Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

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

8 files changed, 2056 insertions, 0 deletions

diff --git a/compiler/rustc_serialize/Cargo.toml b/compiler/rustc_serialize/Cargo.toml
new file mode 100644
index 000000000..dbc5c1519
--- /dev/null
+++ b/compiler/rustc_serialize/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "rustc_serialize"
+version = "0.0.0"
+edition = "2021"
+
+[dependencies]
+indexmap = "1.9.1"
+smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
+
+[dev-dependencies]
+rustc_macros = { path = "../rustc_macros" }
diff --git a/compiler/rustc_serialize/src/collection_impls.rs b/compiler/rustc_serialize/src/collection_impls.rs
new file mode 100644
index 000000000..5e53f0b10
--- /dev/null
+++ b/compiler/rustc_serialize/src/collection_impls.rs
@@ -0,0 +1,267 @@
+//! Implementations of serialization for structures found in liballoc
+
+use std::hash::{BuildHasher, Hash};
+
+use crate::{Decodable, Decoder, Encodable, Encoder};
+use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet, LinkedList, VecDeque};
+use std::rc::Rc;
+use std::sync::Arc;
+
+use smallvec::{Array, SmallVec};
+
+impl<S: Encoder, A: Array<Item: Encodable<S>>> Encodable<S> for SmallVec<A> {
+    fn encode(&self, s: &mut S) {
+        let slice: &[A::Item] = self;
+        slice.encode(s);
+    }
+}
+
+impl<D: Decoder, A: Array<Item: Decodable<D>>> Decodable<D> for SmallVec<A> {
+    fn decode(d: &mut D) -> SmallVec<A> {
+        let len = d.read_usize();
+        (0..len).map(|_| Decodable::decode(d)).collect()
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for LinkedList<T> {
+    fn encode(&self, s: &mut S) {
+        s.emit_usize(self.len());
+        for e in self.iter() {
+            e.encode(s);
+        }
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for LinkedList<T> {
+    fn decode(d: &mut D) -> LinkedList<T> {
+        let len = d.read_usize();
+        (0..len).map(|_| Decodable::decode(d)).collect()
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for VecDeque<T> {
+    fn encode(&self, s: &mut S) {
+        s.emit_usize(self.len());
+        for e in self.iter() {
+            e.encode(s);
+        }
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for VecDeque<T> {
+    fn decode(d: &mut D) -> VecDeque<T> {
+        let len = d.read_usize();
+        (0..len).map(|_| Decodable::decode(d)).collect()
+    }
+}
+
+impl<S: Encoder, K, V> Encodable<S> for BTreeMap<K, V>
+where
+    K: Encodable<S> + PartialEq + Ord,
+    V: Encodable<S>,
+{
+    fn encode(&self, e: &mut S) {
+        e.emit_usize(self.len());
+        for (key, val) in self.iter() {
+            key.encode(e);
+            val.encode(e);
+        }
+    }
+}
+
+impl<D: Decoder, K, V> Decodable<D> for BTreeMap<K, V>
+where
+    K: Decodable<D> + PartialEq + Ord,
+    V: Decodable<D>,
+{
+    fn decode(d: &mut D) -> BTreeMap<K, V> {
+        let len = d.read_usize();
+        let mut map = BTreeMap::new();
+        for _ in 0..len {
+            let key = Decodable::decode(d);
+            let val = Decodable::decode(d);
+            map.insert(key, val);
+        }
+        map
+    }
+}
+
+impl<S: Encoder, T> Encodable<S> for BTreeSet<T>
+where
+    T: Encodable<S> + PartialEq + Ord,
+{
+    fn encode(&self, s: &mut S) {
+        s.emit_usize(self.len());
+        for e in self.iter() {
+            e.encode(s);
+        }
+    }
+}
+
+impl<D: Decoder, T> Decodable<D> for BTreeSet<T>
+where
+    T: Decodable<D> + PartialEq + Ord,
+{
+    fn decode(d: &mut D) -> BTreeSet<T> {
+        let len = d.read_usize();
+        let mut set = BTreeSet::new();
+        for _ in 0..len {
+            set.insert(Decodable::decode(d));
+        }
+        set
+    }
+}
+
+impl<E: Encoder, K, V, S> Encodable<E> for HashMap<K, V, S>
+where
+    K: Encodable<E> + Eq,
+    V: Encodable<E>,
+    S: BuildHasher,
+{
+    fn encode(&self, e: &mut E) {
+        e.emit_usize(self.len());
+        for (key, val) in self.iter() {
+            key.encode(e);
+            val.encode(e);
+        }
+    }
+}
+
+impl<D: Decoder, K, V, S> Decodable<D> for HashMap<K, V, S>
+where
+    K: Decodable<D> + Hash + Eq,
+    V: Decodable<D>,
+    S: BuildHasher + Default,
+{
+    fn decode(d: &mut D) -> HashMap<K, V, S> {
+        let len = d.read_usize();
+        let state = Default::default();
+        let mut map = HashMap::with_capacity_and_hasher(len, state);
+        for _ in 0..len {
+            let key = Decodable::decode(d);
+            let val = Decodable::decode(d);
+            map.insert(key, val);
+        }
+        map
+    }
+}
+
+impl<E: Encoder, T, S> Encodable<E> for HashSet<T, S>
+where
+    T: Encodable<E> + Eq,
+    S: BuildHasher,
+{
+    fn encode(&self, s: &mut E) {
+        s.emit_usize(self.len());
+        for e in self.iter() {
+            e.encode(s);
+        }
+    }
+}
+
+impl<D: Decoder, T, S> Decodable<D> for HashSet<T, S>
+where
+    T: Decodable<D> + Hash + Eq,
+    S: BuildHasher + Default,
+{
+    fn decode(d: &mut D) -> HashSet<T, S> {
+        let len = d.read_usize();
+        let state = Default::default();
+        let mut set = HashSet::with_capacity_and_hasher(len, state);
+        for _ in 0..len {
+            set.insert(Decodable::decode(d));
+        }
+        set
+    }
+}
+
+impl<E: Encoder, K, V, S> Encodable<E> for indexmap::IndexMap<K, V, S>
+where
+    K: Encodable<E> + Hash + Eq,
+    V: Encodable<E>,
+    S: BuildHasher,
+{
+    fn encode(&self, e: &mut E) {
+        e.emit_usize(self.len());
+        for (key, val) in self.iter() {
+            key.encode(e);
+            val.encode(e);
+        }
+    }
+}
+
+impl<D: Decoder, K, V, S> Decodable<D> for indexmap::IndexMap<K, V, S>
+where
+    K: Decodable<D> + Hash + Eq,
+    V: Decodable<D>,
+    S: BuildHasher + Default,
+{
+    fn decode(d: &mut D) -> indexmap::IndexMap<K, V, S> {
+        let len = d.read_usize();
+        let state = Default::default();
+        let mut map = indexmap::IndexMap::with_capacity_and_hasher(len, state);
+        for _ in 0..len {
+            let key = Decodable::decode(d);
+            let val = Decodable::decode(d);
+            map.insert(key, val);
+        }
+        map
+    }
+}
+
+impl<E: Encoder, T, S> Encodable<E> for indexmap::IndexSet<T, S>
+where
+    T: Encodable<E> + Hash + Eq,
+    S: BuildHasher,
+{
+    fn encode(&self, s: &mut E) {
+        s.emit_usize(self.len());
+        for e in self.iter() {
+            e.encode(s);
+        }
+    }
+}
+
+impl<D: Decoder, T, S> Decodable<D> for indexmap::IndexSet<T, S>
+where
+    T: Decodable<D> + Hash + Eq,
+    S: BuildHasher + Default,
+{
+    fn decode(d: &mut D) -> indexmap::IndexSet<T, S> {
+        let len = d.read_usize();
+        let state = Default::default();
+        let mut set = indexmap::IndexSet::with_capacity_and_hasher(len, state);
+        for _ in 0..len {
+            set.insert(Decodable::decode(d));
+        }
+        set
+    }
+}
+
+impl<E: Encoder, T: Encodable<E>> Encodable<E> for Rc<[T]> {
+    fn encode(&self, s: &mut E) {
+        let slice: &[T] = self;
+        slice.encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Rc<[T]> {
+    fn decode(d: &mut D) -> Rc<[T]> {
+        let vec: Vec<T> = Decodable::decode(d);
+        vec.into()
+    }
+}
+
+impl<E: Encoder, T: Encodable<E>> Encodable<E> for Arc<[T]> {
+    fn encode(&self, s: &mut E) {
+        let slice: &[T] = self;
+        slice.encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Arc<[T]> {
+    fn decode(d: &mut D) -> Arc<[T]> {
+        let vec: Vec<T> = Decodable::decode(d);
+        vec.into()
+    }
+}
diff --git a/compiler/rustc_serialize/src/leb128.rs b/compiler/rustc_serialize/src/leb128.rs
new file mode 100644
index 000000000..08b3c0542
--- /dev/null
+++ b/compiler/rustc_serialize/src/leb128.rs
@@ -0,0 +1,163 @@
+#![macro_use]
+
+macro_rules! max_leb128_len {
+    ($int_ty:ty) => {
+        // The longest LEB128 encoding for an integer uses 7 bits per byte.
+        (std::mem::size_of::<$int_ty>() * 8 + 6) / 7
+    };
+}
+
+// Returns the longest LEB128 encoding of all supported integer types.
+pub const fn max_leb128_len() -> usize {
+    max_leb128_len!(u128)
+}
+
+macro_rules! impl_write_unsigned_leb128 {
+    ($fn_name:ident, $int_ty:ty) => {
+        #[inline]
+        pub fn $fn_name(
+            out: &mut [::std::mem::MaybeUninit<u8>; max_leb128_len!($int_ty)],
+            mut value: $int_ty,
+        ) -> &[u8] {
+            let mut i = 0;
+
+            loop {
+                if value < 0x80 {
+                    unsafe {
+                        *out.get_unchecked_mut(i).as_mut_ptr() = value as u8;
+                    }
+
+                    i += 1;
+                    break;
+                } else {
+                    unsafe {
+                        *out.get_unchecked_mut(i).as_mut_ptr() = ((value & 0x7f) | 0x80) as u8;
+                    }
+
+                    value >>= 7;
+                    i += 1;
+                }
+            }
+
+            unsafe { ::std::mem::MaybeUninit::slice_assume_init_ref(&out.get_unchecked(..i)) }
+        }
+    };
+}
+
+impl_write_unsigned_leb128!(write_u16_leb128, u16);
+impl_write_unsigned_leb128!(write_u32_leb128, u32);
+impl_write_unsigned_leb128!(write_u64_leb128, u64);
+impl_write_unsigned_leb128!(write_u128_leb128, u128);
+impl_write_unsigned_leb128!(write_usize_leb128, usize);
+
+macro_rules! impl_read_unsigned_leb128 {
+    ($fn_name:ident, $int_ty:ty) => {
+        #[inline]
+        pub fn $fn_name(slice: &[u8], position: &mut usize) -> $int_ty {
+            // The first iteration of this loop is unpeeled. This is a
+            // performance win because this code is hot and integer values less
+            // than 128 are very common, typically occurring 50-80% or more of
+            // the time, even for u64 and u128.
+            let byte = slice[*position];
+            *position += 1;
+            if (byte & 0x80) == 0 {
+                return byte as $int_ty;
+            }
+            let mut result = (byte & 0x7F) as $int_ty;
+            let mut shift = 7;
+            loop {
+                let byte = slice[*position];
+                *position += 1;
+                if (byte & 0x80) == 0 {
+                    result |= (byte as $int_ty) << shift;
+                    return result;
+                } else {
+                    result |= ((byte & 0x7F) as $int_ty) << shift;
+                }
+                shift += 7;
+            }
+        }
+    };
+}
+
+impl_read_unsigned_leb128!(read_u16_leb128, u16);
+impl_read_unsigned_leb128!(read_u32_leb128, u32);
+impl_read_unsigned_leb128!(read_u64_leb128, u64);
+impl_read_unsigned_leb128!(read_u128_leb128, u128);
+impl_read_unsigned_leb128!(read_usize_leb128, usize);
+
+macro_rules! impl_write_signed_leb128 {
+    ($fn_name:ident, $int_ty:ty) => {
+        #[inline]
+        pub fn $fn_name(
+            out: &mut [::std::mem::MaybeUninit<u8>; max_leb128_len!($int_ty)],
+            mut value: $int_ty,
+        ) -> &[u8] {
+            let mut i = 0;
+
+            loop {
+                let mut byte = (value as u8) & 0x7f;
+                value >>= 7;
+                let more = !(((value == 0) && ((byte & 0x40) == 0))
+                    || ((value == -1) && ((byte & 0x40) != 0)));
+
+                if more {
+                    byte |= 0x80; // Mark this byte to show that more bytes will follow.
+                }
+
+                unsafe {
+                    *out.get_unchecked_mut(i).as_mut_ptr() = byte;
+                }
+
+                i += 1;
+
+                if !more {
+                    break;
+                }
+            }
+
+            unsafe { ::std::mem::MaybeUninit::slice_assume_init_ref(&out.get_unchecked(..i)) }
+        }
+    };
+}
+
+impl_write_signed_leb128!(write_i16_leb128, i16);
+impl_write_signed_leb128!(write_i32_leb128, i32);
+impl_write_signed_leb128!(write_i64_leb128, i64);
+impl_write_signed_leb128!(write_i128_leb128, i128);
+impl_write_signed_leb128!(write_isize_leb128, isize);
+
+macro_rules! impl_read_signed_leb128 {
+    ($fn_name:ident, $int_ty:ty) => {
+        #[inline]
+        pub fn $fn_name(slice: &[u8], position: &mut usize) -> $int_ty {
+            let mut result = 0;
+            let mut shift = 0;
+            let mut byte;
+
+            loop {
+                byte = slice[*position];
+                *position += 1;
+                result |= <$int_ty>::from(byte & 0x7F) << shift;
+                shift += 7;
+
+                if (byte & 0x80) == 0 {
+                    break;
+                }
+            }
+
+            if (shift < <$int_ty>::BITS) && ((byte & 0x40) != 0) {
+                // sign extend
+                result |= (!0 << shift);
+            }
+
+            result
+        }
+    };
+}
+
+impl_read_signed_leb128!(read_i16_leb128, i16);
+impl_read_signed_leb128!(read_i32_leb128, i32);
+impl_read_signed_leb128!(read_i64_leb128, i64);
+impl_read_signed_leb128!(read_i128_leb128, i128);
+impl_read_signed_leb128!(read_isize_leb128, isize);
diff --git a/compiler/rustc_serialize/src/lib.rs b/compiler/rustc_serialize/src/lib.rs
new file mode 100644
index 000000000..e606f4273
--- /dev/null
+++ b/compiler/rustc_serialize/src/lib.rs
@@ -0,0 +1,28 @@
+//! Support code for encoding and decoding types.
+
+/*
+Core encoding and decoding interfaces.
+*/
+
+#![doc(
+    html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/",
+    html_playground_url = "https://play.rust-lang.org/",
+    test(attr(allow(unused_variables), deny(warnings)))
+)]
+#![feature(never_type)]
+#![feature(associated_type_bounds)]
+#![feature(min_specialization)]
+#![feature(core_intrinsics)]
+#![feature(maybe_uninit_slice)]
+#![feature(let_else)]
+#![feature(new_uninit)]
+#![cfg_attr(test, feature(test))]
+#![allow(rustc::internal)]
+
+pub use self::serialize::{Decodable, Decoder, Encodable, Encoder};
+
+mod collection_impls;
+mod serialize;
+
+pub mod leb128;
+pub mod opaque;
diff --git a/compiler/rustc_serialize/src/opaque.rs b/compiler/rustc_serialize/src/opaque.rs
new file mode 100644
index 000000000..5c17ef6ac
--- /dev/null
+++ b/compiler/rustc_serialize/src/opaque.rs
@@ -0,0 +1,750 @@
+use crate::leb128::{self, max_leb128_len};
+use crate::serialize::{Decodable, Decoder, Encodable, Encoder};
+use std::convert::TryInto;
+use std::fs::File;
+use std::io::{self, Write};
+use std::mem::MaybeUninit;
+use std::path::Path;
+use std::ptr;
+
+// -----------------------------------------------------------------------------
+// Encoder
+// -----------------------------------------------------------------------------
+
+pub struct MemEncoder {
+    pub data: Vec<u8>,
+}
+
+impl MemEncoder {
+    pub fn new() -> MemEncoder {
+        MemEncoder { data: vec![] }
+    }
+
+    #[inline]
+    pub fn position(&self) -> usize {
+        self.data.len()
+    }
+
+    pub fn finish(self) -> Vec<u8> {
+        self.data
+    }
+}
+
+macro_rules! write_leb128 {
+    ($enc:expr, $value:expr, $int_ty:ty, $fun:ident) => {{
+        const MAX_ENCODED_LEN: usize = max_leb128_len!($int_ty);
+        let old_len = $enc.data.len();
+
+        if MAX_ENCODED_LEN > $enc.data.capacity() - old_len {
+            $enc.data.reserve(MAX_ENCODED_LEN);
+        }
+
+        // SAFETY: The above check and `reserve` ensures that there is enough
+        // room to write the encoded value to the vector's internal buffer.
+        unsafe {
+            let buf = &mut *($enc.data.as_mut_ptr().add(old_len)
+                as *mut [MaybeUninit<u8>; MAX_ENCODED_LEN]);
+            let encoded = leb128::$fun(buf, $value);
+            $enc.data.set_len(old_len + encoded.len());
+        }
+    }};
+}
+
+/// A byte that [cannot occur in UTF8 sequences][utf8]. Used to mark the end of a string.
+/// This way we can skip validation and still be relatively sure that deserialization
+/// did not desynchronize.
+///
+/// [utf8]: https://en.wikipedia.org/w/index.php?title=UTF-8&oldid=1058865525#Codepage_layout
+const STR_SENTINEL: u8 = 0xC1;
+
+impl Encoder for MemEncoder {
+    #[inline]
+    fn emit_usize(&mut self, v: usize) {
+        write_leb128!(self, v, usize, write_usize_leb128)
+    }
+
+    #[inline]
+    fn emit_u128(&mut self, v: u128) {
+        write_leb128!(self, v, u128, write_u128_leb128);
+    }
+
+    #[inline]
+    fn emit_u64(&mut self, v: u64) {
+        write_leb128!(self, v, u64, write_u64_leb128);
+    }
+
+    #[inline]
+    fn emit_u32(&mut self, v: u32) {
+        write_leb128!(self, v, u32, write_u32_leb128);
+    }
+
+    #[inline]
+    fn emit_u16(&mut self, v: u16) {
+        self.data.extend_from_slice(&v.to_le_bytes());
+    }
+
+    #[inline]
+    fn emit_u8(&mut self, v: u8) {
+        self.data.push(v);
+    }
+
+    #[inline]
+    fn emit_isize(&mut self, v: isize) {
+        write_leb128!(self, v, isize, write_isize_leb128)
+    }
+
+    #[inline]
+    fn emit_i128(&mut self, v: i128) {
+        write_leb128!(self, v, i128, write_i128_leb128)
+    }
+
+    #[inline]
+    fn emit_i64(&mut self, v: i64) {
+        write_leb128!(self, v, i64, write_i64_leb128)
+    }
+
+    #[inline]
+    fn emit_i32(&mut self, v: i32) {
+        write_leb128!(self, v, i32, write_i32_leb128)
+    }
+
+    #[inline]
+    fn emit_i16(&mut self, v: i16) {
+        self.data.extend_from_slice(&v.to_le_bytes());
+    }
+
+    #[inline]
+    fn emit_i8(&mut self, v: i8) {
+        self.emit_u8(v as u8);
+    }
+
+    #[inline]
+    fn emit_bool(&mut self, v: bool) {
+        self.emit_u8(if v { 1 } else { 0 });
+    }
+
+    #[inline]
+    fn emit_f64(&mut self, v: f64) {
+        let as_u64: u64 = v.to_bits();
+        self.emit_u64(as_u64);
+    }
+
+    #[inline]
+    fn emit_f32(&mut self, v: f32) {
+        let as_u32: u32 = v.to_bits();
+        self.emit_u32(as_u32);
+    }
+
+    #[inline]
+    fn emit_char(&mut self, v: char) {
+        self.emit_u32(v as u32);
+    }
+
+    #[inline]
+    fn emit_str(&mut self, v: &str) {
+        self.emit_usize(v.len());
+        self.emit_raw_bytes(v.as_bytes());
+        self.emit_u8(STR_SENTINEL);
+    }
+
+    #[inline]
+    fn emit_raw_bytes(&mut self, s: &[u8]) {
+        self.data.extend_from_slice(s);
+    }
+}
+
+pub type FileEncodeResult = Result<usize, io::Error>;
+
+// `FileEncoder` encodes data to file via fixed-size buffer.
+//
+// When encoding large amounts of data to a file, using `FileEncoder` may be
+// preferred over using `MemEncoder` to encode to a `Vec`, and then writing the
+// `Vec` to file, as the latter uses as much memory as there is encoded data,
+// while the former uses the fixed amount of memory allocated to the buffer.
+// `FileEncoder` also has the advantage of not needing to reallocate as data
+// is appended to it, but the disadvantage of requiring more error handling,
+// which has some runtime overhead.
+pub struct FileEncoder {
+    // The input buffer. For adequate performance, we need more control over
+    // buffering than `BufWriter` offers. If `BufWriter` ever offers a raw
+    // buffer access API, we can use it, and remove `buf` and `buffered`.
+    buf: Box<[MaybeUninit<u8>]>,
+    buffered: usize,
+    flushed: usize,
+    file: File,
+    // This is used to implement delayed error handling, as described in the
+    // comment on `trait Encoder`.
+    res: Result<(), io::Error>,
+}
+
+impl FileEncoder {
+    pub fn new<P: AsRef<Path>>(path: P) -> io::Result<Self> {
+        const DEFAULT_BUF_SIZE: usize = 8192;
+        FileEncoder::with_capacity(path, DEFAULT_BUF_SIZE)
+    }
+
+    pub fn with_capacity<P: AsRef<Path>>(path: P, capacity: usize) -> io::Result<Self> {
+        // Require capacity at least as large as the largest LEB128 encoding
+        // here, so that we don't have to check or handle this on every write.
+        assert!(capacity >= max_leb128_len());
+
+        // Require capacity small enough such that some capacity checks can be
+        // done using guaranteed non-overflowing add rather than sub, which
+        // shaves an instruction off those code paths (on x86 at least).
+        assert!(capacity <= usize::MAX - max_leb128_len());
+
+        let file = File::create(path)?;
+
+        Ok(FileEncoder {
+            buf: Box::new_uninit_slice(capacity),
+            buffered: 0,
+            flushed: 0,
+            file,
+            res: Ok(()),
+        })
+    }
+
+    #[inline]
+    pub fn position(&self) -> usize {
+        // Tracking position this way instead of having a `self.position` field
+        // means that we don't have to update the position on every write call.
+        self.flushed + self.buffered
+    }
+
+    pub fn flush(&mut self) {
+        // This is basically a copy of `BufWriter::flush`. If `BufWriter` ever
+        // offers a raw buffer access API, we can use it, and remove this.
+
+        /// Helper struct to ensure the buffer is updated after all the writes
+        /// are complete. It tracks the number of written bytes and drains them
+        /// all from the front of the buffer when dropped.
+        struct BufGuard<'a> {
+            buffer: &'a mut [u8],
+            encoder_buffered: &'a mut usize,
+            encoder_flushed: &'a mut usize,
+            flushed: usize,
+        }
+
+        impl<'a> BufGuard<'a> {
+            fn new(
+                buffer: &'a mut [u8],
+                encoder_buffered: &'a mut usize,
+                encoder_flushed: &'a mut usize,
+            ) -> Self {
+                assert_eq!(buffer.len(), *encoder_buffered);
+                Self { buffer, encoder_buffered, encoder_flushed, flushed: 0 }
+            }
+
+            /// The unwritten part of the buffer
+            fn remaining(&self) -> &[u8] {
+                &self.buffer[self.flushed..]
+            }
+
+            /// Flag some bytes as removed from the front of the buffer
+            fn consume(&mut self, amt: usize) {
+                self.flushed += amt;
+            }
+
+            /// true if all of the bytes have been written
+            fn done(&self) -> bool {
+                self.flushed >= *self.encoder_buffered
+            }
+        }
+
+        impl Drop for BufGuard<'_> {
+            fn drop(&mut self) {
+                if self.flushed > 0 {
+                    if self.done() {
+                        *self.encoder_flushed += *self.encoder_buffered;
+                        *self.encoder_buffered = 0;
+                    } else {
+                        self.buffer.copy_within(self.flushed.., 0);
+                        *self.encoder_flushed += self.flushed;
+                        *self.encoder_buffered -= self.flushed;
+                    }
+                }
+            }
+        }
+
+        // If we've already had an error, do nothing. It'll get reported after
+        // `finish` is called.
+        if self.res.is_err() {
+            return;
+        }
+
+        let mut guard = BufGuard::new(
+            unsafe { MaybeUninit::slice_assume_init_mut(&mut self.buf[..self.buffered]) },
+            &mut self.buffered,
+            &mut self.flushed,
+        );
+
+        while !guard.done() {
+            match self.file.write(guard.remaining()) {
+                Ok(0) => {
+                    self.res = Err(io::Error::new(
+                        io::ErrorKind::WriteZero,
+                        "failed to write the buffered data",
+                    ));
+                    return;
+                }
+                Ok(n) => guard.consume(n),
+                Err(ref e) if e.kind() == io::ErrorKind::Interrupted => {}
+                Err(e) => {
+                    self.res = Err(e);
+                    return;
+                }
+            }
+        }
+    }
+
+    pub fn file(&self) -> &File {
+        &self.file
+    }
+
+    #[inline]
+    fn capacity(&self) -> usize {
+        self.buf.len()
+    }
+
+    #[inline]
+    fn write_one(&mut self, value: u8) {
+        // We ensure this during `FileEncoder` construction.
+        debug_assert!(self.capacity() >= 1);
+
+        let mut buffered = self.buffered;
+
+        if std::intrinsics::unlikely(buffered >= self.capacity()) {
+            self.flush();
+            buffered = 0;
+        }
+
+        // SAFETY: The above check and `flush` ensures that there is enough
+        // room to write the input to the buffer.
+        unsafe {
+            *MaybeUninit::slice_as_mut_ptr(&mut self.buf).add(buffered) = value;
+        }
+
+        self.buffered = buffered + 1;
+    }
+
+    #[inline]
+    fn write_all(&mut self, buf: &[u8]) {
+        let capacity = self.capacity();
+        let buf_len = buf.len();
+
+        if std::intrinsics::likely(buf_len <= capacity) {
+            let mut buffered = self.buffered;
+
+            if std::intrinsics::unlikely(buf_len > capacity - buffered) {
+                self.flush();
+                buffered = 0;
+            }
+
+            // SAFETY: The above check and `flush` ensures that there is enough
+            // room to write the input to the buffer.
+            unsafe {
+                let src = buf.as_ptr();
+                let dst = MaybeUninit::slice_as_mut_ptr(&mut self.buf).add(buffered);
+                ptr::copy_nonoverlapping(src, dst, buf_len);
+            }
+
+            self.buffered = buffered + buf_len;
+        } else {
+            self.write_all_unbuffered(buf);
+        }
+    }
+
+    fn write_all_unbuffered(&mut self, mut buf: &[u8]) {
+        // If we've already had an error, do nothing. It'll get reported after
+        // `finish` is called.
+        if self.res.is_err() {
+            return;
+        }
+
+        if self.buffered > 0 {
+            self.flush();
+        }
+
+        // This is basically a copy of `Write::write_all` but also updates our
+        // `self.flushed`. It's necessary because `Write::write_all` does not
+        // return the number of bytes written when an error is encountered, and
+        // without that, we cannot accurately update `self.flushed` on error.
+        while !buf.is_empty() {
+            match self.file.write(buf) {
+                Ok(0) => {
+                    self.res = Err(io::Error::new(
+                        io::ErrorKind::WriteZero,
+                        "failed to write whole buffer",
+                    ));
+                    return;
+                }
+                Ok(n) => {
+                    buf = &buf[n..];
+                    self.flushed += n;
+                }
+                Err(ref e) if e.kind() == io::ErrorKind::Interrupted => {}
+                Err(e) => {
+                    self.res = Err(e);
+                    return;
+                }
+            }
+        }
+    }
+
+    pub fn finish(mut self) -> Result<usize, io::Error> {
+        self.flush();
+
+        let res = std::mem::replace(&mut self.res, Ok(()));
+        res.map(|()| self.position())
+    }
+}
+
+impl Drop for FileEncoder {
+    fn drop(&mut self) {
+        // Likely to be a no-op, because `finish` should have been called and
+        // it also flushes. But do it just in case.
+        let _result = self.flush();
+    }
+}
+
+macro_rules! file_encoder_write_leb128 {
+    ($enc:expr, $value:expr, $int_ty:ty, $fun:ident) => {{
+        const MAX_ENCODED_LEN: usize = max_leb128_len!($int_ty);
+
+        // We ensure this during `FileEncoder` construction.
+        debug_assert!($enc.capacity() >= MAX_ENCODED_LEN);
+
+        let mut buffered = $enc.buffered;
+
+        // This can't overflow. See assertion in `FileEncoder::with_capacity`.
+        if std::intrinsics::unlikely(buffered + MAX_ENCODED_LEN > $enc.capacity()) {
+            $enc.flush();
+            buffered = 0;
+        }
+
+        // SAFETY: The above check and flush ensures that there is enough
+        // room to write the encoded value to the buffer.
+        let buf = unsafe {
+            &mut *($enc.buf.as_mut_ptr().add(buffered) as *mut [MaybeUninit<u8>; MAX_ENCODED_LEN])
+        };
+
+        let encoded = leb128::$fun(buf, $value);
+        $enc.buffered = buffered + encoded.len();
+    }};
+}
+
+impl Encoder for FileEncoder {
+    #[inline]
+    fn emit_usize(&mut self, v: usize) {
+        file_encoder_write_leb128!(self, v, usize, write_usize_leb128)
+    }
+
+    #[inline]
+    fn emit_u128(&mut self, v: u128) {
+        file_encoder_write_leb128!(self, v, u128, write_u128_leb128)
+    }
+
+    #[inline]
+    fn emit_u64(&mut self, v: u64) {
+        file_encoder_write_leb128!(self, v, u64, write_u64_leb128)
+    }
+
+    #[inline]
+    fn emit_u32(&mut self, v: u32) {
+        file_encoder_write_leb128!(self, v, u32, write_u32_leb128)
+    }
+
+    #[inline]
+    fn emit_u16(&mut self, v: u16) {
+        self.write_all(&v.to_le_bytes());
+    }
+
+    #[inline]
+    fn emit_u8(&mut self, v: u8) {
+        self.write_one(v);
+    }
+
+    #[inline]
+    fn emit_isize(&mut self, v: isize) {
+        file_encoder_write_leb128!(self, v, isize, write_isize_leb128)
+    }
+
+    #[inline]
+    fn emit_i128(&mut self, v: i128) {
+        file_encoder_write_leb128!(self, v, i128, write_i128_leb128)
+    }
+
+    #[inline]
+    fn emit_i64(&mut self, v: i64) {
+        file_encoder_write_leb128!(self, v, i64, write_i64_leb128)
+    }
+
+    #[inline]
+    fn emit_i32(&mut self, v: i32) {
+        file_encoder_write_leb128!(self, v, i32, write_i32_leb128)
+    }
+
+    #[inline]
+    fn emit_i16(&mut self, v: i16) {
+        self.write_all(&v.to_le_bytes());
+    }
+
+    #[inline]
+    fn emit_i8(&mut self, v: i8) {
+        self.emit_u8(v as u8);
+    }
+
+    #[inline]
+    fn emit_bool(&mut self, v: bool) {
+        self.emit_u8(if v { 1 } else { 0 });
+    }
+
+    #[inline]
+    fn emit_f64(&mut self, v: f64) {
+        let as_u64: u64 = v.to_bits();
+        self.emit_u64(as_u64);
+    }
+
+    #[inline]
+    fn emit_f32(&mut self, v: f32) {
+        let as_u32: u32 = v.to_bits();
+        self.emit_u32(as_u32);
+    }
+
+    #[inline]
+    fn emit_char(&mut self, v: char) {
+        self.emit_u32(v as u32);
+    }
+
+    #[inline]
+    fn emit_str(&mut self, v: &str) {
+        self.emit_usize(v.len());
+        self.emit_raw_bytes(v.as_bytes());
+        self.emit_u8(STR_SENTINEL);
+    }
+
+    #[inline]
+    fn emit_raw_bytes(&mut self, s: &[u8]) {
+        self.write_all(s);
+    }
+}
+
+// -----------------------------------------------------------------------------
+// Decoder
+// -----------------------------------------------------------------------------
+
+pub struct MemDecoder<'a> {
+    pub data: &'a [u8],
+    position: usize,
+}
+
+impl<'a> MemDecoder<'a> {
+    #[inline]
+    pub fn new(data: &'a [u8], position: usize) -> MemDecoder<'a> {
+        MemDecoder { data, position }
+    }
+
+    #[inline]
+    pub fn position(&self) -> usize {
+        self.position
+    }
+
+    #[inline]
+    pub fn set_position(&mut self, pos: usize) {
+        self.position = pos
+    }
+
+    #[inline]
+    pub fn advance(&mut self, bytes: usize) {
+        self.position += bytes;
+    }
+}
+
+macro_rules! read_leb128 {
+    ($dec:expr, $fun:ident) => {{ leb128::$fun($dec.data, &mut $dec.position) }};
+}
+
+impl<'a> Decoder for MemDecoder<'a> {
+    #[inline]
+    fn read_u128(&mut self) -> u128 {
+        read_leb128!(self, read_u128_leb128)
+    }
+
+    #[inline]
+    fn read_u64(&mut self) -> u64 {
+        read_leb128!(self, read_u64_leb128)
+    }
+
+    #[inline]
+    fn read_u32(&mut self) -> u32 {
+        read_leb128!(self, read_u32_leb128)
+    }
+
+    #[inline]
+    fn read_u16(&mut self) -> u16 {
+        let bytes = [self.data[self.position], self.data[self.position + 1]];
+        let value = u16::from_le_bytes(bytes);
+        self.position += 2;
+        value
+    }
+
+    #[inline]
+    fn read_u8(&mut self) -> u8 {
+        let value = self.data[self.position];
+        self.position += 1;
+        value
+    }
+
+    #[inline]
+    fn read_usize(&mut self) -> usize {
+        read_leb128!(self, read_usize_leb128)
+    }
+
+    #[inline]
+    fn read_i128(&mut self) -> i128 {
+        read_leb128!(self, read_i128_leb128)
+    }
+
+    #[inline]
+    fn read_i64(&mut self) -> i64 {
+        read_leb128!(self, read_i64_leb128)
+    }
+
+    #[inline]
+    fn read_i32(&mut self) -> i32 {
+        read_leb128!(self, read_i32_leb128)
+    }
+
+    #[inline]
+    fn read_i16(&mut self) -> i16 {
+        let bytes = [self.data[self.position], self.data[self.position + 1]];
+        let value = i16::from_le_bytes(bytes);
+        self.position += 2;
+        value
+    }
+
+    #[inline]
+    fn read_i8(&mut self) -> i8 {
+        let value = self.data[self.position];
+        self.position += 1;
+        value as i8
+    }
+
+    #[inline]
+    fn read_isize(&mut self) -> isize {
+        read_leb128!(self, read_isize_leb128)
+    }
+
+    #[inline]
+    fn read_bool(&mut self) -> bool {
+        let value = self.read_u8();
+        value != 0
+    }
+
+    #[inline]
+    fn read_f64(&mut self) -> f64 {
+        let bits = self.read_u64();
+        f64::from_bits(bits)
+    }
+
+    #[inline]
+    fn read_f32(&mut self) -> f32 {
+        let bits = self.read_u32();
+        f32::from_bits(bits)
+    }
+
+    #[inline]
+    fn read_char(&mut self) -> char {
+        let bits = self.read_u32();
+        std::char::from_u32(bits).unwrap()
+    }
+
+    #[inline]
+    fn read_str(&mut self) -> &'a str {
+        let len = self.read_usize();
+        let sentinel = self.data[self.position + len];
+        assert!(sentinel == STR_SENTINEL);
+        let s = unsafe {
+            std::str::from_utf8_unchecked(&self.data[self.position..self.position + len])
+        };
+        self.position += len + 1;
+        s
+    }
+
+    #[inline]
+    fn read_raw_bytes(&mut self, bytes: usize) -> &'a [u8] {
+        let start = self.position;
+        self.position += bytes;
+        &self.data[start..self.position]
+    }
+}
+
+// Specializations for contiguous byte sequences follow. The default implementations for slices
+// encode and decode each element individually. This isn't necessary for `u8` slices when using
+// opaque encoders and decoders, because each `u8` is unchanged by encoding and decoding.
+// Therefore, we can use more efficient implementations that process the entire sequence at once.
+
+// Specialize encoding byte slices. This specialization also applies to encoding `Vec<u8>`s, etc.,
+// since the default implementations call `encode` on their slices internally.
+impl Encodable<MemEncoder> for [u8] {
+    fn encode(&self, e: &mut MemEncoder) {
+        Encoder::emit_usize(e, self.len());
+        e.emit_raw_bytes(self);
+    }
+}
+
+impl Encodable<FileEncoder> for [u8] {
+    fn encode(&self, e: &mut FileEncoder) {
+        Encoder::emit_usize(e, self.len());
+        e.emit_raw_bytes(self);
+    }
+}
+
+// Specialize decoding `Vec<u8>`. This specialization also applies to decoding `Box<[u8]>`s, etc.,
+// since the default implementations call `decode` to produce a `Vec<u8>` internally.
+impl<'a> Decodable<MemDecoder<'a>> for Vec<u8> {
+    fn decode(d: &mut MemDecoder<'a>) -> Self {
+        let len = Decoder::read_usize(d);
+        d.read_raw_bytes(len).to_owned()
+    }
+}
+
+// An integer that will always encode to 8 bytes.
+pub struct IntEncodedWithFixedSize(pub u64);
+
+impl IntEncodedWithFixedSize {
+    pub const ENCODED_SIZE: usize = 8;
+}
+
+impl Encodable<MemEncoder> for IntEncodedWithFixedSize {
+    #[inline]
+    fn encode(&self, e: &mut MemEncoder) {
+        let _start_pos = e.position();
+        e.emit_raw_bytes(&self.0.to_le_bytes());
+        let _end_pos = e.position();
+        debug_assert_eq!((_end_pos - _start_pos), IntEncodedWithFixedSize::ENCODED_SIZE);
+    }
+}
+
+impl Encodable<FileEncoder> for IntEncodedWithFixedSize {
+    #[inline]
+    fn encode(&self, e: &mut FileEncoder) {
+        let _start_pos = e.position();
+        e.emit_raw_bytes(&self.0.to_le_bytes());
+        let _end_pos = e.position();
+        debug_assert_eq!((_end_pos - _start_pos), IntEncodedWithFixedSize::ENCODED_SIZE);
+    }
+}
+
+impl<'a> Decodable<MemDecoder<'a>> for IntEncodedWithFixedSize {
+    #[inline]
+    fn decode(decoder: &mut MemDecoder<'a>) -> IntEncodedWithFixedSize {
+        let _start_pos = decoder.position();
+        let bytes = decoder.read_raw_bytes(IntEncodedWithFixedSize::ENCODED_SIZE);
+        let value = u64::from_le_bytes(bytes.try_into().unwrap());
+        let _end_pos = decoder.position();
+        debug_assert_eq!((_end_pos - _start_pos), IntEncodedWithFixedSize::ENCODED_SIZE);
+
+        IntEncodedWithFixedSize(value)
+    }
+}
diff --git a/compiler/rustc_serialize/src/serialize.rs b/compiler/rustc_serialize/src/serialize.rs
new file mode 100644
index 000000000..36585b8d7
--- /dev/null
+++ b/compiler/rustc_serialize/src/serialize.rs
@@ -0,0 +1,469 @@
+//! Support code for encoding and decoding types.
+
+/*
+Core encoding and decoding interfaces.
+*/
+
+use std::borrow::Cow;
+use std::cell::{Cell, RefCell};
+use std::marker::PhantomData;
+use std::path;
+use std::rc::Rc;
+use std::sync::Arc;
+
+/// A note about error handling.
+///
+/// Encoders may be fallible, but in practice failure is rare and there are so
+/// many nested calls that typical Rust error handling (via `Result` and `?`)
+/// is pervasive and has non-trivial cost. Instead, impls of this trait must
+/// implement a delayed error handling strategy. If a failure occurs, they
+/// should record this internally, and all subsequent encoding operations can
+/// be processed or ignored, whichever is appropriate. Then they should provide
+/// a `finish` method that finishes up encoding. If the encoder is fallible,
+/// `finish` should return a `Result` that indicates success or failure.
+pub trait Encoder {
+    // Primitive types:
+    fn emit_usize(&mut self, v: usize);
+    fn emit_u128(&mut self, v: u128);
+    fn emit_u64(&mut self, v: u64);
+    fn emit_u32(&mut self, v: u32);
+    fn emit_u16(&mut self, v: u16);
+    fn emit_u8(&mut self, v: u8);
+    fn emit_isize(&mut self, v: isize);
+    fn emit_i128(&mut self, v: i128);
+    fn emit_i64(&mut self, v: i64);
+    fn emit_i32(&mut self, v: i32);
+    fn emit_i16(&mut self, v: i16);
+    fn emit_i8(&mut self, v: i8);
+    fn emit_bool(&mut self, v: bool);
+    fn emit_f64(&mut self, v: f64);
+    fn emit_f32(&mut self, v: f32);
+    fn emit_char(&mut self, v: char);
+    fn emit_str(&mut self, v: &str);
+    fn emit_raw_bytes(&mut self, s: &[u8]);
+
+    // Convenience for the derive macro:
+    fn emit_enum_variant<F>(&mut self, v_id: usize, f: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        self.emit_usize(v_id);
+        f(self);
+    }
+
+    // We put the field index in a const generic to allow the emit_usize to be
+    // compiled into a more efficient form. In practice, the variant index is
+    // known at compile-time, and that knowledge allows much more efficient
+    // codegen than we'd otherwise get. LLVM isn't always able to make the
+    // optimization that would otherwise be necessary here, likely due to the
+    // multiple levels of inlining and const-prop that are needed.
+    #[inline]
+    fn emit_fieldless_enum_variant<const ID: usize>(&mut self) {
+        self.emit_usize(ID)
+    }
+}
+
+// Note: all the methods in this trait are infallible, which may be surprising.
+// They used to be fallible (i.e. return a `Result`) but many of the impls just
+// panicked when something went wrong, and for the cases that didn't the
+// top-level invocation would also just panic on failure. Switching to
+// infallibility made things faster and lots of code a little simpler and more
+// concise.
+pub trait Decoder {
+    // Primitive types:
+    fn read_usize(&mut self) -> usize;
+    fn read_u128(&mut self) -> u128;
+    fn read_u64(&mut self) -> u64;
+    fn read_u32(&mut self) -> u32;
+    fn read_u16(&mut self) -> u16;
+    fn read_u8(&mut self) -> u8;
+    fn read_isize(&mut self) -> isize;
+    fn read_i128(&mut self) -> i128;
+    fn read_i64(&mut self) -> i64;
+    fn read_i32(&mut self) -> i32;
+    fn read_i16(&mut self) -> i16;
+    fn read_i8(&mut self) -> i8;
+    fn read_bool(&mut self) -> bool;
+    fn read_f64(&mut self) -> f64;
+    fn read_f32(&mut self) -> f32;
+    fn read_char(&mut self) -> char;
+    fn read_str(&mut self) -> &str;
+    fn read_raw_bytes(&mut self, len: usize) -> &[u8];
+}
+
+/// Trait for types that can be serialized
+///
+/// This can be implemented using the `Encodable`, `TyEncodable` and
+/// `MetadataEncodable` macros.
+///
+/// * `Encodable` should be used in crates that don't depend on
+///   `rustc_middle`.
+/// * `MetadataEncodable` is used in `rustc_metadata` for types that contain
+///   `rustc_metadata::rmeta::Lazy`.
+/// * `TyEncodable` should be used for types that are only serialized in crate
+///   metadata or the incremental cache. This is most types in `rustc_middle`.
+pub trait Encodable<S: Encoder> {
+    fn encode(&self, s: &mut S);
+}
+
+/// Trait for types that can be deserialized
+///
+/// This can be implemented using the `Decodable`, `TyDecodable` and
+/// `MetadataDecodable` macros.
+///
+/// * `Decodable` should be used in crates that don't depend on
+///   `rustc_middle`.
+/// * `MetadataDecodable` is used in `rustc_metadata` for types that contain
+///   `rustc_metadata::rmeta::Lazy`.
+/// * `TyDecodable` should be used for types that are only serialized in crate
+///   metadata or the incremental cache. This is most types in `rustc_middle`.
+pub trait Decodable<D: Decoder>: Sized {
+    fn decode(d: &mut D) -> Self;
+}
+
+macro_rules! direct_serialize_impls {
+    ($($ty:ident $emit_method:ident $read_method:ident),*) => {
+        $(
+            impl<S: Encoder> Encodable<S> for $ty {
+                fn encode(&self, s: &mut S) {
+                    s.$emit_method(*self);
+                }
+            }
+
+            impl<D: Decoder> Decodable<D> for $ty {
+                fn decode(d: &mut D) -> $ty {
+                    d.$read_method()
+                }
+            }
+        )*
+    }
+}
+
+direct_serialize_impls! {
+    usize emit_usize read_usize,
+    u8 emit_u8 read_u8,
+    u16 emit_u16 read_u16,
+    u32 emit_u32 read_u32,
+    u64 emit_u64 read_u64,
+    u128 emit_u128 read_u128,
+
+    isize emit_isize read_isize,
+    i8 emit_i8 read_i8,
+    i16 emit_i16 read_i16,
+    i32 emit_i32 read_i32,
+    i64 emit_i64 read_i64,
+    i128 emit_i128 read_i128,
+
+    f32 emit_f32 read_f32,
+    f64 emit_f64 read_f64,
+    bool emit_bool read_bool,
+    char emit_char read_char
+}
+
+impl<S: Encoder, T: ?Sized> Encodable<S> for &T
+where
+    T: Encodable<S>,
+{
+    fn encode(&self, s: &mut S) {
+        (**self).encode(s)
+    }
+}
+
+impl<S: Encoder> Encodable<S> for ! {
+    fn encode(&self, _s: &mut S) {
+        unreachable!();
+    }
+}
+
+impl<D: Decoder> Decodable<D> for ! {
+    fn decode(_d: &mut D) -> ! {
+        unreachable!()
+    }
+}
+
+impl<S: Encoder> Encodable<S> for ::std::num::NonZeroU32 {
+    fn encode(&self, s: &mut S) {
+        s.emit_u32(self.get());
+    }
+}
+
+impl<D: Decoder> Decodable<D> for ::std::num::NonZeroU32 {
+    fn decode(d: &mut D) -> Self {
+        ::std::num::NonZeroU32::new(d.read_u32()).unwrap()
+    }
+}
+
+impl<S: Encoder> Encodable<S> for str {
+    fn encode(&self, s: &mut S) {
+        s.emit_str(self);
+    }
+}
+
+impl<S: Encoder> Encodable<S> for String {
+    fn encode(&self, s: &mut S) {
+        s.emit_str(&self[..]);
+    }
+}
+
+impl<D: Decoder> Decodable<D> for String {
+    fn decode(d: &mut D) -> String {
+        d.read_str().to_owned()
+    }
+}
+
+impl<S: Encoder> Encodable<S> for () {
+    fn encode(&self, _s: &mut S) {}
+}
+
+impl<D: Decoder> Decodable<D> for () {
+    fn decode(_: &mut D) -> () {}
+}
+
+impl<S: Encoder, T> Encodable<S> for PhantomData<T> {
+    fn encode(&self, _s: &mut S) {}
+}
+
+impl<D: Decoder, T> Decodable<D> for PhantomData<T> {
+    fn decode(_: &mut D) -> PhantomData<T> {
+        PhantomData
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Box<[T]> {
+    fn decode(d: &mut D) -> Box<[T]> {
+        let v: Vec<T> = Decodable::decode(d);
+        v.into_boxed_slice()
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for Rc<T> {
+    fn encode(&self, s: &mut S) {
+        (**self).encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Rc<T> {
+    fn decode(d: &mut D) -> Rc<T> {
+        Rc::new(Decodable::decode(d))
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for [T] {
+    default fn encode(&self, s: &mut S) {
+        s.emit_usize(self.len());
+        for e in self.iter() {
+            e.encode(s);
+        }
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for Vec<T> {
+    fn encode(&self, s: &mut S) {
+        let slice: &[T] = self;
+        slice.encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Vec<T> {
+    default fn decode(d: &mut D) -> Vec<T> {
+        let len = d.read_usize();
+        // SAFETY: we set the capacity in advance, only write elements, and
+        // only set the length at the end once the writing has succeeded.
+        let mut vec = Vec::with_capacity(len);
+        unsafe {
+            let ptr: *mut T = vec.as_mut_ptr();
+            for i in 0..len {
+                std::ptr::write(ptr.offset(i as isize), Decodable::decode(d));
+            }
+            vec.set_len(len);
+        }
+        vec
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>, const N: usize> Encodable<S> for [T; N] {
+    fn encode(&self, s: &mut S) {
+        let slice: &[T] = self;
+        slice.encode(s);
+    }
+}
+
+impl<D: Decoder, const N: usize> Decodable<D> for [u8; N] {
+    fn decode(d: &mut D) -> [u8; N] {
+        let len = d.read_usize();
+        assert!(len == N);
+        let mut v = [0u8; N];
+        for i in 0..len {
+            v[i] = Decodable::decode(d);
+        }
+        v
+    }
+}
+
+impl<'a, S: Encoder, T: Encodable<S>> Encodable<S> for Cow<'a, [T]>
+where
+    [T]: ToOwned<Owned = Vec<T>>,
+{
+    fn encode(&self, s: &mut S) {
+        let slice: &[T] = self;
+        slice.encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D> + ToOwned> Decodable<D> for Cow<'static, [T]>
+where
+    [T]: ToOwned<Owned = Vec<T>>,
+{
+    fn decode(d: &mut D) -> Cow<'static, [T]> {
+        let v: Vec<T> = Decodable::decode(d);
+        Cow::Owned(v)
+    }
+}
+
+impl<'a, S: Encoder> Encodable<S> for Cow<'a, str> {
+    fn encode(&self, s: &mut S) {
+        let val: &str = self;
+        val.encode(s)
+    }
+}
+
+impl<'a, D: Decoder> Decodable<D> for Cow<'a, str> {
+    fn decode(d: &mut D) -> Cow<'static, str> {
+        let v: String = Decodable::decode(d);
+        Cow::Owned(v)
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for Option<T> {
+    fn encode(&self, s: &mut S) {
+        match *self {
+            None => s.emit_enum_variant(0, |_| {}),
+            Some(ref v) => s.emit_enum_variant(1, |s| v.encode(s)),
+        }
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Option<T> {
+    fn decode(d: &mut D) -> Option<T> {
+        match d.read_usize() {
+            0 => None,
+            1 => Some(Decodable::decode(d)),
+            _ => panic!("Encountered invalid discriminant while decoding `Option`."),
+        }
+    }
+}
+
+impl<S: Encoder, T1: Encodable<S>, T2: Encodable<S>> Encodable<S> for Result<T1, T2> {
+    fn encode(&self, s: &mut S) {
+        match *self {
+            Ok(ref v) => s.emit_enum_variant(0, |s| v.encode(s)),
+            Err(ref v) => s.emit_enum_variant(1, |s| v.encode(s)),
+        }
+    }
+}
+
+impl<D: Decoder, T1: Decodable<D>, T2: Decodable<D>> Decodable<D> for Result<T1, T2> {
+    fn decode(d: &mut D) -> Result<T1, T2> {
+        match d.read_usize() {
+            0 => Ok(T1::decode(d)),
+            1 => Err(T2::decode(d)),
+            _ => panic!("Encountered invalid discriminant while decoding `Result`."),
+        }
+    }
+}
+
+macro_rules! peel {
+    ($name:ident, $($other:ident,)*) => (tuple! { $($other,)* })
+}
+
+macro_rules! tuple {
+    () => ();
+    ( $($name:ident,)+ ) => (
+        impl<D: Decoder, $($name: Decodable<D>),+> Decodable<D> for ($($name,)+) {
+            fn decode(d: &mut D) -> ($($name,)+) {
+                ($({ let element: $name = Decodable::decode(d); element },)+)
+            }
+        }
+        impl<S: Encoder, $($name: Encodable<S>),+> Encodable<S> for ($($name,)+) {
+            #[allow(non_snake_case)]
+            fn encode(&self, s: &mut S) {
+                let ($(ref $name,)+) = *self;
+                $($name.encode(s);)+
+            }
+        }
+        peel! { $($name,)+ }
+    )
+}
+
+tuple! { T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, }
+
+impl<S: Encoder> Encodable<S> for path::Path {
+    fn encode(&self, e: &mut S) {
+        self.to_str().unwrap().encode(e);
+    }
+}
+
+impl<S: Encoder> Encodable<S> for path::PathBuf {
+    fn encode(&self, e: &mut S) {
+        path::Path::encode(self, e);
+    }
+}
+
+impl<D: Decoder> Decodable<D> for path::PathBuf {
+    fn decode(d: &mut D) -> path::PathBuf {
+        let bytes: String = Decodable::decode(d);
+        path::PathBuf::from(bytes)
+    }
+}
+
+impl<S: Encoder, T: Encodable<S> + Copy> Encodable<S> for Cell<T> {
+    fn encode(&self, s: &mut S) {
+        self.get().encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D> + Copy> Decodable<D> for Cell<T> {
+    fn decode(d: &mut D) -> Cell<T> {
+        Cell::new(Decodable::decode(d))
+    }
+}
+
+// FIXME: #15036
+// Should use `try_borrow`, returning an
+// `encoder.error("attempting to Encode borrowed RefCell")`
+// from `encode` when `try_borrow` returns `None`.
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for RefCell<T> {
+    fn encode(&self, s: &mut S) {
+        self.borrow().encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for RefCell<T> {
+    fn decode(d: &mut D) -> RefCell<T> {
+        RefCell::new(Decodable::decode(d))
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for Arc<T> {
+    fn encode(&self, s: &mut S) {
+        (**self).encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Arc<T> {
+    fn decode(d: &mut D) -> Arc<T> {
+        Arc::new(Decodable::decode(d))
+    }
+}
+
+impl<S: Encoder, T: ?Sized + Encodable<S>> Encodable<S> for Box<T> {
+    fn encode(&self, s: &mut S) {
+        (**self).encode(s);
+    }
+}
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Box<T> {
+    fn decode(d: &mut D) -> Box<T> {
+        Box::new(Decodable::decode(d))
+    }
+}
diff --git a/compiler/rustc_serialize/tests/leb128.rs b/compiler/rustc_serialize/tests/leb128.rs
new file mode 100644
index 000000000..314c07db9
--- /dev/null
+++ b/compiler/rustc_serialize/tests/leb128.rs
@@ -0,0 +1,91 @@
+#![feature(maybe_uninit_slice)]
+#![feature(maybe_uninit_uninit_array)]
+
+use rustc_serialize::leb128::*;
+use std::mem::MaybeUninit;
+
+macro_rules! impl_test_unsigned_leb128 {
+    ($test_name:ident, $write_fn_name:ident, $read_fn_name:ident, $int_ty:ident) => {
+        #[test]
+        fn $test_name() {
+            // Test 256 evenly spaced values of integer range,
+            // integer max value, and some "random" numbers.
+            let mut values = Vec::new();
+
+            let increment = (1 as $int_ty) << ($int_ty::BITS - 8);
+            values.extend((0..256).map(|i| $int_ty::MIN + i * increment));
+
+            values.push($int_ty::MAX);
+
+            values.extend(
+                (-500..500).map(|i| (i as $int_ty).wrapping_mul(0x12345789ABCDEFu64 as $int_ty)),
+            );
+
+            let mut stream = Vec::new();
+
+            for &x in &values {
+                let mut buf = MaybeUninit::uninit_array();
+                stream.extend($write_fn_name(&mut buf, x));
+            }
+
+            let mut position = 0;
+            for &expected in &values {
+                let actual = $read_fn_name(&stream, &mut position);
+                assert_eq!(expected, actual);
+            }
+            assert_eq!(stream.len(), position);
+        }
+    };
+}
+
+impl_test_unsigned_leb128!(test_u16_leb128, write_u16_leb128, read_u16_leb128, u16);
+impl_test_unsigned_leb128!(test_u32_leb128, write_u32_leb128, read_u32_leb128, u32);
+impl_test_unsigned_leb128!(test_u64_leb128, write_u64_leb128, read_u64_leb128, u64);
+impl_test_unsigned_leb128!(test_u128_leb128, write_u128_leb128, read_u128_leb128, u128);
+impl_test_unsigned_leb128!(test_usize_leb128, write_usize_leb128, read_usize_leb128, usize);
+
+macro_rules! impl_test_signed_leb128 {
+    ($test_name:ident, $write_fn_name:ident, $read_fn_name:ident, $int_ty:ident) => {
+        #[test]
+        fn $test_name() {
+            // Test 256 evenly spaced values of integer range,
+            // integer max value, and some "random" numbers.
+            let mut values = Vec::new();
+
+            let mut value = $int_ty::MIN;
+            let increment = (1 as $int_ty) << ($int_ty::BITS - 8);
+
+            for _ in 0..256 {
+                values.push(value);
+                // The addition in the last loop iteration overflows.
+                value = value.wrapping_add(increment);
+            }
+
+            values.push($int_ty::MAX);
+
+            values.extend(
+                (-500..500).map(|i| (i as $int_ty).wrapping_mul(0x12345789ABCDEFi64 as $int_ty)),
+            );
+
+            let mut stream = Vec::new();
+
+            for &x in &values {
+                let mut buf = MaybeUninit::uninit_array();
+                stream.extend($write_fn_name(&mut buf, x));
+            }
+
+            let mut position = 0;
+            for &expected in &values {
+                let actual = $read_fn_name(&stream, &mut position);
+                assert_eq!(expected, actual);
+            }
+            assert_eq!(stream.len(), position);
+        }
+    };
+}
+
+impl_test_signed_leb128!(test_i16_leb128, write_i16_leb128, read_i16_leb128, i16);
+impl_test_signed_leb128!(test_i32_leb128, write_i32_leb128, read_i32_leb128, i32);
+impl_test_signed_leb128!(test_i64_leb128, write_i64_leb128, read_i64_leb128, i64);
+impl_test_signed_leb128!(test_i128_leb128, write_i128_leb128, read_i128_leb128, i128);
+impl_test_signed_leb128!(test_isize_leb128, write_isize_leb128, read_isize_leb128, isize);
diff --git a/compiler/rustc_serialize/tests/opaque.rs b/compiler/rustc_serialize/tests/opaque.rs
new file mode 100644
index 000000000..3a695d071
--- /dev/null
+++ b/compiler/rustc_serialize/tests/opaque.rs
@@ -0,0 +1,277 @@
+#![allow(rustc::internal)]
+
+use rustc_macros::{Decodable, Encodable};
+use rustc_serialize::opaque::{MemDecoder, MemEncoder};
+use rustc_serialize::{Decodable, Encodable};
+use std::fmt::Debug;
+
+#[derive(PartialEq, Clone, Debug, Encodable, Decodable)]
+struct Struct {
+    a: (),
+    b: u8,
+    c: u16,
+    d: u32,
+    e: u64,
+    f: usize,
+
+    g: i8,
+    h: i16,
+    i: i32,
+    j: i64,
+    k: isize,
+
+    l: char,
+    m: String,
+    n: f32,
+    o: f64,
+    p: bool,
+    q: Option<u32>,
+}
+
+fn check_round_trip<
+    T: Encodable<MemEncoder> + for<'a> Decodable<MemDecoder<'a>> + PartialEq + Debug,
+>(
+    values: Vec<T>,
+) {
+    let mut encoder = MemEncoder::new();
+    for value in &values {
+        Encodable::encode(value, &mut encoder);
+    }
+
+    let data = encoder.finish();
+    let mut decoder = MemDecoder::new(&data[..], 0);
+
+    for value in values {
+        let decoded = Decodable::decode(&mut decoder);
+        assert_eq!(value, decoded);
+    }
+}
+
+#[test]
+fn test_unit() {
+    check_round_trip(vec![(), (), (), ()]);
+}
+
+#[test]
+fn test_u8() {
+    let mut vec = vec![];
+    for i in u8::MIN..u8::MAX {
+        vec.push(i);
+    }
+    check_round_trip(vec);
+}
+
+#[test]
+fn test_u16() {
+    for i in u16::MIN..u16::MAX {
+        check_round_trip(vec![1, 2, 3, i, i, i]);
+    }
+}
+
+#[test]
+fn test_u32() {
+    check_round_trip(vec![1, 2, 3, u32::MIN, 0, 1, u32::MAX, 2, 1]);
+}
+
+#[test]
+fn test_u64() {
+    check_round_trip(vec![1, 2, 3, u64::MIN, 0, 1, u64::MAX, 2, 1]);
+}
+
+#[test]
+fn test_usize() {
+    check_round_trip(vec![1, 2, 3, usize::MIN, 0, 1, usize::MAX, 2, 1]);
+}
+
+#[test]
+fn test_i8() {
+    let mut vec = vec![];
+    for i in i8::MIN..i8::MAX {
+        vec.push(i);
+    }
+    check_round_trip(vec);
+}
+
+#[test]
+fn test_i16() {
+    for i in i16::MIN..i16::MAX {
+        check_round_trip(vec![-1, 2, -3, i, i, i, 2]);
+    }
+}
+
+#[test]
+fn test_i32() {
+    check_round_trip(vec![-1, 2, -3, i32::MIN, 0, 1, i32::MAX, 2, 1]);
+}
+
+#[test]
+fn test_i64() {
+    check_round_trip(vec![-1, 2, -3, i64::MIN, 0, 1, i64::MAX, 2, 1]);
+}
+
+#[test]
+fn test_isize() {
+    check_round_trip(vec![-1, 2, -3, isize::MIN, 0, 1, isize::MAX, 2, 1]);
+}
+
+#[test]
+fn test_bool() {
+    check_round_trip(vec![false, true, true, false, false]);
+}
+
+#[test]
+fn test_f32() {
+    let mut vec = vec![];
+    for i in -100..100 {
+        vec.push((i as f32) / 3.0);
+    }
+    check_round_trip(vec);
+}
+
+#[test]
+fn test_f64() {
+    let mut vec = vec![];
+    for i in -100..100 {
+        vec.push((i as f64) / 3.0);
+    }
+    check_round_trip(vec);
+}
+
+#[test]
+fn test_char() {
+    let vec = vec!['a', 'b', 'c', 'd', 'A', 'X', ' ', '#', 'Ö', 'Ä', 'µ', '€'];
+    check_round_trip(vec);
+}
+
+#[test]
+fn test_string() {
+    let vec = vec![
+        "abcbuÖeiovÄnameÜavmpßvmea€µsbpnvapeapmaebn".to_string(),
+        "abcbuÖganeiovÄnameÜavmpßvmea€µsbpnvapeapmaebn".to_string(),
+        "abcbuÖganeiovÄnameÜavmpßvmea€µsbpapmaebn".to_string(),
+        "abcbuÖganeiovÄnameÜavmpßvmeabpnvapeapmaebn".to_string(),
+        "abcbuÖganeiÄnameÜavmpßvmea€µsbpnvapeapmaebn".to_string(),
+        "abcbuÖganeiovÄnameÜavmpßvmea€µsbpmaebn".to_string(),
+        "abcbuÖganeiovÄnameÜavmpßvmea€µnvapeapmaebn".to_string(),
+    ];
+
+    check_round_trip(vec);
+}
+
+#[test]
+fn test_option() {
+    check_round_trip(vec![Some(-1i8)]);
+    check_round_trip(vec![Some(-2i16)]);
+    check_round_trip(vec![Some(-3i32)]);
+    check_round_trip(vec![Some(-4i64)]);
+    check_round_trip(vec![Some(-5isize)]);
+
+    let none_i8: Option<i8> = None;
+    check_round_trip(vec![none_i8]);
+
+    let none_i16: Option<i16> = None;
+    check_round_trip(vec![none_i16]);
+
+    let none_i32: Option<i32> = None;
+    check_round_trip(vec![none_i32]);
+
+    let none_i64: Option<i64> = None;
+    check_round_trip(vec![none_i64]);
+
+    let none_isize: Option<isize> = None;
+    check_round_trip(vec![none_isize]);
+}
+
+#[test]
+fn test_struct() {
+    check_round_trip(vec![Struct {
+        a: (),
+        b: 10,
+        c: 11,
+        d: 12,
+        e: 13,
+        f: 14,
+
+        g: 15,
+        h: 16,
+        i: 17,
+        j: 18,
+        k: 19,
+
+        l: 'x',
+        m: "abc".to_string(),
+        n: 20.5,
+        o: 21.5,
+        p: false,
+        q: None,
+    }]);
+
+    check_round_trip(vec![Struct {
+        a: (),
+        b: 101,
+        c: 111,
+        d: 121,
+        e: 131,
+        f: 141,
+
+        g: -15,
+        h: -16,
+        i: -17,
+        j: -18,
+        k: -19,
+
+        l: 'y',
+        m: "def".to_string(),
+        n: -20.5,
+        o: -21.5,
+        p: true,
+        q: Some(1234567),
+    }]);
+}
+
+#[derive(PartialEq, Clone, Debug, Encodable, Decodable)]
+enum Enum {
+    Variant1,
+    Variant2(usize, f32),
+    Variant3 { a: i32, b: char, c: bool },
+}
+
+#[test]
+fn test_enum() {
+    check_round_trip(vec![
+        Enum::Variant1,
+        Enum::Variant2(1, 2.5),
+        Enum::Variant3 { a: 3, b: 'b', c: false },
+        Enum::Variant3 { a: -4, b: 'f', c: true },
+    ]);
+}
+
+#[test]
+fn test_sequence() {
+    let mut vec = vec![];
+    for i in -100i64..100i64 {
+        vec.push(i * 100000);
+    }
+
+    check_round_trip(vec![vec]);
+}
+
+#[test]
+fn test_hash_map() {
+    use std::collections::HashMap;
+    let mut map = HashMap::new();
+    for i in -100i64..100i64 {
+        map.insert(i * 100000, i * 10000);
+    }
+
+    check_round_trip(vec![map]);
+}
+
+#[test]
+fn test_tuples() {
+    check_round_trip(vec![('x', (), false, 0.5f32)]);
+    check_round_trip(vec![(9i8, 10u16, 1.5f64)]);
+    check_round_trip(vec![(-12i16, 11u8, 12usize)]);
+    check_round_trip(vec![(1234567isize, 100000000000000u64, 99999999999999i64)]);
+    check_round_trip(vec![(String::new(), "some string".to_string())]);
+}