64GtS => sink.push(0x55),
+            Instruction::I64GtU => sink.push(0x56),
+            Instruction::I64LeS => sink.push(0x57),
+            Instruction::I64LeU => sink.push(0x58),
+            Instruction::I64GeS => sink.push(0x59),
+            Instruction::I64GeU => sink.push(0x5A),
+            Instruction::F32Eq => sink.push(0x5B),
+            Instruction::F32Ne => sink.push(0x5C),
+            Instruction::F32Lt => sink.push(0x5D),
+            Instruction::F32Gt => sink.push(0x5E),
+            Instruction::F32Le => sink.push(0x5F),
+            Instruction::F32Ge => sink.push(0x60),
+            Instruction::F64Eq => sink.push(0x61),
+            Instruction::F64Ne => sink.push(0x62),
+            Instruction::F64Lt => sink.push(0x63),
+            Instruction::F64Gt => sink.push(0x64),
+            Instruction::F64Le => sink.push(0x65),
+            Instruction::F64Ge => sink.push(0x66),
+            Instruction::I32Clz => sink.push(0x67),
+            Instruction::I32Ctz => sink.push(0x68),
+            Instruction::I32Popcnt => sink.push(0x69),
+            Instruction::I32Add => sink.push(0x6A),
+            Instruction::I32Sub => sink.push(0x6B),
+            Instruction::I32Mul => sink.push(0x6C),
+            Instruction::I32DivS => sink.push(0x6D),
+            Instruction::I32DivU => sink.push(0x6E),
+            Instruction::I32RemS => sink.push(0x6F),
+            Instruction::I32RemU => sink.push(0x70),
+            Instruction::I32And => sink.push(0x71),
+            Instruction::I32Or => sink.push(0x72),
+            Instruction::I32Xor => sink.push(0x73),
+            Instruction::I32Shl => sink.push(0x74),
+            Instruction::I32ShrS => sink.push(0x75),
+            Instruction::I32ShrU => sink.push(0x76),
+            Instruction::I32Rotl => sink.push(0x77),
+            Instruction::I32Rotr => sink.push(0x78),
+            Instruction::I64Clz => sink.push(0x79),
+            Instruction::I64Ctz => sink.push(0x7A),
+            Instruction::I64Popcnt => sink.push(0x7B),
+            Instruction::I64Add => sink.push(0x7C),
+            Instruction::I64Sub => sink.push(0x7D),
+            Instruction::I64Mul => sink.push(0x7E),
+            Instruction::I64DivS => sink.push(0x7F),
+            Instruction::I64DivU => sink.push(0x80),
+            Instruction::I64RemS => sink.push(0x81),
+            Instruction::I64RemU => sink.push(0x82),
+            Instruction::I64And => sink.push(0x83),
+            Instruction::I64Or => sink.push(0x84),
+            Instruction::I64Xor => sink.push(0x85),
+            Instruction::I64Shl => sink.push(0x86),
+            Instruction::I64ShrS => sink.push(0x87),
+            Instruction::I64ShrU => sink.push(0x88),
+            Instruction::I64Rotl => sink.push(0x89),
+            Instruction::I64Rotr => sink.push(0x8A),
+            Instruction::F32Abs => sink.push(0x8B),
+            Instruction::F32Neg => sink.push(0x8C),
+            Instruction::F32Ceil => sink.push(0x8D),
+            Instruction::F32Floor => sink.push(0x8E),
+            Instruction::F32Trunc => sink.push(0x8F),
+            Instruction::F32Nearest => sink.push(0x90),
+            Instruction::F32Sqrt => sink.push(0x91),
+            Instruction::F32Add => sink.push(0x92),
+            Instruction::F32Sub => sink.push(0x93),
+            Instruction::F32Mul => sink.push(0x94),
+            Instruction::F32Div => sink.push(0x95),
+            Instruction::F32Min => sink.push(0x96),
+            Instruction::F32Max => sink.push(0x97),
+            Instruction::F32Copysign => sink.push(0x98),
+            Instruction::F64Abs => sink.push(0x99),
+            Instruction::F64Neg => sink.push(0x9A),
+            Instruction::F64Ceil => sink.push(0x9B),
+            Instruction::F64Floor => sink.push(0x9C),
+            Instruction::F64Trunc => sink.push(0x9D),
+            Instruction::F64Nearest => sink.push(0x9E),
+            Instruction::F64Sqrt => sink.push(0x9F),
+            Instruction::F64Add => sink.push(0xA0),
+            Instruction::F64Sub => sink.push(0xA1),
+            Instruction::F64Mul => sink.push(0xA2),
+            Instruction::F64Div => sink.push(0xA3),
+            Instruction::F64Min => sink.push(0xA4),
+            Instruction::F64Max => sink.push(0xA5),
+            Instruction::F64Copysign => sink.push(0xA6),
+            Instruction::I32WrapI64 => sink.push(0xA7),
+            Instruction::I32TruncF32S => sink.push(0xA8),
+            Instruction::I32TruncF32U => sink.push(0xA9),
+            Instruction::I32TruncF64S => sink.push(0xAA),
+            Instruction::I32TruncF64U => sink.push(0xAB),
+            Instruction::I64ExtendI32S => sink.push(0xAC),
+            Instruction::I64ExtendI32U => sink.push(0xAD),
+            Instruction::I64TruncF32S => sink.push(0xAE),
+            Instruction::I64TruncF32U => sink.push(0xAF),
+            Instruction::I64TruncF64S => sink.push(0xB0),
+            Instruction::I64TruncF64U => sink.push(0xB1),
+            Instruction::F32ConvertI32S => sink.push(0xB2),
+            Instruction::F32ConvertI32U => sink.push(0xB3),
+            Instruction::F32ConvertI64S => sink.push(0xB4),
+            Instruction::F32ConvertI64U => sink.push(0xB5),
+            Instruction::F32DemoteF64 => sink.push(0xB6),
+            Instruction::F64ConvertI32S => sink.push(0xB7),
+            Instruction::F64ConvertI32U => sink.push(0xB8),
+            Instruction::F64ConvertI64S => sink.push(0xB9),
+            Instruction::F64ConvertI64U => sink.push(0xBA),
+            Instruction::F64PromoteF32 => sink.push(0xBB),
+            Instruction::I32ReinterpretF32 => sink.push(0xBC),
+            Instruction::I64ReinterpretF64 => sink.push(0xBD),
+            Instruction::F32ReinterpretI32 => sink.push(0xBE),
+            Instruction::F64ReinterpretI64 => sink.push(0xBF),
+            Instruction::I32Extend8S => sink.push(0xC0),
+            Instruction::I32Extend16S => sink.push(0xC1),
+            Instruction::I64Extend8S => sink.push(0xC2),
+            Instruction::I64Extend16S => sink.push(0xC3),
+            Instruction::I64Extend32S => sink.push(0xC4),
+
+            Instruction::I32TruncSatF32S => {
+                sink.push(0xFC);
+                sink.push(0x00);
+            }
+            Instruction::I32TruncSatF32U => {
+                sink.push(0xFC);
+                sink.push(0x01);
+            }
+            Instruction::I32TruncSatF64S => {
+                sink.push(0xFC);
+                sink.push(0x02);
+            }
+            Instruction::I32TruncSatF64U => {
+                sink.push(0xFC);
+                sink.push(0x03);
+            }
+            Instruction::I64TruncSatF32S => {
+                sink.push(0xFC);
+                sink.push(0x04);
+            }
+            Instruction::I64TruncSatF32U => {
+                sink.push(0xFC);
+                sink.push(0x05);
+            }
+            Instruction::I64TruncSatF64S => {
+                sink.push(0xFC);
+                sink.push(0x06);
+            }
+            Instruction::I64TruncSatF64U => {
+                sink.push(0xFC);
+                sink.push(0x07);
+            }
+
+            // Reference types instructions.
+            Instruction::RefNull(ty) => {
+                sink.push(0xd0);
+                ty.encode(sink);
+            }
+            Instruction::RefIsNull => sink.push(0xd1),
+            Instruction::RefFunc(f) => {
+                sink.push(0xd2);
+                f.encode(sink);
+            }
+            Instruction::RefAsNonNull => sink.push(0xD3),
+
+            // Bulk memory instructions.
+            Instruction::TableInit { elem_index, table } => {
+                sink.push(0xfc);
+                sink.push(0x0c);
+                elem_index.encode(sink);
+                table.encode(sink);
+            }
+            Instruction::ElemDrop(segment) => {
+                sink.push(0xfc);
+                sink.push(0x0d);
+                segment.encode(sink);
+            }
+            Instruction::TableCopy {
+                src_table,
+                dst_table,
+            } => {
+                sink.push(0xfc);
+                sink.push(0x0e);
+                dst_table.encode(sink);
+                src_table.encode(sink);
+            }
+            Instruction::TableGrow(table) => {
+                sink.push(0xfc);
+                sink.push(0x0f);
+                table.encode(sink);
+            }
+            Instruction::TableSize(table) => {
+                sink.push(0xfc);
+                sink.push(0x10);
+                table.encode(sink);
+            }
+            Instruction::TableFill(table) => {
+                sink.push(0xfc);
+                sink.push(0x11);
+                table.encode(sink);
+            }
+
+            // SIMD instructions.
+            Instruction::V128Load(memarg) => {
+                sink.push(0xFD);
+                0x00u32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Load8x8S(memarg) => {
+                sink.push(0xFD);
+                0x01u32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Load8x8U(memarg) => {
+                sink.push(0xFD);
+                0x02u32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Load16x4S(memarg) => {
+                sink.push(0xFD);
+                0x03u32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Load16x4U(memarg) => {
+                sink.push(0xFD);
+                0x04u32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Load32x2S(memarg) => {
+                sink.push(0xFD);
+                0x05u32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Load32x2U(memarg) => {
+                sink.push(0xFD);
+                0x06u32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Load8Splat(memarg) => {
+                sink.push(0xFD);
+                0x07u32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Load16Splat(memarg) => {
+                sink.push(0xFD);
+                0x08u32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Load32Splat(memarg) => {
+                sink.push(0xFD);
+                0x09u32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Load64Splat(memarg) => {
+                sink.push(0xFD);
+                0x0Au32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Store(memarg) => {
+                sink.push(0xFD);
+                0x0Bu32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Const(x) => {
+                sink.push(0xFD);
+                0x0Cu32.encode(sink);
+                sink.extend(x.to_le_bytes().iter().copied());
+            }
+            Instruction::I8x16Shuffle(lanes) => {
+                sink.push(0xFD);
+                0x0Du32.encode(sink);
+                assert!(lanes.iter().all(|l: &u8| *l < 32));
+                sink.extend(lanes.iter().copied());
+            }
+            Instruction::I8x16Swizzle => {
+                sink.push(0xFD);
+                0x0Eu32.encode(sink);
+            }
+            Instruction::I8x16Splat => {
+                sink.push(0xFD);
+                0x0Fu32.encode(sink);
+            }
+            Instruction::I16x8Splat => {
+                sink.push(0xFD);
+                0x10u32.encode(sink);
+            }
+            Instruction::I32x4Splat => {
+                sink.push(0xFD);
+                0x11u32.encode(sink);
+            }
+            Instruction::I64x2Splat => {
+                sink.push(0xFD);
+                0x12u32.encode(sink);
+            }
+            Instruction::F32x4Splat => {
+                sink.push(0xFD);
+                0x13u32.encode(sink);
+            }
+            Instruction::F64x2Splat => {
+                sink.push(0xFD);
+                0x14u32.encode(sink);
+            }
+            Instruction::I8x16ExtractLaneS(lane) => {
+                sink.push(0xFD);
+                0x15u32.encode(sink);
+                assert!(lane < 16);
+                sink.push(lane);
+            }
+            Instruction::I8x16ExtractLaneU(lane) => {
+                sink.push(0xFD);
+                0x16u32.encode(sink);
+                assert!(lane < 16);
+                sink.push(lane);
+            }
+            Instruction::I8x16ReplaceLane(lane) => {
+                sink.push(0xFD);
+                0x17u32.encode(sink);
+                assert!(lane < 16);
+                sink.push(lane);
+            }
+            Instruction::I16x8ExtractLaneS(lane) => {
+                sink.push(0xFD);
+                0x18u32.encode(sink);
+                assert!(lane < 8);
+                sink.push(lane);
+            }
+            Instruction::I16x8ExtractLaneU(lane) => {
+                sink.push(0xFD);
+                0x19u32.encode(sink);
+                assert!(lane < 8);
+                sink.push(lane);
+            }
+            Instruction::I16x8ReplaceLane(lane) => {
+                sink.push(0xFD);
+                0x1Au32.encode(sink);
+                assert!(lane < 8);
+                sink.push(lane);
+            }
+            Instruction::I32x4ExtractLane(lane) => {
+                sink.push(0xFD);
+                0x1Bu32.encode(sink);
+                assert!(lane < 4);
+                sink.push(lane);
+            }
+            Instruction::I32x4ReplaceLane(lane) => {
+                sink.push(0xFD);
+                0x1Cu32.encode(sink);
+                assert!(lane < 4);
+                sink.push(lane);
+            }
+            Instruction::I64x2ExtractLane(lane) => {
+                sink.push(0xFD);
+                0x1Du32.encode(sink);
+                assert!(lane < 2);
+                sink.push(lane);
+            }
+            Instruction::I64x2ReplaceLane(lane) => {
+                sink.push(0xFD);
+                0x1Eu32.encode(sink);
+                assert!(lane < 2);
+                sink.push(lane);
+            }
+            Instruction::F32x4ExtractLane(lane) => {
+                sink.push(0xFD);
+                0x1Fu32.encode(sink);
+                assert!(lane < 4);
+                sink.push(lane);
+            }
+            Instruction::F32x4ReplaceLane(lane) => {
+                sink.push(0xFD);
+                0x20u32.encode(sink);
+                assert!(lane < 4);
+                sink.push(lane);
+            }
+            Instruction::F64x2ExtractLane(lane) => {
+                sink.push(0xFD);
+                0x21u32.encode(sink);
+                assert!(lane < 2);
+                sink.push(lane);
+            }
+            Instruction::F64x2ReplaceLane(lane) => {
+                sink.push(0xFD);
+                0x22u32.encode(sink);
+                assert!(lane < 2);
+                sink.push(lane);
+            }
+
+            Instruction::I8x16Eq => {
+                sink.push(0xFD);
+                0x23u32.encode(sink);
+            }
+            Instruction::I8x16Ne => {
+                sink.push(0xFD);
+                0x24u32.encode(sink);
+            }
+            Instruction::I8x16LtS => {
+                sink.push(0xFD);
+                0x25u32.encode(sink);
+            }
+            Instruction::I8x16LtU => {
+                sink.push(0xFD);
+                0x26u32.encode(sink);
+            }
+            Instruction::I8x16GtS => {
+                sink.push(0xFD);
+                0x27u32.encode(sink);
+            }
+            Instruction::I8x16GtU => {
+                sink.push(0xFD);
+                0x28u32.encode(sink);
+            }
+            Instruction::I8x16LeS => {
+                sink.push(0xFD);
+                0x29u32.encode(sink);
+            }
+            Instruction::I8x16LeU => {
+                sink.push(0xFD);
+                0x2Au32.encode(sink);
+            }
+            Instruction::I8x16GeS => {
+                sink.push(0xFD);
+                0x2Bu32.encode(sink);
+            }
+            Instruction::I8x16GeU => {
+                sink.push(0xFD);
+                0x2Cu32.encode(sink);
+            }
+            Instruction::I16x8Eq => {
+                sink.push(0xFD);
+                0x2Du32.encode(sink);
+            }
+            Instruction::I16x8Ne => {
+                sink.push(0xFD);
+                0x2Eu32.encode(sink);
+            }
+            Instruction::I16x8LtS => {
+                sink.push(0xFD);
+                0x2Fu32.encode(sink);
+            }
+            Instruction::I16x8LtU => {
+                sink.push(0xFD);
+                0x30u32.encode(sink);
+            }
+            Instruction::I16x8GtS => {
+                sink.push(0xFD);
+                0x31u32.encode(sink);
+            }
+            Instruction::I16x8GtU => {
+                sink.push(0xFD);
+                0x32u32.encode(sink);
+            }
+            Instruction::I16x8LeS => {
+                sink.push(0xFD);
+                0x33u32.encode(sink);
+            }
+            Instruction::I16x8LeU => {
+                sink.push(0xFD);
+                0x34u32.encode(sink);
+            }
+            Instruction::I16x8GeS => {
+                sink.push(0xFD);
+                0x35u32.encode(sink);
+            }
+            Instruction::I16x8GeU => {
+                sink.push(0xFD);
+                0x36u32.encode(sink);
+            }
+            Instruction::I32x4Eq => {
+                sink.push(0xFD);
+                0x37u32.encode(sink);
+            }
+            Instruction::I32x4Ne => {
+                sink.push(0xFD);
+                0x38u32.encode(sink);
+            }
+            Instruction::I32x4LtS => {
+                sink.push(0xFD);
+                0x39u32.encode(sink);
+            }
+            Instruction::I32x4LtU => {
+                sink.push(0xFD);
+                0x3Au32.encode(sink);
+            }
+            Instruction::I32x4GtS => {
+                sink.push(0xFD);
+                0x3Bu32.encode(sink);
+            }
+            Instruction::I32x4GtU => {
+                sink.push(0xFD);
+                0x3Cu32.encode(sink);
+            }
+            Instruction::I32x4LeS => {
+                sink.push(0xFD);
+                0x3Du32.encode(sink);
+            }
+            Instruction::I32x4LeU => {
+                sink.push(0xFD);
+                0x3Eu32.encode(sink);
+            }
+            Instruction::I32x4GeS => {
+                sink.push(0xFD);
+                0x3Fu32.encode(sink);
+            }
+            Instruction::I32x4GeU => {
+                sink.push(0xFD);
+                0x40u32.encode(sink);
+            }
+            Instruction::F32x4Eq => {
+                sink.push(0xFD);
+                0x41u32.encode(sink);
+            }
+            Instruction::F32x4Ne => {
+                sink.push(0xFD);
+                0x42u32.encode(sink);
+            }
+            Instruction::F32x4Lt => {
+                sink.push(0xFD);
+                0x43u32.encode(sink);
+            }
+            Instruction::F32x4Gt => {
+                sink.push(0xFD);
+                0x44u32.encode(sink);
+            }
+            Instruction::F32x4Le => {
+                sink.push(0xFD);
+                0x45u32.encode(sink);
+            }
+            Instruction::F32x4Ge => {
+                sink.push(0xFD);
+                0x46u32.encode(sink);
+            }
+            Instruction::F64x2Eq => {
+                sink.push(0xFD);
+                0x47u32.encode(sink);
+            }
+            Instruction::F64x2Ne => {
+                sink.push(0xFD);
+                0x48u32.encode(sink);
+            }
+            Instruction::F64x2Lt => {
+                sink.push(0xFD);
+                0x49u32.encode(sink);
+            }
+            Instruction::F64x2Gt => {
+                sink.push(0xFD);
+                0x4Au32.encode(sink);
+            }
+            Instruction::F64x2Le => {
+                sink.push(0xFD);
+                0x4Bu32.encode(sink);
+            }
+            Instruction::F64x2Ge => {
+                sink.push(0xFD);
+                0x4Cu32.encode(sink);
+            }
+            Instruction::V128Not => {
+                sink.push(0xFD);
+                0x4Du32.encode(sink);
+            }
+            Instruction::V128And => {
+                sink.push(0xFD);
+                0x4Eu32.encode(sink);
+            }
+            Instruction::V128AndNot => {
+                sink.push(0xFD);
+                0x4Fu32.encode(sink);
+            }
+            Instruction::V128Or => {
+                sink.push(0xFD);
+                0x50u32.encode(sink);
+            }
+            Instruction::V128Xor => {
+                sink.push(0xFD);
+                0x51u32.encode(sink);
+            }
+            Instruction::V128Bitselect => {
+                sink.push(0xFD);
+                0x52u32.encode(sink);
+            }
+            Instruction::V128AnyTrue => {
+                sink.push(0xFD);
+                0x53u32.encode(sink);
+            }
+            Instruction::I8x16Abs => {
+                sink.push(0xFD);
+                0x60u32.encode(sink);
+            }
+            Instruction::I8x16Neg => {
+                sink.push(0xFD);
+                0x61u32.encode(sink);
+            }
+            Instruction::I8x16Popcnt => {
+                sink.push(0xFD);
+                0x62u32.encode(sink);
+            }
+            Instruction::I8x16AllTrue => {
+                sink.push(0xFD);
+                0x63u32.encode(sink);
+            }
+            Instruction::I8x16Bitmask => {
+                sink.push(0xFD);
+                0x64u32.encode(sink);
+            }
+            Instruction::I8x16NarrowI16x8S => {
+                sink.push(0xFD);
+                0x65u32.encode(sink);
+            }
+            Instruction::I8x16NarrowI16x8U => {
+                sink.push(0xFD);
+                0x66u32.encode(sink);
+            }
+            Instruction::I8x16Shl => {
+                sink.push(0xFD);
+                0x6bu32.encode(sink);
+            }
+            Instruction::I8x16ShrS => {
+                sink.push(0xFD);
+                0x6cu32.encode(sink);
+            }
+            Instruction::I8x16ShrU => {
+                sink.push(0xFD);
+                0x6du32.encode(sink);
+            }
+            Instruction::I8x16Add => {
+                sink.push(0xFD);
+                0x6eu32.encode(sink);
+            }
+            Instruction::I8x16AddSatS => {
+                sink.push(0xFD);
+                0x6fu32.encode(sink);
+            }
+            Instruction::I8x16AddSatU => {
+                sink.push(0xFD);
+                0x70u32.encode(sink);
+            }
+            Instruction::I8x16Sub => {
+                sink.push(0xFD);
+                0x71u32.encode(sink);
+            }
+            Instruction::I8x16SubSatS => {
+                sink.push(0xFD);
+                0x72u32.encode(sink);
+            }
+            Instruction::I8x16SubSatU => {
+                sink.push(0xFD);
+                0x73u32.encode(sink);
+            }
+            Instruction::I8x16MinS => {
+                sink.push(0xFD);
+                0x76u32.encode(sink);
+            }
+            Instruction::I8x16MinU => {
+                sink.push(0xFD);
+                0x77u32.encode(sink);
+            }
+            Instruction::I8x16MaxS => {
+                sink.push(0xFD);
+                0x78u32.encode(sink);
+            }
+            Instruction::I8x16MaxU => {
+                sink.push(0xFD);
+                0x79u32.encode(sink);
+            }
+            Instruction::I8x16AvgrU => {
+                sink.push(0xFD);
+                0x7Bu32.encode(sink);
+            }
+            Instruction::I16x8ExtAddPairwiseI8x16S => {
+                sink.push(0xFD);
+                0x7Cu32.encode(sink);
+            }
+            Instruction::I16x8ExtAddPairwiseI8x16U => {
+                sink.push(0xFD);
+                0x7Du32.encode(sink);
+            }
+            Instruction::I32x4ExtAddPairwiseI16x8S => {
+                sink.push(0xFD);
+                0x7Eu32.encode(sink);
+            }
+            Instruction::I32x4ExtAddPairwiseI16x8U => {
+                sink.push(0xFD);
+                0x7Fu32.encode(sink);
+            }
+            Instruction::I16x8Abs => {
+                sink.push(0xFD);
+                0x80u32.encode(sink);
+            }
+            Instruction::I16x8Neg => {
+                sink.push(0xFD);
+                0x81u32.encode(sink);
+            }
+            Instruction::I16x8Q15MulrSatS => {
+                sink.push(0xFD);
+                0x82u32.encode(sink);
+            }
+            Instruction::I16x8AllTrue => {
+                sink.push(0xFD);
+                0x83u32.encode(sink);
+            }
+            Instruction::I16x8Bitmask => {
+                sink.push(0xFD);
+                0x84u32.encode(sink);
+            }
+            Instruction::I16x8NarrowI32x4S => {
+                sink.push(0xFD);
+                0x85u32.encode(sink);
+            }
+            Instruction::I16x8NarrowI32x4U => {
+                sink.push(0xFD);
+                0x86u32.encode(sink);
+            }
+            Instruction::I16x8ExtendLowI8x16S => {
+                sink.push(0xFD);
+                0x87u32.encode(sink);
+            }
+            Instruction::I16x8ExtendHighI8x16S => {
+                sink.push(0xFD);
+                0x88u32.encode(sink);
+            }
+            Instruction::I16x8ExtendLowI8x16U => {
+                sink.push(0xFD);
+                0x89u32.encode(sink);
+            }
+            Instruction::I16x8ExtendHighI8x16U => {
+                sink.push(0xFD);
+                0x8Au32.encode(sink);
+            }
+            Instruction::I16x8Shl => {
+                sink.push(0xFD);
+                0x8Bu32.encode(sink);
+            }
+            Instruction::I16x8ShrS => {
+                sink.push(0xFD);
+                0x8Cu32.encode(sink);
+            }
+            Instruction::I16x8ShrU => {
+                sink.push(0xFD);
+                0x8Du32.encode(sink);
+            }
+            Instruction::I16x8Add => {
+                sink.push(0xFD);
+                0x8Eu32.encode(sink);
+            }
+            Instruction::I16x8AddSatS => {
+                sink.push(0xFD);
+                0x8Fu32.encode(sink);
+            }
+            Instruction::I16x8AddSatU => {
+                sink.push(0xFD);
+                0x90u32.encode(sink);
+            }
+            Instruction::I16x8Sub => {
+                sink.push(0xFD);
+                0x91u32.encode(sink);
+            }
+            Instruction::I16x8SubSatS => {
+                sink.push(0xFD);
+                0x92u32.encode(sink);
+            }
+            Instruction::I16x8SubSatU => {
+                sink.push(0xFD);
+                0x93u32.encode(sink);
+            }
+            Instruction::I16x8Mul => {
+                sink.push(0xFD);
+                0x95u32.encode(sink);
+            }
+            Instruction::I16x8MinS => {
+                sink.push(0xFD);
+                0x96u32.encode(sink);
+            }
+            Instruction::I16x8MinU => {
+                sink.push(0xFD);
+                0x97u32.encode(sink);
+            }
+            Instruction::I16x8MaxS => {
+                sink.push(0xFD);
+                0x98u32.encode(sink);
+            }
+            Instruction::I16x8MaxU => {
+                sink.push(0xFD);
+                0x99u32.encode(sink);
+            }
+            Instruction::I16x8AvgrU => {
+                sink.push(0xFD);
+                0x9Bu32.encode(sink);
+            }
+            Instruction::I16x8ExtMulLowI8x16S => {
+                sink.push(0xFD);
+                0x9Cu32.encode(sink);
+            }
+            Instruction::I16x8ExtMulHighI8x16S => {
+                sink.push(0xFD);
+                0x9Du32.encode(sink);
+            }
+            Instruction::I16x8ExtMulLowI8x16U => {
+                sink.push(0xFD);
+                0x9Eu32.encode(sink);
+            }
+            Instruction::I16x8ExtMulHighI8x16U => {
+                sink.push(0xFD);
+                0x9Fu32.encode(sink);
+            }
+            Instruction::I32x4Abs => {
+                sink.push(0xFD);
+                0xA0u32.encode(sink);
+            }
+            Instruction::I32x4Neg => {
+                sink.push(0xFD);
+                0xA1u32.encode(sink);
+            }
+            Instruction::I32x4AllTrue => {
+                sink.push(0xFD);
+                0xA3u32.encode(sink);
+            }
+            Instruction::I32x4Bitmask => {
+                sink.push(0xFD);
+                0xA4u32.encode(sink);
+            }
+            Instruction::I32x4ExtendLowI16x8S => {
+                sink.push(0xFD);
+                0xA7u32.encode(sink);
+            }
+            Instruction::I32x4ExtendHighI16x8S => {
+                sink.push(0xFD);
+                0xA8u32.encode(sink);
+            }
+            Instruction::I32x4ExtendLowI16x8U => {
+                sink.push(0xFD);
+                0xA9u32.encode(sink);
+            }
+            Instruction::I32x4ExtendHighI16x8U => {
+                sink.push(0xFD);
+                0xAAu32.encode(sink);
+            }
+            Instruction::I32x4Shl => {
+                sink.push(0xFD);
+                0xABu32.encode(sink);
+            }
+            Instruction::I32x4ShrS => {
+                sink.push(0xFD);
+                0xACu32.encode(sink);
+            }
+            Instruction::I32x4ShrU => {
+                sink.push(0xFD);
+                0xADu32.encode(sink);
+            }
+            Instruction::I32x4Add => {
+                sink.push(0xFD);
+                0xAEu32.encode(sink);
+            }
+            Instruction::I32x4Sub => {
+                sink.push(0xFD);
+                0xB1u32.encode(sink);
+            }
+            Instruction::I32x4Mul => {
+                sink.push(0xFD);
+                0xB5u32.encode(sink);
+            }
+            Instruction::I32x4MinS => {
+                sink.push(0xFD);
+                0xB6u32.encode(sink);
+            }
+            Instruction::I32x4MinU => {
+                sink.push(0xFD);
+                0xB7u32.encode(sink);
+            }
+            Instruction::I32x4MaxS => {
+                sink.push(0xFD);
+                0xB8u32.encode(sink);
+            }
+            Instruction::I32x4MaxU => {
+                sink.push(0xFD);
+                0xB9u32.encode(sink);
+            }
+            Instruction::I32x4DotI16x8S => {
+                sink.push(0xFD);
+                0xBAu32.encode(sink);
+            }
+            Instruction::I32x4ExtMulLowI16x8S => {
+                sink.push(0xFD);
+                0xBCu32.encode(sink);
+            }
+            Instruction::I32x4ExtMulHighI16x8S => {
+                sink.push(0xFD);
+                0xBDu32.encode(sink);
+            }
+            Instruction::I32x4ExtMulLowI16x8U => {
+                sink.push(0xFD);
+                0xBEu32.encode(sink);
+            }
+            Instruction::I32x4ExtMulHighI16x8U => {
+                sink.push(0xFD);
+                0xBFu32.encode(sink);
+            }
+            Instruction::I64x2Abs => {
+                sink.push(0xFD);
+                0xC0u32.encode(sink);
+            }
+            Instruction::I64x2Neg => {
+                sink.push(0xFD);
+                0xC1u32.encode(sink);
+            }
+            Instruction::I64x2AllTrue => {
+                sink.push(0xFD);
+                0xC3u32.encode(sink);
+            }
+            Instruction::I64x2Bitmask => {
+                sink.push(0xFD);
+                0xC4u32.encode(sink);
+            }
+            Instruction::I64x2ExtendLowI32x4S => {
+                sink.push(0xFD);
+                0xC7u32.encode(sink);
+            }
+            Instruction::I64x2ExtendHighI32x4S => {
+                sink.push(0xFD);
+                0xC8u32.encode(sink);
+            }
+            Instruction::I64x2ExtendLowI32x4U => {
+                sink.push(0xFD);
+                0xC9u32.encode(sink);
+            }
+            Instruction::I64x2ExtendHighI32x4U => {
+                sink.push(0xFD);
+                0xCAu32.encode(sink);
+            }
+            Instruction::I64x2Shl => {
+                sink.push(0xFD);
+                0xCBu32.encode(sink);
+            }
+            Instruction::I64x2ShrS => {
+                sink.push(0xFD);
+                0xCCu32.encode(sink);
+            }
+            Instruction::I64x2ShrU => {
+                sink.push(0xFD);
+                0xCDu32.encode(sink);
+            }
+            Instruction::I64x2Add => {
+                sink.push(0xFD);
+                0xCEu32.encode(sink);
+            }
+            Instruction::I64x2Sub => {
+                sink.push(0xFD);
+                0xD1u32.encode(sink);
+            }
+            Instruction::I64x2Mul => {
+                sink.push(0xFD);
+                0xD5u32.encode(sink);
+            }
+            Instruction::I64x2ExtMulLowI32x4S => {
+                sink.push(0xFD);
+                0xDCu32.encode(sink);
+            }
+            Instruction::I64x2ExtMulHighI32x4S => {
+                sink.push(0xFD);
+                0xDDu32.encode(sink);
+            }
+            Instruction::I64x2ExtMulLowI32x4U => {
+                sink.push(0xFD);
+                0xDEu32.encode(sink);
+            }
+            Instruction::I64x2ExtMulHighI32x4U => {
+                sink.push(0xFD);
+                0xDFu32.encode(sink);
+            }
+            Instruction::F32x4Ceil => {
+                sink.push(0xFD);
+                0x67u32.encode(sink);
+            }
+            Instruction::F32x4Floor => {
+                sink.push(0xFD);
+                0x68u32.encode(sink);
+            }
+            Instruction::F32x4Trunc => {
+                sink.push(0xFD);
+                0x69u32.encode(sink);
+            }
+            Instruction::F32x4Nearest => {
+                sink.push(0xFD);
+                0x6Au32.encode(sink);
+            }
+            Instruction::F32x4Abs => {
+                sink.push(0xFD);
+                0xE0u32.encode(sink);
+            }
+            Instruction::F32x4Neg => {
+                sink.push(0xFD);
+                0xE1u32.encode(sink);
+            }
+            Instruction::F32x4Sqrt => {
+                sink.push(0xFD);
+                0xE3u32.encode(sink);
+            }
+            Instruction::F32x4Add => {
+                sink.push(0xFD);
+                0xE4u32.encode(sink);
+            }
+            Instruction::F32x4Sub => {
+                sink.push(0xFD);
+                0xE5u32.encode(sink);
+            }
+            Instruction::F32x4Mul => {
+                sink.push(0xFD);
+                0xE6u32.encode(sink);
+            }
+            Instruction::F32x4Div => {
+                sink.push(0xFD);
+                0xE7u32.encode(sink);
+            }
+            Instruction::F32x4Min => {
+                sink.push(0xFD);
+                0xE8u32.encode(sink);
+            }
+            Instruction::F32x4Max => {
+                sink.push(0xFD);
+                0xE9u32.encode(sink);
+            }
+            Instruction::F32x4PMin => {
+                sink.push(0xFD);
+                0xEAu32.encode(sink);
+            }
+            Instruction::F32x4PMax => {
+                sink.push(0xFD);
+                0xEBu32.encode(sink);
+            }
+            Instruction::F64x2Ceil => {
+                sink.push(0xFD);
+                0x74u32.encode(sink);
+            }
+            Instruction::F64x2Floor => {
+                sink.push(0xFD);
+                0x75u32.encode(sink);
+            }
+            Instruction::F64x2Trunc => {
+                sink.push(0xFD);
+                0x7Au32.encode(sink);
+            }
+            Instruction::F64x2Nearest => {
+                sink.push(0xFD);
+                0x94u32.encode(sink);
+            }
+            Instruction::F64x2Abs => {
+                sink.push(0xFD);
+                0xECu32.encode(sink);
+            }
+            Instruction::F64x2Neg => {
+                sink.push(0xFD);
+                0xEDu32.encode(sink);
+            }
+            Instruction::F64x2Sqrt => {
+                sink.push(0xFD);
+                0xEFu32.encode(sink);
+            }
+            Instruction::F64x2Add => {
+                sink.push(0xFD);
+                0xF0u32.encode(sink);
+            }
+            Instruction::F64x2Sub => {
+                sink.push(0xFD);
+                0xF1u32.encode(sink);
+            }
+            Instruction::F64x2Mul => {
+                sink.push(0xFD);
+                0xF2u32.encode(sink);
+            }
+            Instruction::F64x2Div => {
+                sink.push(0xFD);
+                0xF3u32.encode(sink);
+            }
+            Instruction::F64x2Min => {
+                sink.push(0xFD);
+                0xF4u32.encode(sink);
+            }
+            Instruction::F64x2Max => {
+                sink.push(0xFD);
+                0xF5u32.encode(sink);
+            }
+            Instruction::F64x2PMin => {
+                sink.push(0xFD);
+                0xF6u32.encode(sink);
+            }
+            Instruction::F64x2PMax => {
+                sink.push(0xFD);
+                0xF7u32.encode(sink);
+            }
+            Instruction::I32x4TruncSatF32x4S => {
+                sink.push(0xFD);
+                0xF8u32.encode(sink);
+            }
+            Instruction::I32x4TruncSatF32x4U => {
+                sink.push(0xFD);
+                0xF9u32.encode(sink);
+            }
+            Instruction::F32x4ConvertI32x4S => {
+                sink.push(0xFD);
+                0xFAu32.encode(sink);
+            }
+            Instruction::F32x4ConvertI32x4U => {
+                sink.push(0xFD);
+                0xFBu32.encode(sink);
+            }
+            Instruction::I32x4TruncSatF64x2SZero => {
+                sink.push(0xFD);
+                0xFCu32.encode(sink);
+            }
+            Instruction::I32x4TruncSatF64x2UZero => {
+                sink.push(0xFD);
+                0xFDu32.encode(sink);
+            }
+            Instruction::F64x2ConvertLowI32x4S => {
+                sink.push(0xFD);
+                0xFEu32.encode(sink);
+            }
+            Instruction::F64x2ConvertLowI32x4U => {
+                sink.push(0xFD);
+                0xFFu32.encode(sink);
+            }
+            Instruction::F32x4DemoteF64x2Zero => {
+                sink.push(0xFD);
+                0x5Eu32.encode(sink);
+            }
+            Instruction::F64x2PromoteLowF32x4 => {
+                sink.push(0xFD);
+                0x5Fu32.encode(sink);
+            }
+            Instruction::V128Load32Zero(memarg) => {
+                sink.push(0xFD);
+                0x5Cu32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Load64Zero(memarg) => {
+                sink.push(0xFD);
+                0x5Du32.encode(sink);
+                memarg.encode(sink);
+            }
+            Instruction::V128Load8Lane { memarg, lane } => {
+                sink.push(0xFD);
+                0x54u32.encode(sink);
+                memarg.encode(sink);
+                assert!(lane < 16);
+                sink.push(lane);
+            }
+            Instruction::V128Load16Lane { memarg, lane } => {
+                sink.push(0xFD);
+                0x55u32.encode(sink);
+                memarg.encode(sink);
+                assert!(lane < 8);
+                sink.push(lane);
+            }
+            Instruction::V128Load32Lane { memarg, lane } => {
+                sink.push(0xFD);
+                0x56u32.encode(sink);
+                memarg.encode(sink);
+                assert!(lane < 4);
+                sink.push(lane);
+            }
+            Instruction::V128Load64Lane { memarg, lane } => {
+                sink.push(0xFD);
+                0x57u32.encode(sink);
+                memarg.encode(sink);
+                assert!(lane < 2);
+                sink.push(lane);
+            }
+            Instruction::V128Store8Lane { memarg, lane } => {
+                sink.push(0xFD);
+                0x58u32.encode(sink);
+                memarg.encode(sink);
+                assert!(lane < 16);
+                sink.push(lane);
+            }
+            Instruction::V128Store16Lane { memarg, lane } => {
+                sink.push(0xFD);
+                0x59u32.encode(sink);
+                memarg.encode(sink);
+                assert!(lane < 8);
+                sink.push(lane);
+            }
+            Instruction::V128Store32Lane { memarg, lane } => {
+                sink.push(0xFD);
+                0x5Au32.encode(sink);
+                memarg.encode(sink);
+                assert!(lane < 4);
+                sink.push(lane);
+            }
+            Instruction::V128Store64Lane { memarg, lane } => {
+                sink.push(0xFD);
+                0x5Bu32.encode(sink);
+                memarg.encode(sink);
+                assert!(lane < 2);
+                sink.push(lane);
+            }
+            Instruction::I64x2Eq => {
+                sink.push(0xFD);
+                0xD6u32.encode(sink);
+            }
+            Instruction::I64x2Ne => {
+                sink.push(0xFD);
+                0xD7u32.encode(sink);
+            }
+            Instruction::I64x2LtS => {
+                sink.push(0xFD);
+                0xD8u32.encode(sink);
+            }
+            Instruction::I64x2GtS => {
+                sink.push(0xFD);
+                0xD9u32.encode(sink);
+            }
+            Instruction::I64x2LeS => {
+                sink.push(0xFD);
+                0xDAu32.encode(sink);
+            }
+            Instruction::I64x2GeS => {
+                sink.push(0xFD);
+                0xDBu32.encode(sink);
+            }
+            Instruction::I8x16RelaxedSwizzle => {
+                sink.push(0xFD);
+                0x100u32.encode(sink);
+            }
+            Instruction::I32x4RelaxedTruncF32x4S => {
+                sink.push(0xFD);
+                0x101u32.encode(sink);
+            }
+            Instruction::I32x4RelaxedTruncF32x4U => {
+                sink.push(0xFD);
+                0x102u32.encode(sink);
+            }
+            Instruction::I32x4RelaxedTruncF64x2SZero => {
+                sink.push(0xFD);
+                0x103u32.encode(sink);
+            }
+            Instruction::I32x4RelaxedTruncF64x2UZero => {
+                sink.push(0xFD);
+                0x104u32.encode(sink);
+            }
+            Instruction::F32x4RelaxedMadd => {
+                sink.push(0xFD);
+                0x105u32.encode(sink);
+            }
+            Instruction::F32x4RelaxedNmadd => {
+                sink.push(0xFD);
+                0x106u32.encode(sink);
+            }
+            Instruction::F64x2RelaxedMadd => {
+                sink.push(0xFD);
+                0x107u32.encode(sink);
+            }
+            Instruction::F64x2RelaxedNmadd => {
+                sink.push(0xFD);
+                0x108u32.encode(sink);
+            }
+            Instruction::I8x16RelaxedLaneselect => {
+                sink.push(0xFD);
+                0x109u32.encode(sink);
+            }
+            Instruction::I16x8RelaxedLaneselect => {
+                sink.push(0xFD);
+                0x10Au32.encode(sink);
+            }
+            Instruction::I32x4RelaxedLaneselect => {
+                sink.push(0xFD);
+                0x10Bu32.encode(sink);
+            }
+            Instruction::I64x2RelaxedLaneselect => {
+                sink.push(0xFD);
+                0x10Cu32.encode(sink);
+            }
+            Instruction::F32x4RelaxedMin => {
+                sink.push(0xFD);
+                0x10Du32.encode(sink);
+            }
+            Instruction::F32x4RelaxedMax => {
+                sink.push(0xFD);
+                0x10Eu32.encode(sink);
+            }
+            Instruction::F64x2RelaxedMin => {
+                sink.push(0xFD);
+                0x10Fu32.encode(sink);
+            }
+            Instruction::F64x2RelaxedMax => {
+                sink.push(0xFD);
+                0x110u32.encode(sink);
+            }
+            Instruction::I16x8RelaxedQ15mulrS => {
+                sink.push(0xFD);
+                0x111u32.encode(sink);
+            }
+            Instruction::I16x8RelaxedDotI8x16I7x16S => {
+                sink.push(0xFD);
+                0x112u32.encode(sink);
+            }
+            Instruction::I32x4RelaxedDotI8x16I7x16AddS => {
+                sink.push(0xFD);
+                0x113u32.encode(sink);
+            }
+
+            // Atmoic instructions from the thread proposal
+            Instruction::MemoryAtomicNotify(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x00);
+                memarg.encode(sink);
+            }
+            Instruction::MemoryAtomicWait32(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x01);
+                memarg.encode(sink);
+            }
+            Instruction::MemoryAtomicWait64(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x02);
+                memarg.encode(sink);
+            }
+            Instruction::AtomicFence => {
+                sink.push(0xFE);
+                sink.push(0x03);
+                sink.push(0x00);
+            }
+            Instruction::I32AtomicLoad(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x10);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicLoad(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x11);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicLoad8U(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x12);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicLoad16U(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x13);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicLoad8U(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x14);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicLoad16U(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x15);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicLoad32U(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x16);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicStore(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x17);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicStore(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x18);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicStore8(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x19);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicStore16(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x1A);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicStore8(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x1B);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicStore16(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x1C);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicStore32(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x1D);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmwAdd(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x1E);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmwAdd(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x1F);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw8AddU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x20);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw16AddU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x21);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw8AddU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x22);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw16AddU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x23);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw32AddU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x24);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmwSub(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x25);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmwSub(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x26);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw8SubU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x27);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw16SubU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x28);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw8SubU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x29);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw16SubU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x2A);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw32SubU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x2B);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmwAnd(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x2C);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmwAnd(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x2D);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw8AndU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x2E);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw16AndU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x2F);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw8AndU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x30);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw16AndU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x31);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw32AndU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x32);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmwOr(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x33);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmwOr(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x34);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw8OrU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x35);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw16OrU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x36);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw8OrU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x37);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw16OrU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x38);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw32OrU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x39);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmwXor(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x3A);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmwXor(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x3B);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw8XorU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x3C);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw16XorU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x3D);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw8XorU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x3E);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw16XorU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x3F);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw32XorU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x40);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmwXchg(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x41);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmwXchg(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x42);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw8XchgU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x43);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw16XchgU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x44);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw8XchgU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x45);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw16XchgU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x46);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw32XchgU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x47);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmwCmpxchg(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x48);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmwCmpxchg(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x49);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw8CmpxchgU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x4A);
+                memarg.encode(sink);
+            }
+            Instruction::I32AtomicRmw16CmpxchgU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x4B);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw8CmpxchgU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x4C);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw16CmpxchgU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x4D);
+                memarg.encode(sink);
+            }
+            Instruction::I64AtomicRmw32CmpxchgU(memarg) => {
+                sink.push(0xFE);
+                sink.push(0x4E);
+                memarg.encode(sink);
+            }
+        }
+    }
+}
+
+/// A constant expression.
+///
+/// Usable in contexts such as offsets or initializers.
+#[derive(Debug)]
+pub struct ConstExpr {
+    bytes: Vec<u8>,
+}
+
+impl ConstExpr {
+    /// Create a new empty constant expression builder.
+    pub fn empty() -> Self {
+        Self { bytes: Vec::new() }
+    }
+
+    /// Create a constant expression with the specified raw encoding of instructions.
+    pub fn raw(bytes: impl IntoIterator<Item = u8>) -> Self {
+        Self {
+            bytes: bytes.into_iter().collect(),
+        }
+    }
+
+    fn new_insn(insn: Instruction) -> Self {
+        let mut bytes = vec![];
+        insn.encode(&mut bytes);
+        Self { bytes }
+    }
+
+    /// Create a constant expression containing a single `global.get` instruction.
+    pub fn global_get(index: u32) -> Self {
+        Self::new_insn(Instruction::GlobalGet(index))
+    }
+
+    /// Create a constant expression containing a single `ref.null` instruction.
+    pub fn ref_null(ty: HeapType) -> Self {
+        Self::new_insn(Instruction::RefNull(ty))
+    }
+
+    /// Create a constant expression containing a single `ref.func` instruction.
+    pub fn ref_func(func: u32) -> Self {
+        Self::new_insn(Instruction::RefFunc(func))
+    }
+
+    /// Create a constant expression containing a single `i32.const` instruction.
+    pub fn i32_const(value: i32) -> Self {
+        Self::new_insn(Instruction::I32Const(value))
+    }
+
+    /// Create a constant expression containing a single `i64.const` instruction.
+    pub fn i64_const(value: i64) -> Self {
+        Self::new_insn(Instruction::I64Const(value))
+    }
+
+    /// Create a constant expression containing a single `f32.const` instruction.
+    pub fn f32_const(value: f32) -> Self {
+        Self::new_insn(Instruction::F32Const(value))
+    }
+
+    /// Create a constant expression containing a single `f64.const` instruction.
+    pub fn f64_const(value: f64) -> Self {
+        Self::new_insn(Instruction::F64Const(value))
+    }
+
+    /// Create a constant expression containing a single `v128.const` instruction.
+    pub fn v128_const(value: i128) -> Self {
+        Self::new_insn(Instruction::V128Const(value))
+    }
+}
+
+impl Encode for ConstExpr {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.extend(&self.bytes);
+        Instruction::End.encode(sink);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn function_new_with_locals_test() {
+        use super::*;
+
+        // Test the algorithm for conversion is correct
+        let f1 = Function::new_with_locals_types([
+            ValType::I32,
+            ValType::I32,
+            ValType::I64,
+            ValType::F32,
+            ValType::F32,
+            ValType::F32,
+            ValType::I32,
+            ValType::I64,
+            ValType::I64,
+        ]);
+        let f2 = Function::new([
+            (2, ValType::I32),
+            (1, ValType::I64),
+            (3, ValType::F32),
+            (1, ValType::I32),
+            (2, ValType::I64),
+        ]);
+
+        assert_eq!(f1.bytes, f2.bytes)
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/custom.rs b/third_party/rust/wasm-encoder/src/core/custom.rs
new file mode 100644
index 0000000000..47d78d458c
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/custom.rs
@@ -0,0 +1,53 @@
+use crate::{encoding_size, Encode, Section, SectionId};
+
+/// A custom section holding arbitrary data.
+#[derive(Clone, Debug)]
+pub struct CustomSection<'a> {
+    /// The name of this custom section.
+    pub name: &'a str,
+    /// This custom section's data.
+    pub data: &'a [u8],
+}
+
+impl Encode for CustomSection<'_> {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        let encoded_name_len = encoding_size(u32::try_from(self.name.len()).unwrap());
+        (encoded_name_len + self.name.len() + self.data.len()).encode(sink);
+        self.name.encode(sink);
+        sink.extend(self.data);
+    }
+}
+
+impl Section for CustomSection<'_> {
+    fn id(&self) -> u8 {
+        SectionId::Custom.into()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_custom_section() {
+        let custom = CustomSection {
+            name: "test",
+            data: &[11, 22, 33, 44],
+        };
+
+        let mut encoded = vec![];
+        custom.encode(&mut encoded);
+
+        #[rustfmt::skip]
+        assert_eq!(encoded, vec![
+            // LEB128 length of section.
+            9,
+            // LEB128 length of name.
+            4,
+            // Name.
+            b't', b'e', b's', b't',
+            // Data.
+            11, 22, 33, 44,
+        ]);
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/data.rs b/third_party/rust/wasm-encoder/src/core/data.rs
new file mode 100644
index 0000000000..6439b66e2e
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/data.rs
@@ -0,0 +1,185 @@
+use crate::{encode_section, encoding_size, ConstExpr, Encode, Section, SectionId};
+
+/// An encoder for the data section.
+///
+/// Data sections are only supported for modules.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{
+///     ConstExpr, DataSection, Instruction, MemorySection, MemoryType,
+///     Module,
+/// };
+///
+/// let mut memory = MemorySection::new();
+/// memory.memory(MemoryType {
+///     minimum: 1,
+///     maximum: None,
+///     memory64: false,
+///     shared: false,
+/// });
+///
+/// let mut data = DataSection::new();
+/// let memory_index = 0;
+/// let offset = ConstExpr::i32_const(42);
+/// let segment_data = b"hello";
+/// data.active(memory_index, &offset, segment_data.iter().copied());
+///
+/// let mut module = Module::new();
+/// module
+///     .section(&memory)
+///     .section(&data);
+///
+/// let wasm_bytes = module.finish();
+/// ```
+#[derive(Clone, Default, Debug)]
+pub struct DataSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+/// A segment in the data section.
+#[derive(Clone, Debug)]
+pub struct DataSegment<'a, D> {
+    /// This data segment's mode.
+    pub mode: DataSegmentMode<'a>,
+    /// This data segment's data.
+    pub data: D,
+}
+
+/// A data segment's mode.
+#[derive(Clone, Debug)]
+pub enum DataSegmentMode<'a> {
+    /// An active data segment.
+    Active {
+        /// The memory this segment applies to.
+        memory_index: u32,
+        /// The offset where this segment's data is initialized at.
+        offset: &'a ConstExpr,
+    },
+    /// A passive data segment.
+    ///
+    /// Passive data segments are part of the bulk memory proposal.
+    Passive,
+}
+
+impl DataSection {
+    /// Create a new data section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of data segments in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define a data segment.
+    pub fn segment<D>(&mut self, segment: DataSegment<D>) -> &mut Self
+    where
+        D: IntoIterator<Item = u8>,
+        D::IntoIter: ExactSizeIterator,
+    {
+        match segment.mode {
+            DataSegmentMode::Passive => {
+                self.bytes.push(0x01);
+            }
+            DataSegmentMode::Active {
+                memory_index: 0,
+                offset,
+            } => {
+                self.bytes.push(0x00);
+                offset.encode(&mut self.bytes);
+            }
+            DataSegmentMode::Active {
+                memory_index,
+                offset,
+            } => {
+                self.bytes.push(0x02);
+                memory_index.encode(&mut self.bytes);
+                offset.encode(&mut self.bytes);
+            }
+        }
+
+        let data = segment.data.into_iter();
+        data.len().encode(&mut self.bytes);
+        self.bytes.extend(data);
+
+        self.num_added += 1;
+        self
+    }
+
+    /// Define an active data segment.
+    pub fn active<D>(&mut self, memory_index: u32, offset: &ConstExpr, data: D) -> &mut Self
+    where
+        D: IntoIterator<Item = u8>,
+        D::IntoIter: ExactSizeIterator,
+    {
+        self.segment(DataSegment {
+            mode: DataSegmentMode::Active {
+                memory_index,
+                offset,
+            },
+            data,
+        })
+    }
+
+    /// Define a passive data segment.
+    ///
+    /// Passive data segments are part of the bulk memory proposal.
+    pub fn passive<D>(&mut self, data: D) -> &mut Self
+    where
+        D: IntoIterator<Item = u8>,
+        D::IntoIter: ExactSizeIterator,
+    {
+        self.segment(DataSegment {
+            mode: DataSegmentMode::Passive,
+            data,
+        })
+    }
+
+    /// Copy an already-encoded data segment into this data section.
+    pub fn raw(&mut self, already_encoded_data_segment: &[u8]) -> &mut Self {
+        self.bytes.extend_from_slice(already_encoded_data_segment);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for DataSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl Section for DataSection {
+    fn id(&self) -> u8 {
+        SectionId::Data.into()
+    }
+}
+
+/// An encoder for the data count section.
+#[derive(Clone, Copy, Debug)]
+pub struct DataCountSection {
+    /// The number of segments in the data section.
+    pub count: u32,
+}
+
+impl Encode for DataCountSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encoding_size(self.count).encode(sink);
+        self.count.encode(sink);
+    }
+}
+
+impl Section for DataCountSection {
+    fn id(&self) -> u8 {
+        SectionId::DataCount.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/elements.rs b/third_party/rust/wasm-encoder/src/core/elements.rs
new file mode 100644
index 0000000000..3325c3d429
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/elements.rs
@@ -0,0 +1,227 @@
+use crate::{encode_section, ConstExpr, Encode, RefType, Section, SectionId};
+
+/// An encoder for the element section.
+///
+/// Element sections are only supported for modules.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{
+///     Elements, ElementSection, Module, TableSection, TableType,
+///     RefType, ConstExpr
+/// };
+///
+/// let mut tables = TableSection::new();
+/// tables.table(TableType {
+///     element_type: RefType::FUNCREF,
+///     minimum: 128,
+///     maximum: None,
+/// });
+///
+/// let mut elements = ElementSection::new();
+/// let table_index = 0;
+/// let offset = ConstExpr::i32_const(42);
+/// let element_type = RefType::FUNCREF;
+/// let functions = Elements::Functions(&[
+///     // Function indices...
+/// ]);
+/// elements.active(Some(table_index), &offset, element_type, functions);
+///
+/// let mut module = Module::new();
+/// module
+///     .section(&tables)
+///     .section(&elements);
+///
+/// let wasm_bytes = module.finish();
+/// ```
+#[derive(Clone, Default, Debug)]
+pub struct ElementSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+/// A sequence of elements in a segment in the element section.
+#[derive(Clone, Copy, Debug)]
+pub enum Elements<'a> {
+    /// A sequences of references to functions by their indices.
+    Functions(&'a [u32]),
+    /// A sequence of reference expressions.
+    Expressions(&'a [ConstExpr]),
+}
+
+/// An element segment's mode.
+#[derive(Clone, Debug)]
+pub enum ElementMode<'a> {
+    /// A passive element segment.
+    ///
+    /// Passive segments are part of the bulk memory proposal.
+    Passive,
+    /// A declared element segment.
+    ///
+    /// Declared segments are part of the bulk memory proposal.
+    Declared,
+    /// An active element segment.
+    Active {
+        /// The table index.
+        ///
+        /// `Active` element specifying a `None` table forces the MVP encoding and refers to the
+        /// 0th table holding `funcref`s. Non-`None` tables use the encoding introduced with the
+        /// bulk memory proposal and can refer to tables with any valid reference type.
+        table: Option<u32>,
+        /// The offset within the table to place this segment.
+        offset: &'a ConstExpr,
+    },
+}
+
+/// An element segment in the element section.
+#[derive(Clone, Debug)]
+pub struct ElementSegment<'a> {
+    /// The element segment's mode.
+    pub mode: ElementMode<'a>,
+    /// The element segment's type.
+    pub element_type: RefType,
+    /// This segment's elements.
+    pub elements: Elements<'a>,
+}
+
+impl ElementSection {
+    /// Create a new element section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of element segments in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an element segment.
+    pub fn segment<'a>(&mut self, segment: ElementSegment<'a>) -> &mut Self {
+        let expr_bit = match segment.elements {
+            Elements::Expressions(_) => 0b100u32,
+            Elements::Functions(_) => 0b000u32,
+        };
+        match &segment.mode {
+            ElementMode::Active {
+                table: None,
+                offset,
+            } => {
+                (/* 0x00 | */expr_bit).encode(&mut self.bytes);
+                offset.encode(&mut self.bytes);
+            }
+            ElementMode::Passive => {
+                (0x01 | expr_bit).encode(&mut self.bytes);
+                if expr_bit == 0 {
+                    self.bytes.push(0x00); // elemkind == funcref
+                } else {
+                    segment.element_type.encode(&mut self.bytes);
+                }
+            }
+            ElementMode::Active {
+                table: Some(i),
+                offset,
+            } => {
+                (0x02 | expr_bit).encode(&mut self.bytes);
+                i.encode(&mut self.bytes);
+                offset.encode(&mut self.bytes);
+                if expr_bit == 0 {
+                    self.bytes.push(0x00); // elemkind == funcref
+                } else {
+                    segment.element_type.encode(&mut self.bytes);
+                }
+            }
+            ElementMode::Declared => {
+                (0x03 | expr_bit).encode(&mut self.bytes);
+                if expr_bit == 0 {
+                    self.bytes.push(0x00); // elemkind == funcref
+                } else {
+                    segment.element_type.encode(&mut self.bytes);
+                }
+            }
+        }
+
+        match segment.elements {
+            Elements::Functions(fs) => {
+                fs.encode(&mut self.bytes);
+            }
+            Elements::Expressions(e) => {
+                e.len().encode(&mut self.bytes);
+                for expr in e {
+                    expr.encode(&mut self.bytes);
+                }
+            }
+        }
+
+        self.num_added += 1;
+        self
+    }
+
+    /// Define an active element segment.
+    ///
+    /// `Active` element specifying a `None` table forces the MVP encoding and refers to the 0th
+    /// table holding `funcref`s. Non-`None` tables use the encoding introduced with the bulk
+    /// memory proposal and can refer to tables with any valid reference type.
+    pub fn active(
+        &mut self,
+        table_index: Option<u32>,
+        offset: &ConstExpr,
+        element_type: RefType,
+        elements: Elements<'_>,
+    ) -> &mut Self {
+        self.segment(ElementSegment {
+            mode: ElementMode::Active {
+                table: table_index,
+                offset,
+            },
+            element_type,
+            elements,
+        })
+    }
+
+    /// Encode a passive element segment.
+    ///
+    /// Passive segments are part of the bulk memory proposal.
+    pub fn passive<'a>(&mut self, element_type: RefType, elements: Elements<'a>) -> &mut Self {
+        self.segment(ElementSegment {
+            mode: ElementMode::Passive,
+            element_type,
+            elements,
+        })
+    }
+
+    /// Encode a declared element segment.
+    ///
+    /// Declared segments are part of the bulk memory proposal.
+    pub fn declared<'a>(&mut self, element_type: RefType, elements: Elements<'a>) -> &mut Self {
+        self.segment(ElementSegment {
+            mode: ElementMode::Declared,
+            element_type,
+            elements,
+        })
+    }
+
+    /// Copy a raw, already-encoded element segment into this elements section.
+    pub fn raw(&mut self, raw_bytes: &[u8]) -> &mut Self {
+        self.bytes.extend_from_slice(raw_bytes);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for ElementSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl Section for ElementSection {
+    fn id(&self) -> u8 {
+        SectionId::Element.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/exports.rs b/third_party/rust/wasm-encoder/src/core/exports.rs
new file mode 100644
index 0000000000..36c7896362
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/exports.rs
@@ -0,0 +1,85 @@
+use super::{
+    CORE_FUNCTION_SORT, CORE_GLOBAL_SORT, CORE_MEMORY_SORT, CORE_TABLE_SORT, CORE_TAG_SORT,
+};
+use crate::{encode_section, Encode, Section, SectionId};
+
+/// Represents the kind of an export from a WebAssembly module.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[repr(u8)]
+pub enum ExportKind {
+    /// The export is a function.
+    Func = CORE_FUNCTION_SORT,
+    /// The export is a table.
+    Table = CORE_TABLE_SORT,
+    /// The export is a memory.
+    Memory = CORE_MEMORY_SORT,
+    /// The export is a global.
+    Global = CORE_GLOBAL_SORT,
+    /// The export is a tag.
+    Tag = CORE_TAG_SORT,
+}
+
+impl Encode for ExportKind {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(*self as u8);
+    }
+}
+
+/// An encoder for the export section of WebAssembly module.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Module, ExportSection, ExportKind};
+///
+/// let mut exports = ExportSection::new();
+/// exports.export("foo", ExportKind::Func, 0);
+///
+/// let mut module = Module::new();
+/// module.section(&exports);
+///
+/// let bytes = module.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct ExportSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl ExportSection {
+    /// Create a new export section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of exports in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an export in the export section.
+    pub fn export(&mut self, name: &str, kind: ExportKind, index: u32) -> &mut Self {
+        name.encode(&mut self.bytes);
+        kind.encode(&mut self.bytes);
+        index.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for ExportSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl Section for ExportSection {
+    fn id(&self) -> u8 {
+        SectionId::Export.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/functions.rs b/third_party/rust/wasm-encoder/src/core/functions.rs
new file mode 100644
index 0000000000..e21d8c10a7
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/functions.rs
@@ -0,0 +1,63 @@
+use crate::{encode_section, Encode, Section, SectionId};
+
+/// An encoder for the function section of WebAssembly modules.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{Module, FunctionSection, ValType};
+///
+/// let mut functions = FunctionSection::new();
+/// let type_index = 0;
+/// functions.function(type_index);
+///
+/// let mut module = Module::new();
+/// module.section(&functions);
+///
+/// // Note: this will generate an invalid module because we didn't generate a
+/// // code section containing the function body. See the documentation for
+/// // `CodeSection` for details.
+///
+/// let bytes = module.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct FunctionSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl FunctionSection {
+    /// Construct a new module function section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of functions in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define a function in a module's function section.
+    pub fn function(&mut self, type_index: u32) -> &mut Self {
+        type_index.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for FunctionSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl Section for FunctionSection {
+    fn id(&self) -> u8 {
+        SectionId::Function.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/globals.rs b/third_party/rust/wasm-encoder/src/core/globals.rs
new file mode 100644
index 0000000000..16f23c2891
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/globals.rs
@@ -0,0 +1,90 @@
+use crate::{encode_section, ConstExpr, Encode, Section, SectionId, ValType};
+
+/// An encoder for the global section.
+///
+/// Global sections are only supported for modules.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{ConstExpr, Module, GlobalSection, GlobalType, Instruction, ValType};
+///
+/// let mut globals = GlobalSection::new();
+/// globals.global(
+///     GlobalType {
+///         val_type: ValType::I32,
+///         mutable: false,
+///     },
+///     &ConstExpr::i32_const(42),
+/// );
+///
+/// let mut module = Module::new();
+/// module.section(&globals);
+///
+/// let wasm_bytes = module.finish();
+/// ```
+#[derive(Clone, Default, Debug)]
+pub struct GlobalSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl GlobalSection {
+    /// Create a new global section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of globals in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define a global.
+    pub fn global(&mut self, global_type: GlobalType, init_expr: &ConstExpr) -> &mut Self {
+        global_type.encode(&mut self.bytes);
+        init_expr.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+
+    /// Add a raw byte slice into this code section as a global.
+    pub fn raw(&mut self, data: &[u8]) -> &mut Self {
+        self.bytes.extend(data);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for GlobalSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl Section for GlobalSection {
+    fn id(&self) -> u8 {
+        SectionId::Global.into()
+    }
+}
+
+/// A global's type.
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+pub struct GlobalType {
+    /// This global's value type.
+    pub val_type: ValType,
+    /// Whether this global is mutable or not.
+    pub mutable: bool,
+}
+
+impl Encode for GlobalType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.val_type.encode(sink);
+        sink.push(self.mutable as u8);
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/imports.rs b/third_party/rust/wasm-encoder/src/core/imports.rs
new file mode 100644
index 0000000000..455170f227
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/imports.rs
@@ -0,0 +1,142 @@
+use crate::{
+    encode_section, Encode, GlobalType, MemoryType, Section, SectionId, TableType, TagType,
+    CORE_FUNCTION_SORT, CORE_GLOBAL_SORT, CORE_MEMORY_SORT, CORE_TABLE_SORT, CORE_TAG_SORT,
+};
+
+/// The type of an entity.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum EntityType {
+    /// A function type.
+    ///
+    /// The value is an index into the types section.
+    Function(u32),
+    /// A table type.
+    Table(TableType),
+    /// A memory type.
+    Memory(MemoryType),
+    /// A global type.
+    Global(GlobalType),
+    /// A tag type.
+    ///
+    /// This variant is used with the exception handling proposal.
+    Tag(TagType),
+}
+
+impl Encode for EntityType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Self::Function(i) => {
+                sink.push(CORE_FUNCTION_SORT);
+                i.encode(sink);
+            }
+            Self::Table(t) => {
+                sink.push(CORE_TABLE_SORT);
+                t.encode(sink);
+            }
+            Self::Memory(t) => {
+                sink.push(CORE_MEMORY_SORT);
+                t.encode(sink);
+            }
+            Self::Global(t) => {
+                sink.push(CORE_GLOBAL_SORT);
+                t.encode(sink);
+            }
+            Self::Tag(t) => {
+                sink.push(CORE_TAG_SORT);
+                t.encode(sink);
+            }
+        }
+    }
+}
+
+impl From<TableType> for EntityType {
+    fn from(t: TableType) -> Self {
+        Self::Table(t)
+    }
+}
+
+impl From<MemoryType> for EntityType {
+    fn from(t: MemoryType) -> Self {
+        Self::Memory(t)
+    }
+}
+
+impl From<GlobalType> for EntityType {
+    fn from(t: GlobalType) -> Self {
+        Self::Global(t)
+    }
+}
+
+impl From<TagType> for EntityType {
+    fn from(t: TagType) -> Self {
+        Self::Tag(t)
+    }
+}
+
+/// An encoder for the import section of WebAssembly modules.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{MemoryType, Module, ImportSection};
+///
+/// let mut imports = ImportSection::new();
+/// imports.import(
+///     "env",
+///     "memory",
+///     MemoryType {
+///         minimum: 1,
+///         maximum: None,
+///         memory64: false,
+///         shared: false,
+///     }
+/// );
+///
+/// let mut module = Module::new();
+/// module.section(&imports);
+///
+/// let bytes = module.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct ImportSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl ImportSection {
+    /// Create a new import section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of imports in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define an import in the import section.
+    pub fn import(&mut self, module: &str, field: &str, ty: impl Into<EntityType>) -> &mut Self {
+        module.encode(&mut self.bytes);
+        field.encode(&mut self.bytes);
+        ty.into().encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for ImportSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl Section for ImportSection {
+    fn id(&self) -> u8 {
+        SectionId::Import.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/linking.rs b/third_party/rust/wasm-encoder/src/core/linking.rs
new file mode 100644
index 0000000000..3309277be3
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/linking.rs
@@ -0,0 +1,261 @@
+use crate::{encode_section, CustomSection, Encode, Section, SectionId};
+
+const VERSION: u32 = 2;
+
+/// An encoder for the [linking custom
+/// section](https://github.com/WebAssembly/tool-conventions/blob/master/Linking.md#linking-metadata-section).
+///
+/// This section is a non-standard convention that is supported by the LLVM
+/// toolchain. It, along with associated "reloc.*" custom sections, allows you
+/// to treat a Wasm module as a low-level object file that can be linked with
+/// other Wasm object files to produce a final, complete Wasm module.
+///
+/// The linking section must come before the reloc sections.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{LinkingSection, Module, SymbolTable};
+///
+/// // Create a new linking section.
+/// let mut linking = LinkingSection::new();
+///
+/// // Define a symbol table.
+/// let mut sym_tab = SymbolTable::new();
+///
+/// // Define a function symbol in the symbol table.
+/// let flags = SymbolTable::WASM_SYM_BINDING_LOCAL | SymbolTable::WASM_SYM_EXPORTED;
+/// let func_index = 42;
+/// let sym_name = "my_exported_func";
+/// sym_tab.function(flags, func_index, Some(sym_name));
+///
+/// // Add the symbol table to our linking section.
+/// linking.symbol_table(&sym_tab);
+///
+/// // Add the linking section to a new Wasm module and get the encoded bytes.
+/// let mut module = Module::new();
+/// module.section(&linking);
+/// let wasm_bytes = module.finish();
+/// ```
+#[derive(Clone, Debug)]
+pub struct LinkingSection {
+    bytes: Vec<u8>,
+}
+
+impl LinkingSection {
+    /// Construct a new encoder for the linking custom section.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    // TODO: `fn segment_info` for the `WASM_SEGMENT_INFO` linking subsection.
+
+    // TODO: `fn init_funcs` for the `WASM_INIT_FUNCS` linking subsection.
+
+    // TODO: `fn comdat_info` for the `WASM_COMDAT_INFO` linking subsection.
+
+    /// Add a symbol table subsection.
+    pub fn symbol_table(&mut self, symbol_table: &SymbolTable) -> &mut Self {
+        symbol_table.encode(&mut self.bytes);
+        self
+    }
+}
+
+impl Default for LinkingSection {
+    fn default() -> Self {
+        let mut bytes = Vec::new();
+        VERSION.encode(&mut bytes);
+        Self { bytes }
+    }
+}
+
+impl Encode for LinkingSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        CustomSection {
+            name: "linking",
+            data: &self.bytes,
+        }
+        .encode(sink);
+    }
+}
+
+impl Section for LinkingSection {
+    fn id(&self) -> u8 {
+        SectionId::Custom.into()
+    }
+}
+
+#[allow(unused)]
+const WASM_SEGMENT_INFO: u8 = 5;
+#[allow(unused)]
+const WASM_INIT_FUNCS: u8 = 6;
+#[allow(unused)]
+const WASM_COMDAT_INFO: u8 = 7;
+const WASM_SYMBOL_TABLE: u8 = 8;
+
+/// A subsection of the [linking custom section][crate::LinkingSection] that
+/// provides extra information about the symbols present in this Wasm object
+/// file.
+#[derive(Clone, Debug, Default)]
+pub struct SymbolTable {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+const SYMTAB_FUNCTION: u32 = 0;
+const SYMTAB_DATA: u32 = 1;
+const SYMTAB_GLOBAL: u32 = 2;
+#[allow(unused)]
+const SYMTAB_SECTION: u32 = 3;
+#[allow(unused)]
+const SYMTAB_TAG: u32 = 4;
+const SYMTAB_TABLE: u32 = 5;
+
+impl SymbolTable {
+    /// Construct a new symbol table subsection encoder.
+    pub fn new() -> Self {
+        SymbolTable {
+            bytes: vec![],
+            num_added: 0,
+        }
+    }
+
+    /// Define a function symbol in this symbol table.
+    ///
+    /// The `name` must be omitted if `index` references an imported table and
+    /// the `WASM_SYM_EXPLICIT_NAME` flag is not set.
+    pub fn function(&mut self, flags: u32, index: u32, name: Option<&str>) -> &mut Self {
+        SYMTAB_FUNCTION.encode(&mut self.bytes);
+        flags.encode(&mut self.bytes);
+        index.encode(&mut self.bytes);
+        if let Some(name) = name {
+            name.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+
+    /// Define a global symbol in this symbol table.
+    ///
+    /// The `name` must be omitted if `index` references an imported table and
+    /// the `WASM_SYM_EXPLICIT_NAME` flag is not set.
+    pub fn global(&mut self, flags: u32, index: u32, name: Option<&str>) -> &mut Self {
+        SYMTAB_GLOBAL.encode(&mut self.bytes);
+        flags.encode(&mut self.bytes);
+        index.encode(&mut self.bytes);
+        if let Some(name) = name {
+            name.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+
+    // TODO: tags
+
+    /// Define a table symbol in this symbol table.
+    ///
+    /// The `name` must be omitted if `index` references an imported table and
+    /// the `WASM_SYM_EXPLICIT_NAME` flag is not set.
+    pub fn table(&mut self, flags: u32, index: u32, name: Option<&str>) -> &mut Self {
+        SYMTAB_TABLE.encode(&mut self.bytes);
+        flags.encode(&mut self.bytes);
+        index.encode(&mut self.bytes);
+        if let Some(name) = name {
+            name.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+
+    /// Add a data symbol to this symbol table.
+    pub fn data(
+        &mut self,
+        flags: u32,
+        name: &str,
+        definition: Option<DataSymbolDefinition>,
+    ) -> &mut Self {
+        SYMTAB_DATA.encode(&mut self.bytes);
+        flags.encode(&mut self.bytes);
+        name.encode(&mut self.bytes);
+        if let Some(def) = definition {
+            def.index.encode(&mut self.bytes);
+            def.offset.encode(&mut self.bytes);
+            def.size.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+
+    // TODO: sections
+
+    /// This is a weak symbol.
+    ///
+    /// This flag is mutually exclusive with `WASM_SYM_BINDING_LOCAL`.
+    ///
+    /// When linking multiple modules defining the same symbol, all weak
+    /// definitions are discarded if any strong definitions exist; then if
+    /// multiple weak definitions exist all but one (unspecified) are discarded;
+    /// and finally it is an error if more than one definition remains.
+    pub const WASM_SYM_BINDING_WEAK: u32 = 0x1;
+
+    /// This is a local symbol.
+    ///
+    /// This flag is mutually exclusive with `WASM_SYM_BINDING_WEAK`.
+    ///
+    /// Local symbols are not to be exported, or linked to other
+    /// modules/sections. The names of all non-local symbols must be unique, but
+    /// the names of local symbols are not considered for uniqueness. A local
+    /// function or global symbol cannot reference an import.
+    pub const WASM_SYM_BINDING_LOCAL: u32 = 0x02;
+
+    /// This is a hidden symbol.
+    ///
+    /// Hidden symbols are not to be exported when performing the final link,
+    /// but may be linked to other modules.
+    pub const WASM_SYM_VISIBILITY_HIDDEN: u32 = 0x04;
+
+    /// This symbol is not defined.
+    ///
+    /// For non-data symbols, this must match whether the symbol is an import or
+    /// is defined; for data symbols, determines whether a segment is specified.
+    pub const WASM_SYM_UNDEFINED: u32 = 0x10;
+
+    /// This symbol is intended to be exported from the wasm module to the host
+    /// environment.
+    ///
+    /// This differs from the visibility flags in that it effects the static
+    /// linker.
+    pub const WASM_SYM_EXPORTED: u32 = 0x20;
+
+    /// This symbol uses an explicit symbol name, rather than reusing the name
+    /// from a wasm import.
+    ///
+    /// This allows it to remap imports from foreign WebAssembly modules into
+    /// local symbols with different names.
+    pub const WASM_SYM_EXPLICIT_NAME: u32 = 0x40;
+
+    /// This symbol is intended to be included in the linker output, regardless
+    /// of whether it is used by the program.
+    pub const WASM_SYM_NO_STRIP: u32 = 0x80;
+}
+
+impl Encode for SymbolTable {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(WASM_SYMBOL_TABLE);
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+/// The definition of a data symbol within a symbol table.
+#[derive(Clone, Debug)]
+pub struct DataSymbolDefinition {
+    /// The index of the data segment that this symbol is in.
+    pub index: u32,
+    /// The offset of this symbol within its segment.
+    pub offset: u32,
+    /// The byte size (which can be zero) of this data symbol.
+    ///
+    /// Note that `offset + size` must be less than or equal to the segment's
+    /// size.
+    pub size: u32,
+}
diff --git a/third_party/rust/wasm-encoder/src/core/memories.rs b/third_party/rust/wasm-encoder/src/core/memories.rs
new file mode 100644
index 0000000000..c651768bdc
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/memories.rs
@@ -0,0 +1,99 @@
+use crate::{encode_section, Encode, Section, SectionId};
+
+/// An encoder for the memory section.
+///
+/// Memory sections are only supported for modules.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{Module, MemorySection, MemoryType};
+///
+/// let mut memories = MemorySection::new();
+/// memories.memory(MemoryType {
+///     minimum: 1,
+///     maximum: None,
+///     memory64: false,
+///     shared: false,
+/// });
+///
+/// let mut module = Module::new();
+/// module.section(&memories);
+///
+/// let wasm_bytes = module.finish();
+/// ```
+#[derive(Clone, Default, Debug)]
+pub struct MemorySection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl MemorySection {
+    /// Create a new memory section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of memories in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define a memory.
+    pub fn memory(&mut self, memory_type: MemoryType) -> &mut Self {
+        memory_type.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for MemorySection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl Section for MemorySection {
+    fn id(&self) -> u8 {
+        SectionId::Memory.into()
+    }
+}
+
+/// A memory's type.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub struct MemoryType {
+    /// Minimum size, in pages, of this memory
+    pub minimum: u64,
+    /// Maximum size, in pages, of this memory
+    pub maximum: Option<u64>,
+    /// Whether or not this is a 64-bit memory.
+    pub memory64: bool,
+    /// Whether or not this memory is shared.
+    pub shared: bool,
+}
+
+impl Encode for MemoryType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        let mut flags = 0;
+        if self.maximum.is_some() {
+            flags |= 0b001;
+        }
+        if self.shared {
+            flags |= 0b010;
+        }
+        if self.memory64 {
+            flags |= 0b100;
+        }
+
+        sink.push(flags);
+        self.minimum.encode(sink);
+        if let Some(max) = self.maximum {
+            max.encode(sink);
+        }
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/names.rs b/third_party/rust/wasm-encoder/src/core/names.rs
new file mode 100644
index 0000000000..a1c31506fd
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/names.rs
@@ -0,0 +1,263 @@
+use crate::{encoding_size, CustomSection, Encode, Section, SectionId};
+
+/// An encoder for the custom `name` section.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{Module, NameSection, NameMap};
+///
+/// let mut names = NameSection::new();
+/// names.module("the module name");
+///
+/// let mut function_names = NameMap::new();
+/// function_names.append(0, "name of function 0");
+/// function_names.append(1, "a better function");
+/// function_names.append(3, "the best function");
+/// names.functions(&function_names);
+///
+/// let mut module = Module::new();
+/// module.section(&names);
+///
+/// let wasm_bytes = module.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct NameSection {
+    bytes: Vec<u8>,
+}
+
+enum Subsection {
+    // Currently specified in the wasm spec's appendix
+    Module = 0,
+    Function = 1,
+    Local = 2,
+
+    // specified as part of the extended name section proposal
+    //
+    // https://github.com/WebAssembly/extended-name-section/blob/main/proposals/extended-name-section/Overview.md
+    Label = 3,
+    Type = 4,
+    Table = 5,
+    Memory = 6,
+    Global = 7,
+    Element = 8,
+    Data = 9,
+}
+
+impl NameSection {
+    /// Creates a new blank `name` custom section.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Appends a module name subsection to this section.
+    ///
+    /// This will indicate that the name of the entire module should be the
+    /// `name` specified. Note that this should be encoded first before other
+    /// subsections.
+    pub fn module(&mut self, name: &str) {
+        let len = encoding_size(u32::try_from(name.len()).unwrap());
+        self.subsection_header(Subsection::Module, len + name.len());
+        name.encode(&mut self.bytes);
+    }
+
+    /// Appends a subsection for the names of all functions in this wasm module.
+    ///
+    /// Function names are declared in the `names` map provided where the index
+    /// in the map corresponds to the wasm index of the function. This section
+    /// should come after the module name subsection (if present) and before the
+    /// locals subsection (if present).
+    pub fn functions(&mut self, names: &NameMap) {
+        self.subsection_header(Subsection::Function, names.size());
+        names.encode(&mut self.bytes);
+    }
+
+    /// Appends a subsection for the names of locals within functions in the
+    /// wasm module.
+    ///
+    /// This section should come after the function name subsection (if present)
+    /// and before the labels subsection (if present).
+    pub fn locals(&mut self, names: &IndirectNameMap) {
+        self.subsection_header(Subsection::Local, names.size());
+        names.encode(&mut self.bytes);
+    }
+
+    /// Appends a subsection for the names of labels within functions in the
+    /// wasm module.
+    ///
+    /// This section should come after the local name subsection (if present)
+    /// and before the type subsection (if present).
+    pub fn labels(&mut self, names: &IndirectNameMap) {
+        self.subsection_header(Subsection::Label, names.size());
+        names.encode(&mut self.bytes);
+    }
+
+    /// Appends a subsection for the names of all types in this wasm module.
+    ///
+    /// This section should come after the label name subsection (if present)
+    /// and before the table subsection (if present).
+    pub fn types(&mut self, names: &NameMap) {
+        self.subsection_header(Subsection::Type, names.size());
+        names.encode(&mut self.bytes);
+    }
+
+    /// Appends a subsection for the names of all tables in this wasm module.
+    ///
+    /// This section should come after the type name subsection (if present)
+    /// and before the memory subsection (if present).
+    pub fn tables(&mut self, names: &NameMap) {
+        self.subsection_header(Subsection::Table, names.size());
+        names.encode(&mut self.bytes);
+    }
+
+    /// Appends a subsection for the names of all memories in this wasm module.
+    ///
+    /// This section should come after the table name subsection (if present)
+    /// and before the global subsection (if present).
+    pub fn memories(&mut self, names: &NameMap) {
+        self.subsection_header(Subsection::Memory, names.size());
+        names.encode(&mut self.bytes);
+    }
+
+    /// Appends a subsection for the names of all globals in this wasm module.
+    ///
+    /// This section should come after the memory name subsection (if present)
+    /// and before the element subsection (if present).
+    pub fn globals(&mut self, names: &NameMap) {
+        self.subsection_header(Subsection::Global, names.size());
+        names.encode(&mut self.bytes);
+    }
+
+    /// Appends a subsection for the names of all elements in this wasm module.
+    ///
+    /// This section should come after the global name subsection (if present)
+    /// and before the data subsection (if present).
+    pub fn elements(&mut self, names: &NameMap) {
+        self.subsection_header(Subsection::Element, names.size());
+        names.encode(&mut self.bytes);
+    }
+
+    /// Appends a subsection for the names of all data in this wasm module.
+    ///
+    /// This section should come after the element name subsection (if present).
+    pub fn data(&mut self, names: &NameMap) {
+        self.subsection_header(Subsection::Data, names.size());
+        names.encode(&mut self.bytes);
+    }
+
+    fn subsection_header(&mut self, id: Subsection, len: usize) {
+        self.bytes.push(id as u8);
+        len.encode(&mut self.bytes);
+    }
+
+    /// View the encoded section as a CustomSection.
+    pub fn as_custom<'a>(&'a self) -> CustomSection<'a> {
+        CustomSection {
+            name: "name",
+            data: &self.bytes,
+        }
+    }
+}
+
+impl Encode for NameSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.as_custom().encode(sink);
+    }
+}
+
+impl Section for NameSection {
+    fn id(&self) -> u8 {
+        SectionId::Custom.into()
+    }
+}
+
+/// A map used to name items in a wasm module, organized by naming each
+/// individual index.
+///
+/// This is used in conjunction with [`NameSection::functions`] and simlar
+/// methods.
+#[derive(Clone, Debug, Default)]
+pub struct NameMap {
+    bytes: Vec<u8>,
+    count: u32,
+}
+
+impl NameMap {
+    /// Creates a new empty `NameMap`.
+    pub fn new() -> NameMap {
+        NameMap {
+            bytes: vec![],
+            count: 0,
+        }
+    }
+
+    /// Adds a an entry where the item at `idx` has the `name` specified.
+    ///
+    /// Note that indices should be appended in ascending order of the index
+    /// value. Each index may only be named once, but not all indices must be
+    /// named (e.g. `0 foo; 1 bar; 7 qux` is valid but `0 foo; 0 bar` is not).
+    /// Names do not have to be unique (e.g. `0 foo; 1 foo; 2 foo` is valid).
+    pub fn append(&mut self, idx: u32, name: &str) {
+        idx.encode(&mut self.bytes);
+        name.encode(&mut self.bytes);
+        self.count += 1;
+    }
+
+    pub(crate) fn size(&self) -> usize {
+        encoding_size(self.count) + self.bytes.len()
+    }
+
+    /// Returns whether no names have been added to this map.
+    pub fn is_empty(&self) -> bool {
+        self.count == 0
+    }
+}
+
+impl Encode for NameMap {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.count.encode(sink);
+        sink.extend(&self.bytes);
+    }
+}
+
+/// A map used to describe names with two levels of indirection, as opposed to a
+/// [`NameMap`] which has one level of indirection.
+///
+/// This naming map is used with [`NameSection::locals`], for example.
+#[derive(Clone, Debug, Default)]
+pub struct IndirectNameMap {
+    bytes: Vec<u8>,
+    count: u32,
+}
+
+impl IndirectNameMap {
+    /// Creates a new empty name map.
+    pub fn new() -> IndirectNameMap {
+        IndirectNameMap {
+            bytes: vec![],
+            count: 0,
+        }
+    }
+
+    /// Adds a new entry where the item at `idx` has sub-items named within
+    /// `names` as specified.
+    ///
+    /// For example if this is describing local names then `idx` is a function
+    /// index where the indexes within `names` are local indices.
+    pub fn append(&mut self, idx: u32, names: &NameMap) {
+        idx.encode(&mut self.bytes);
+        names.encode(&mut self.bytes);
+        self.count += 1;
+    }
+
+    fn size(&self) -> usize {
+        encoding_size(self.count) + self.bytes.len()
+    }
+}
+
+impl Encode for IndirectNameMap {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.count.encode(sink);
+        sink.extend(&self.bytes);
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/producers.rs b/third_party/rust/wasm-encoder/src/core/producers.rs
new file mode 100644
index 0000000000..ace908a7bd
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/producers.rs
@@ -0,0 +1,178 @@
+use crate::{CustomSection, Encode, Section, SectionId};
+
+/// An encoder for the [producers custom
+/// section](https://github.com/WebAssembly/tool-conventions/blob/main/ProducersSection.md).
+///
+/// This section is a non-standard convention that is supported by many toolchains.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{ProducersSection, ProducersField, Module};
+///
+/// // Create a new producers section.
+/// let mut field = ProducersField::new();
+/// field.value("clang", "14.0.4");
+/// field.value("rustc", "1.66.1 (90743e729 2023-01-10)");
+/// let mut producers = ProducersSection::new();
+/// producers.field("processed-by", &field);
+///
+/// // Add the producers section to a new Wasm module and get the encoded bytes.
+/// let mut module = Module::new();
+/// module.section(&producers);
+/// let wasm_bytes = module.finish();
+/// ```
+#[derive(Clone, Debug)]
+pub struct ProducersSection {
+    bytes: Vec<u8>,
+    num_fields: u32,
+}
+
+impl ProducersSection {
+    /// Construct an empty encoder for the producers custom section.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Add a field to the section. The spec recommends names for this section
+    /// are "language", "processed-by", and "sdk".  Each field in section must
+    /// have a unique name.
+    pub fn field(&mut self, name: &str, values: &ProducersField) -> &mut Self {
+        name.encode(&mut self.bytes);
+        values.encode(&mut self.bytes);
+        self.num_fields += 1;
+        self
+    }
+}
+
+impl Default for ProducersSection {
+    fn default() -> Self {
+        Self {
+            bytes: Vec::new(),
+            num_fields: 0,
+        }
+    }
+}
+
+impl Encode for ProducersSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        let mut data = Vec::new();
+        self.num_fields.encode(&mut data);
+        data.extend(&self.bytes);
+
+        CustomSection {
+            name: "producers",
+            data: &data,
+        }
+        .encode(sink);
+    }
+}
+
+impl Section for ProducersSection {
+    fn id(&self) -> u8 {
+        SectionId::Custom.into()
+    }
+}
+
+/// The value of a field in the producers custom section
+#[derive(Clone, Debug)]
+pub struct ProducersField {
+    bytes: Vec<u8>,
+    num_values: u32,
+}
+
+impl ProducersField {
+    /// Construct an empty encoder for a producers field value
+    pub fn new() -> Self {
+        ProducersField::default()
+    }
+
+    /// Add a value to the field encoder. Each value in a field must have a
+    /// unique name. If there is no sensible value for `version`, use the
+    /// empty string.
+    pub fn value(&mut self, name: &str, version: &str) -> &mut Self {
+        name.encode(&mut self.bytes);
+        version.encode(&mut self.bytes);
+        self.num_values += 1;
+        self
+    }
+}
+
+impl Default for ProducersField {
+    fn default() -> Self {
+        Self {
+            bytes: Vec::new(),
+            num_values: 0,
+        }
+    }
+}
+
+impl Encode for ProducersField {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.num_values.encode(sink);
+        sink.extend(&self.bytes);
+    }
+}
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn roundtrip_example() {
+        use crate::{Module, ProducersField, ProducersSection};
+        use wasmparser::{Parser, Payload, ProducersSectionReader};
+
+        // Create a new producers section.
+        let mut field = ProducersField::new();
+        field.value("clang", "14.0.4");
+        field.value("rustc", "1.66.1");
+        let mut producers = ProducersSection::new();
+        producers.field("processed-by", &field);
+
+        // Add the producers section to a new Wasm module and get the encoded bytes.
+        let mut module = Module::new();
+        module.section(&producers);
+        let wasm_bytes = module.finish();
+
+        let mut parser = Parser::new(0).parse_all(&wasm_bytes);
+        let payload = parser
+            .next()
+            .expect("parser is not empty")
+            .expect("element is a payload");
+        match payload {
+            Payload::Version { .. } => {}
+            _ => panic!(""),
+        }
+        let payload = parser
+            .next()
+            .expect("parser is not empty")
+            .expect("element is a payload");
+        match payload {
+            Payload::CustomSection(c) => {
+                assert_eq!(c.name(), "producers");
+                let mut section = ProducersSectionReader::new(c.data(), c.data_offset())
+                    .expect("readable as a producers section")
+                    .into_iter();
+                let field = section
+                    .next()
+                    .expect("section has an element")
+                    .expect("element is a producers field");
+                assert_eq!(field.name, "processed-by");
+                let mut values = field.values.into_iter();
+                let value = values
+                    .next()
+                    .expect("values has an element")
+                    .expect("element is a producers field value");
+                assert_eq!(value.name, "clang");
+                assert_eq!(value.version, "14.0.4");
+
+                let value = values
+                    .next()
+                    .expect("values has another element")
+                    .expect("element is a producers field value");
+                assert_eq!(value.name, "rustc");
+                assert_eq!(value.version, "1.66.1");
+            }
+            _ => panic!("unexpected payload"),
+        }
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/start.rs b/third_party/rust/wasm-encoder/src/core/start.rs
new file mode 100644
index 0000000000..8f12c0d0ef
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/start.rs
@@ -0,0 +1,39 @@
+use crate::{encoding_size, Encode, Section, SectionId};
+
+/// An encoder for the start section of WebAssembly modules.
+///
+/// # Example
+///
+/// Note: this doesn't actually define the function at index 0, its type, or its
+/// code body, so the resulting Wasm module will be invalid. See `TypeSection`,
+/// `FunctionSection`, and `CodeSection` for details on how to generate those
+/// things.
+///
+/// ```
+/// use wasm_encoder::{Module, StartSection};
+///
+/// let start = StartSection { function_index: 0 };
+///
+/// let mut module = Module::new();
+/// module.section(&start);
+///
+/// let wasm_bytes = module.finish();
+/// ```
+#[derive(Clone, Copy, Debug)]
+pub struct StartSection {
+    /// The index of the start function.
+    pub function_index: u32,
+}
+
+impl Encode for StartSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encoding_size(self.function_index).encode(sink);
+        self.function_index.encode(sink);
+    }
+}
+
+impl Section for StartSection {
+    fn id(&self) -> u8 {
+        SectionId::Start.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/tables.rs b/third_party/rust/wasm-encoder/src/core/tables.rs
new file mode 100644
index 0000000000..cbb2048a64
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/tables.rs
@@ -0,0 +1,104 @@
+use crate::{encode_section, ConstExpr, Encode, RefType, Section, SectionId};
+
+/// An encoder for the table section.
+///
+/// Table sections are only supported for modules.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{Module, TableSection, TableType, RefType};
+///
+/// let mut tables = TableSection::new();
+/// tables.table(TableType {
+///     element_type: RefType::FUNCREF,
+///     minimum: 128,
+///     maximum: None,
+/// });
+///
+/// let mut module = Module::new();
+/// module.section(&tables);
+///
+/// let wasm_bytes = module.finish();
+/// ```
+#[derive(Clone, Default, Debug)]
+pub struct TableSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl TableSection {
+    /// Construct a new table section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of tables in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define a table.
+    pub fn table(&mut self, table_type: TableType) -> &mut Self {
+        table_type.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+
+    /// Define a table with an explicit initialization expression.
+    ///
+    /// Note that this is part of the function-references proposal.
+    pub fn table_with_init(&mut self, table_type: TableType, init: &ConstExpr) -> &mut Self {
+        self.bytes.push(0x40);
+        self.bytes.push(0x00);
+        table_type.encode(&mut self.bytes);
+        init.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for TableSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl Section for TableSection {
+    fn id(&self) -> u8 {
+        SectionId::Table.into()
+    }
+}
+
+/// A table's type.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub struct TableType {
+    /// The table's element type.
+    pub element_type: RefType,
+    /// Minimum size, in elements, of this table
+    pub minimum: u32,
+    /// Maximum size, in elements, of this table
+    pub maximum: Option<u32>,
+}
+
+impl Encode for TableType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        let mut flags = 0;
+        if self.maximum.is_some() {
+            flags |= 0b001;
+        }
+
+        self.element_type.encode(sink);
+        sink.push(flags);
+        self.minimum.encode(sink);
+
+        if let Some(max) = self.maximum {
+            max.encode(sink);
+        }
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/tags.rs b/third_party/rust/wasm-encoder/src/core/tags.rs
new file mode 100644
index 0000000000..413055f2af
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/tags.rs
@@ -0,0 +1,85 @@
+use crate::{encode_section, Encode, Section, SectionId};
+
+/// An encoder for the tag section.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{Module, TagSection, TagType, TagKind};
+///
+/// let mut tags = TagSection::new();
+/// tags.tag(TagType {
+///     kind: TagKind::Exception,
+///     func_type_idx: 0,
+/// });
+///
+/// let mut module = Module::new();
+/// module.section(&tags);
+///
+/// let wasm_bytes = module.finish();
+/// ```
+#[derive(Clone, Default, Debug)]
+pub struct TagSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl TagSection {
+    /// Create a new tag section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of tags in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define a tag.
+    pub fn tag(&mut self, tag_type: TagType) -> &mut Self {
+        tag_type.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for TagSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl Section for TagSection {
+    fn id(&self) -> u8 {
+        SectionId::Tag.into()
+    }
+}
+
+/// Represents a tag kind.
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum TagKind {
+    /// The tag is an exception type.
+    Exception = 0x0,
+}
+
+/// A tag's type.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct TagType {
+    /// The kind of tag
+    pub kind: TagKind,
+    /// The function type this tag uses
+    pub func_type_idx: u32,
+}
+
+impl Encode for TagType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        sink.push(self.kind as u8);
+        self.func_type_idx.encode(sink);
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/core/types.rs b/third_party/rust/wasm-encoder/src/core/types.rs
new file mode 100644
index 0000000000..d21dbbc960
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/core/types.rs
@@ -0,0 +1,191 @@
+use crate::{encode_section, Encode, Section, SectionId};
+
+/// The type of a core WebAssembly value.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Ord, PartialOrd)]
+pub enum ValType {
+    /// The `i32` type.
+    I32,
+    /// The `i64` type.
+    I64,
+    /// The `f32` type.
+    F32,
+    /// The `f64` type.
+    F64,
+    /// The `v128` type.
+    ///
+    /// Part of the SIMD proposal.
+    V128,
+    /// A reference type.
+    ///
+    /// The `funcref` and `externref` type fall into this category and the full
+    /// generalization here is due to the implementation of the
+    /// function-references proposal.
+    Ref(RefType),
+}
+
+impl ValType {
+    /// Alias for the `funcref` type in WebAssembly
+    pub const FUNCREF: ValType = ValType::Ref(RefType::FUNCREF);
+    /// Alias for the `externref` type in WebAssembly
+    pub const EXTERNREF: ValType = ValType::Ref(RefType::EXTERNREF);
+}
+
+impl Encode for ValType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            ValType::I32 => sink.push(0x7F),
+            ValType::I64 => sink.push(0x7E),
+            ValType::F32 => sink.push(0x7D),
+            ValType::F64 => sink.push(0x7C),
+            ValType::V128 => sink.push(0x7B),
+            ValType::Ref(rt) => rt.encode(sink),
+        }
+    }
+}
+
+/// A reference type.
+///
+/// This is largely part of the function references proposal for WebAssembly but
+/// additionally is used by the `funcref` and `externref` types. The full
+/// generality of this type is only exercised with function-references.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Ord, PartialOrd)]
+#[allow(missing_docs)]
+pub struct RefType {
+    pub nullable: bool,
+    pub heap_type: HeapType,
+}
+
+impl RefType {
+    /// Alias for the `funcref` type in WebAssembly
+    pub const FUNCREF: RefType = RefType {
+        nullable: true,
+        heap_type: HeapType::Func,
+    };
+
+    /// Alias for the `externref` type in WebAssembly
+    pub const EXTERNREF: RefType = RefType {
+        nullable: true,
+        heap_type: HeapType::Extern,
+    };
+}
+
+impl Encode for RefType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        if self.nullable {
+            // Favor the original encodings of `funcref` and `externref` where
+            // possible
+            match self.heap_type {
+                HeapType::Func => return sink.push(0x70),
+                HeapType::Extern => return sink.push(0x6f),
+                _ => {}
+            }
+        }
+
+        if self.nullable {
+            sink.push(0x6C);
+        } else {
+            sink.push(0x6B);
+        }
+        self.heap_type.encode(sink);
+    }
+}
+
+impl From<RefType> for ValType {
+    fn from(ty: RefType) -> ValType {
+        ValType::Ref(ty)
+    }
+}
+
+/// Part of the function references proposal.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Ord, PartialOrd)]
+pub enum HeapType {
+    /// A function reference. When nullable, equivalent to `funcref`
+    Func,
+    /// An extern reference. When nullable, equivalent to `externref`
+    Extern,
+    /// A reference to a particular index in a table.
+    TypedFunc(u32),
+}
+
+impl Encode for HeapType {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            HeapType::Func => sink.push(0x70),
+            HeapType::Extern => sink.push(0x6F),
+            // Note that this is encoded as a signed type rather than unsigned
+            // as it's decoded as an s33
+            HeapType::TypedFunc(i) => i64::from(*i).encode(sink),
+        }
+    }
+}
+
+/// An encoder for the type section of WebAssembly modules.
+///
+/// # Example
+///
+/// ```rust
+/// use wasm_encoder::{Module, TypeSection, ValType};
+///
+/// let mut types = TypeSection::new();
+///
+/// types.function([ValType::I32, ValType::I32], [ValType::I64]);
+///
+/// let mut module = Module::new();
+/// module.section(&types);
+///
+/// let bytes = module.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct TypeSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl TypeSection {
+    /// Create a new module type section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of types in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define a function type in this type section.
+    pub fn function<P, R>(&mut self, params: P, results: R) -> &mut Self
+    where
+        P: IntoIterator<Item = ValType>,
+        P::IntoIter: ExactSizeIterator,
+        R: IntoIterator<Item = ValType>,
+        R::IntoIter: ExactSizeIterator,
+    {
+        let params = params.into_iter();
+        let results = results.into_iter();
+
+        self.bytes.push(0x60);
+        params.len().encode(&mut self.bytes);
+        params.for_each(|p| p.encode(&mut self.bytes));
+        results.len().encode(&mut self.bytes);
+        results.for_each(|p| p.encode(&mut self.bytes));
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for TypeSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl Section for TypeSection {
+    fn id(&self) -> u8 {
+        SectionId::Type.into()
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/lib.rs b/third_party/rust/wasm-encoder/src/lib.rs
new file mode 100644
index 0000000000..3f36562508
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/lib.rs
@@ -0,0 +1,188 @@
+//! A WebAssembly encoder.
+//!
+//! The main builder is the [`Module`]. You can build a section with a
+//! section-specific builder, like [`TypeSection`] or [`ImportSection`], and
+//! then add it to the module with [`Module::section`]. When you are finished
+//! building the module, call either [`Module::as_slice`] or [`Module::finish`]
+//! to get the encoded bytes. The former gives a shared reference to the
+//! underlying bytes as a slice, while the latter gives you ownership of them as
+//! a vector.
+//!
+//! # Example
+//!
+//! If we wanted to build this module:
+//!
+//! ```wasm
+//! (module
+//!   (type (func (param i32 i32) (result i32)))
+//!   (func (type 0)
+//!     local.get 0
+//!     local.get 1
+//!     i32.add)
+//!   (export "f" (func 0)))
+//! ```
+//!
+//! then we would do this:
+//!
+//! ```
+//! use wasm_encoder::{
+//!     CodeSection, ExportKind, ExportSection, Function, FunctionSection, Instruction,
+//!     Module, TypeSection, ValType,
+//! };
+//!
+//! let mut module = Module::new();
+//!
+//! // Encode the type section.
+//! let mut types = TypeSection::new();
+//! let params = vec![ValType::I32, ValType::I32];
+//! let results = vec![ValType::I32];
+//! types.function(params, results);
+//! module.section(&types);
+//!
+//! // Encode the function section.
+//! let mut functions = FunctionSection::new();
+//! let type_index = 0;
+//! functions.function(type_index);
+//! module.section(&functions);
+//!
+//! // Encode the export section.
+//! let mut exports = ExportSection::new();
+//! exports.export("f", ExportKind::Func, 0);
+//! module.section(&exports);
+//!
+//! // Encode the code section.
+//! let mut codes = CodeSection::new();
+//! let locals = vec![];
+//! let mut f = Function::new(locals);
+//! f.instruction(&Instruction::LocalGet(0));
+//! f.instruction(&Instruction::LocalGet(1));
+//! f.instruction(&Instruction::I32Add);
+//! f.instruction(&Instruction::End);
+//! codes.function(&f);
+//! module.section(&codes);
+//!
+//! // Extract the encoded Wasm bytes for this module.
+//! let wasm_bytes = module.finish();
+//!
+//! // We generated a valid Wasm module!
+//! assert!(wasmparser::validate(&wasm_bytes).is_ok());
+//! ```
+
+#![deny(missing_docs, missing_debug_implementations)]
+
+mod component;
+mod core;
+mod raw;
+
+pub use self::component::*;
+pub use self::core::*;
+pub use self::raw::*;
+
+/// Implemented by types that can be encoded into a byte sink.
+pub trait Encode {
+    /// Encode the type into the given byte sink.
+    fn encode(&self, sink: &mut Vec<u8>);
+}
+
+impl<T: Encode + ?Sized> Encode for &'_ T {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        T::encode(self, sink)
+    }
+}
+
+impl<T: Encode> Encode for [T] {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.len().encode(sink);
+        for item in self {
+            item.encode(sink);
+        }
+    }
+}
+
+impl Encode for [u8] {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.len().encode(sink);
+        sink.extend(self);
+    }
+}
+
+impl Encode for str {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.len().encode(sink);
+        sink.extend_from_slice(self.as_bytes());
+    }
+}
+
+impl Encode for usize {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        assert!(*self <= u32::max_value() as usize);
+        (*self as u32).encode(sink)
+    }
+}
+
+impl Encode for u32 {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        leb128::write::unsigned(sink, (*self).into()).unwrap();
+    }
+}
+
+impl Encode for i32 {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        leb128::write::signed(sink, (*self).into()).unwrap();
+    }
+}
+
+impl Encode for u64 {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        leb128::write::unsigned(sink, *self).unwrap();
+    }
+}
+
+impl Encode for i64 {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        leb128::write::signed(sink, *self).unwrap();
+    }
+}
+
+impl<T> Encode for Option<T>
+where
+    T: Encode,
+{
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Some(v) => {
+                sink.push(0x01);
+                v.encode(sink);
+            }
+            None => sink.push(0x00),
+        }
+    }
+}
+
+fn encoding_size(n: u32) -> usize {
+    let mut buf = [0u8; 5];
+    leb128::write::unsigned(&mut &mut buf[..], n.into()).unwrap()
+}
+
+fn encode_section(sink: &mut Vec<u8>, count: u32, bytes: &[u8]) {
+    (encoding_size(count) + bytes.len()).encode(sink);
+    count.encode(sink);
+    sink.extend(bytes);
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn it_encodes_an_empty_module() {
+        let bytes = Module::new().finish();
+        assert_eq!(bytes, [0x00, b'a', b's', b'm', 0x01, 0x00, 0x00, 0x00]);
+    }
+
+    #[test]
+    fn it_encodes_an_empty_component() {
+        let bytes = Component::new().finish();
+        assert_eq!(bytes, [0x00, b'a', b's', b'm', 0x0c, 0x00, 0x01, 0x00]);
+    }
+}
diff --git a/third_party/rust/wasm-encoder/src/raw.rs b/third_party/rust/wasm-encoder/src/raw.rs
new file mode 100644
index 0000000000..a1323ca88e
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/raw.rs
@@ -0,0 +1,30 @@
+use crate::{ComponentSection, Encode, Section};
+
+/// A section made up of uninterpreted, raw bytes.
+///
+/// Allows you to splat any data into a module or component.
+#[derive(Clone, Copy, Debug)]
+pub struct RawSection<'a> {
+    /// The id for this section.
+    pub id: u8,
+    /// The raw data for this section.
+    pub data: &'a [u8],
+}
+
+impl Encode for RawSection<'_> {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.data.encode(sink);
+    }
+}
+
+impl Section for RawSection<'_> {
+    fn id(&self) -> u8 {
+        self.id
+    }
+}
+
+impl ComponentSection for RawSection<'_> {
+    fn id(&self) -> u8 {
+        self.id
+    }
+}