1 files changed, 418 insertions, 0 deletions
diff --git a/third_party/rust/cranelift-wasm/src/func_translator.rs b/third_party/rust/cranelift-wasm/src/func_translator.rs
new file mode 100644
index 0000000000..158271ab96
--- /dev/null
+++ b/third_party/rust/cranelift-wasm/src/func_translator.rs
@@ -0,0 +1,418 @@
+//! Stand-alone WebAssembly to Cranelift IR translator.
+//!
+//! This module defines the `FuncTranslator` type which can translate a single WebAssembly
+//! function to Cranelift IR guided by a `FuncEnvironment` which provides information about the
+//! WebAssembly module and the runtime environment.
+
+use crate::code_translator::{bitcast_arguments, translate_operator, wasm_param_types};
+use crate::environ::{FuncEnvironment, ReturnMode, WasmResult};
+use crate::state::FuncTranslationState;
+use crate::translation_utils::get_vmctx_value_label;
+use crate::wasm_unsupported;
+use core::convert::TryInto;
+use cranelift_codegen::entity::EntityRef;
+use cranelift_codegen::ir::{self, Block, InstBuilder, ValueLabel};
+use cranelift_codegen::timing;
+use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext, Variable};
+use wasmparser::{self, BinaryReader, FuncValidator, FunctionBody, WasmModuleResources};
+
+/// WebAssembly to Cranelift IR function translator.
+///
+/// A `FuncTranslator` is used to translate a binary WebAssembly function into Cranelift IR guided
+/// by a `FuncEnvironment` object. A single translator instance can be reused to translate multiple
+/// functions which will reduce heap allocation traffic.
+pub struct FuncTranslator {
+    func_ctx: FunctionBuilderContext,
+    state: FuncTranslationState,
+}
+
+impl FuncTranslator {
+    /// Create a new translator.
+    pub fn new() -> Self {
+        Self {
+            func_ctx: FunctionBuilderContext::new(),
+            state: FuncTranslationState::new(),
+        }
+    }
+
+    /// Translate a binary WebAssembly function.
+    ///
+    /// The `code` slice contains the binary WebAssembly *function code* as it appears in the code
+    /// section of a WebAssembly module, not including the initial size of the function code. The
+    /// slice is expected to contain two parts:
+    ///
+    /// - The declaration of *locals*, and
+    /// - The function *body* as an expression.
+    ///
+    /// See [the WebAssembly specification][wasm].
+    ///
+    /// [wasm]: https://webassembly.github.io/spec/core/binary/modules.html#code-section
+    ///
+    /// The Cranelift IR function `func` should be completely empty except for the `func.signature`
+    /// and `func.name` fields. The signature may contain special-purpose arguments which are not
+    /// regarded as WebAssembly local variables. Any signature arguments marked as
+    /// `ArgumentPurpose::Normal` are made accessible as WebAssembly local variables.
+    ///
+    pub fn translate<FE: FuncEnvironment + ?Sized>(
+        &mut self,
+        validator: &mut FuncValidator<impl WasmModuleResources>,
+        code: &[u8],
+        code_offset: usize,
+        func: &mut ir::Function,
+        environ: &mut FE,
+    ) -> WasmResult<()> {
+        self.translate_body(
+            validator,
+            FunctionBody::new(code_offset, code),
+            func,
+            environ,
+        )
+    }
+
+    /// Translate a binary WebAssembly function from a `FunctionBody`.
+    pub fn translate_body<FE: FuncEnvironment + ?Sized>(
+        &mut self,
+        validator: &mut FuncValidator<impl WasmModuleResources>,
+        body: FunctionBody<'_>,
+        func: &mut ir::Function,
+        environ: &mut FE,
+    ) -> WasmResult<()> {
+        let _tt = timing::wasm_translate_function();
+        let mut reader = body.get_binary_reader();
+        log::debug!(
+            "translate({} bytes, {}{})",
+            reader.bytes_remaining(),
+            func.name,
+            func.signature
+        );
+        debug_assert_eq!(func.dfg.num_blocks(), 0, "Function must be empty");
+        debug_assert_eq!(func.dfg.num_insts(), 0, "Function must be empty");
+
+        // This clears the `FunctionBuilderContext`.
+        let mut builder = FunctionBuilder::new(func, &mut self.func_ctx);
+        builder.set_srcloc(cur_srcloc(&reader));
+        let entry_block = builder.create_block();
+        builder.append_block_params_for_function_params(entry_block);
+        builder.switch_to_block(entry_block); // This also creates values for the arguments.
+        builder.seal_block(entry_block); // Declare all predecessors known.
+
+        // Make sure the entry block is inserted in the layout before we make any callbacks to
+        // `environ`. The callback functions may need to insert things in the entry block.
+        builder.ensure_inserted_block();
+
+        let num_params = declare_wasm_parameters(&mut builder, entry_block, environ);
+
+        // Set up the translation state with a single pushed control block representing the whole
+        // function and its return values.
+        let exit_block = builder.create_block();
+        builder.append_block_params_for_function_returns(exit_block);
+        self.state.initialize(&builder.func.signature, exit_block);
+
+        parse_local_decls(&mut reader, &mut builder, num_params, environ, validator)?;
+        parse_function_body(validator, reader, &mut builder, &mut self.state, environ)?;
+
+        builder.finalize();
+        Ok(())
+    }
+}
+
+/// Declare local variables for the signature parameters that correspond to WebAssembly locals.
+///
+/// Return the number of local variables declared.
+fn declare_wasm_parameters<FE: FuncEnvironment + ?Sized>(
+    builder: &mut FunctionBuilder,
+    entry_block: Block,
+    environ: &FE,
+) -> usize {
+    let sig_len = builder.func.signature.params.len();
+    let mut next_local = 0;
+    for i in 0..sig_len {
+        let param_type = builder.func.signature.params[i];
+        // There may be additional special-purpose parameters in addition to the normal WebAssembly
+        // signature parameters. For example, a `vmctx` pointer.
+        if environ.is_wasm_parameter(&builder.func.signature, i) {
+            // This is a normal WebAssembly signature parameter, so create a local for it.
+            let local = Variable::new(next_local);
+            builder.declare_var(local, param_type.value_type);
+            next_local += 1;
+
+            let param_value = builder.block_params(entry_block)[i];
+            builder.def_var(local, param_value);
+        }
+        if param_type.purpose == ir::ArgumentPurpose::VMContext {
+            let param_value = builder.block_params(entry_block)[i];
+            builder.set_val_label(param_value, get_vmctx_value_label());
+        }
+    }
+
+    next_local
+}
+
+/// Parse the local variable declarations that precede the function body.
+///
+/// Declare local variables, starting from `num_params`.
+fn parse_local_decls<FE: FuncEnvironment + ?Sized>(
+    reader: &mut BinaryReader,
+    builder: &mut FunctionBuilder,
+    num_params: usize,
+    environ: &mut FE,
+    validator: &mut FuncValidator<impl WasmModuleResources>,
+) -> WasmResult<()> {
+    let mut next_local = num_params;
+    let local_count = reader.read_var_u32()?;
+
+    for _ in 0..local_count {
+        builder.set_srcloc(cur_srcloc(reader));
+        let pos = reader.original_position();
+        let count = reader.read_var_u32()?;
+        let ty = reader.read_type()?;
+        validator.define_locals(pos, count, ty)?;
+        declare_locals(builder, count, ty, &mut next_local, environ)?;
+    }
+
+    Ok(())
+}
+
+/// Declare `count` local variables of the same type, starting from `next_local`.
+///
+/// Fail of too many locals are declared in the function, or if the type is not valid for a local.
+fn declare_locals<FE: FuncEnvironment + ?Sized>(
+    builder: &mut FunctionBuilder,
+    count: u32,
+    wasm_type: wasmparser::Type,
+    next_local: &mut usize,
+    environ: &mut FE,
+) -> WasmResult<()> {
+    // All locals are initialized to 0.
+    use wasmparser::Type::*;
+    let zeroval = match wasm_type {
+        I32 => builder.ins().iconst(ir::types::I32, 0),
+        I64 => builder.ins().iconst(ir::types::I64, 0),
+        F32 => builder.ins().f32const(ir::immediates::Ieee32::with_bits(0)),
+        F64 => builder.ins().f64const(ir::immediates::Ieee64::with_bits(0)),
+        V128 => {
+            let constant_handle = builder.func.dfg.constants.insert([0; 16].to_vec().into());
+            builder.ins().vconst(ir::types::I8X16, constant_handle)
+        }
+        ExternRef | FuncRef => {
+            environ.translate_ref_null(builder.cursor(), wasm_type.try_into()?)?
+        }
+        ty => return Err(wasm_unsupported!("unsupported local type {:?}", ty)),
+    };
+
+    let ty = builder.func.dfg.value_type(zeroval);
+    for _ in 0..count {
+        let local = Variable::new(*next_local);
+        builder.declare_var(local, ty);
+        builder.def_var(local, zeroval);
+        builder.set_val_label(zeroval, ValueLabel::new(*next_local));
+        *next_local += 1;
+    }
+    Ok(())
+}
+
+/// Parse the function body in `reader`.
+///
+/// This assumes that the local variable declarations have already been parsed and function
+/// arguments and locals are declared in the builder.
+fn parse_function_body<FE: FuncEnvironment + ?Sized>(
+    validator: &mut FuncValidator<impl WasmModuleResources>,
+    mut reader: BinaryReader,
+    builder: &mut FunctionBuilder,
+    state: &mut FuncTranslationState,
+    environ: &mut FE,
+) -> WasmResult<()> {
+    // The control stack is initialized with a single block representing the whole function.
+    debug_assert_eq!(state.control_stack.len(), 1, "State not initialized");
+
+    while !reader.eof() {
+        let pos = reader.original_position();
+        builder.set_srcloc(cur_srcloc(&reader));
+        let op = reader.read_operator()?;
+        validator.op(pos, &op)?;
+        environ.before_translate_operator(&op, builder, state)?;
+        translate_operator(validator, &op, builder, state, environ)?;
+        environ.after_translate_operator(&op, builder, state)?;
+    }
+    let pos = reader.original_position();
+    validator.finish(pos)?;
+
+    // The final `End` operator left us in the exit block where we need to manually add a return
+    // instruction.
+    //
+    // If the exit block is unreachable, it may not have the correct arguments, so we would
+    // generate a return instruction that doesn't match the signature.
+    if state.reachable {
+        debug_assert!(builder.is_pristine());
+        if !builder.is_unreachable() {
+            match environ.return_mode() {
+                ReturnMode::NormalReturns => {
+                    let return_types = wasm_param_types(&builder.func.signature.returns, |i| {
+                        environ.is_wasm_return(&builder.func.signature, i)
+                    });
+                    bitcast_arguments(&mut state.stack, &return_types, builder);
+                    builder.ins().return_(&state.stack)
+                }
+                ReturnMode::FallthroughReturn => builder.ins().fallthrough_return(&state.stack),
+            };
+        }
+    }
+
+    // Discard any remaining values on the stack. Either we just returned them,
+    // or the end of the function is unreachable.
+    state.stack.clear();
+
+    Ok(())
+}
+
+/// Get the current source location from a reader.
+fn cur_srcloc(reader: &BinaryReader) -> ir::SourceLoc {
+    // We record source locations as byte code offsets relative to the beginning of the file.
+    // This will wrap around if byte code is larger than 4 GB.
+    ir::SourceLoc::new(reader.original_position() as u32)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{FuncTranslator, ReturnMode};
+    use crate::environ::DummyEnvironment;
+    use cranelift_codegen::ir::types::I32;
+    use cranelift_codegen::{ir, isa, settings, Context};
+    use log::debug;
+    use target_lexicon::PointerWidth;
+    use wasmparser::{
+        FuncValidator, FunctionBody, Parser, ValidPayload, Validator, ValidatorResources,
+    };
+
+    #[test]
+    fn small1() {
+        // Implicit return.
+        let wasm = wat::parse_str(
+            "
+                (module
+                    (func $small2 (param i32) (result i32)
+                        (i32.add (get_local 0) (i32.const 1))
+                    )
+                )
+            ",
+        )
+        .unwrap();
+
+        let mut trans = FuncTranslator::new();
+        let flags = settings::Flags::new(settings::builder());
+        let runtime = DummyEnvironment::new(
+            isa::TargetFrontendConfig {
+                default_call_conv: isa::CallConv::Fast,
+                pointer_width: PointerWidth::U64,
+            },
+            ReturnMode::NormalReturns,
+            false,
+        );
+
+        let mut ctx = Context::new();
+
+        ctx.func.name = ir::ExternalName::testcase("small1");
+        ctx.func.signature.params.push(ir::AbiParam::new(I32));
+        ctx.func.signature.returns.push(ir::AbiParam::new(I32));
+
+        let (body, mut validator) = extract_func(&wasm);
+        trans
+            .translate_body(&mut validator, body, &mut ctx.func, &mut runtime.func_env())
+            .unwrap();
+        debug!("{}", ctx.func.display(None));
+        ctx.verify(&flags).unwrap();
+    }
+
+    #[test]
+    fn small2() {
+        // Same as above, but with an explicit return instruction.
+        let wasm = wat::parse_str(
+            "
+                (module
+                    (func $small2 (param i32) (result i32)
+                        (return (i32.add (get_local 0) (i32.const 1)))
+                    )
+                )
+            ",
+        )
+        .unwrap();
+
+        let mut trans = FuncTranslator::new();
+        let flags = settings::Flags::new(settings::builder());
+        let runtime = DummyEnvironment::new(
+            isa::TargetFrontendConfig {
+                default_call_conv: isa::CallConv::Fast,
+                pointer_width: PointerWidth::U64,
+            },
+            ReturnMode::NormalReturns,
+            false,
+        );
+
+        let mut ctx = Context::new();
+
+        ctx.func.name = ir::ExternalName::testcase("small2");
+        ctx.func.signature.params.push(ir::AbiParam::new(I32));
+        ctx.func.signature.returns.push(ir::AbiParam::new(I32));
+
+        let (body, mut validator) = extract_func(&wasm);
+        trans
+            .translate_body(&mut validator, body, &mut ctx.func, &mut runtime.func_env())
+            .unwrap();
+        debug!("{}", ctx.func.display(None));
+        ctx.verify(&flags).unwrap();
+    }
+
+    #[test]
+    fn infloop() {
+        // An infinite loop, no return instructions.
+        let wasm = wat::parse_str(
+            "
+                (module
+                    (func $infloop (result i32)
+                        (local i32)
+                        (loop (result i32)
+                            (i32.add (get_local 0) (i32.const 1))
+                            (set_local 0)
+                            (br 0)
+                        )
+                    )
+                )
+            ",
+        )
+        .unwrap();
+
+        let mut trans = FuncTranslator::new();
+        let flags = settings::Flags::new(settings::builder());
+        let runtime = DummyEnvironment::new(
+            isa::TargetFrontendConfig {
+                default_call_conv: isa::CallConv::Fast,
+                pointer_width: PointerWidth::U64,
+            },
+            ReturnMode::NormalReturns,
+            false,
+        );
+
+        let mut ctx = Context::new();
+
+        ctx.func.name = ir::ExternalName::testcase("infloop");
+        ctx.func.signature.returns.push(ir::AbiParam::new(I32));
+
+        let (body, mut validator) = extract_func(&wasm);
+        trans
+            .translate_body(&mut validator, body, &mut ctx.func, &mut runtime.func_env())
+            .unwrap();
+        debug!("{}", ctx.func.display(None));
+        ctx.verify(&flags).unwrap();
+    }
+
+    fn extract_func(wat: &[u8]) -> (FunctionBody<'_>, FuncValidator<ValidatorResources>) {
+        let mut validator = Validator::new();
+        for payload in Parser::new(0).parse_all(wat) {
+            match validator.payload(&payload.unwrap()).unwrap() {
+                ValidPayload::Func(validator, body) => return (body, validator),
+                _ => {}
+            }
+        }
+        panic!("failed to find function");
+    }
+}