3ed6fae7b3
* Add trampoline compilation support for lowered imports This commit adds support to the component model implementation for compiling trampolines suitable for calling host imports. Currently this is purely just the compilation side of things, modifying the wasmtime-cranelift crate and additionally filling out a new `VMComponentOffsets` type (similar to `VMOffsets`). The actual creation of a `VMComponentContext` is still not performed and will be a subsequent PR. Internally though some tests are actually possible with this where we at least assert that compilation of a component and creation of everything in-memory doesn't panic or trip any assertions, so some tests are added here for that as well. * Fix some test errors
59 lines
2.3 KiB
Rust
59 lines
2.3 KiB
Rust
use crate::component::{Component, ComponentTypes, LowerImport, LoweredIndex};
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use crate::PrimaryMap;
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use anyhow::Result;
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use object::write::Object;
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use serde::{Deserialize, Serialize};
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use std::any::Any;
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/// Description of where a trampoline is located in the text section of a
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/// compiled image.
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#[derive(Serialize, Deserialize)]
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pub struct TrampolineInfo {
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/// The byte offset from the start of the text section where this trampoline
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/// starts.
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pub start: u32,
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/// The byte length of this trampoline's function body.
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pub length: u32,
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}
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/// Compilation support necessary for components.
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pub trait ComponentCompiler: Send + Sync {
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/// Creates a trampoline for a `canon.lower`'d host function.
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///
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/// This function will create a suitable trampoline which can be called from
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/// WebAssembly code and which will then call into host code. The signature
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/// of this generated trampoline should have the appropriate wasm ABI for
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/// the `lowering.canonical_abi` type signature (e.g. System-V).
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///
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/// The generated trampoline will interpret its first argument as a
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/// `*mut VMComponentContext` and use the `VMComponentOffsets` for
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/// `component` to read necessary data (as specified by `lowering.options`)
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/// and call the host function pointer. Notably the host function pointer
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/// has the signature `VMLoweringCallee` where many of the arguments are
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/// loaded from known offsets (for this particular generated trampoline)
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/// from the `VMComponentContext`.
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///
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/// Returns a compiler-specific `Box<dyn Any>` which can be passed later to
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/// `emit_obj` to crate an elf object.
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fn compile_lowered_trampoline(
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&self,
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component: &Component,
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lowering: &LowerImport,
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types: &ComponentTypes,
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) -> Result<Box<dyn Any + Send>>;
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/// Emits the `trampolines` specified into the in-progress ELF object
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/// specified by `obj`.
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///
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/// Returns a map of trampoline information for where to find them all in
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/// the text section.
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///
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/// Note that this will also prepare unwinding information for all the
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/// trampolines as necessary.
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fn emit_obj(
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&self,
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trampolines: PrimaryMap<LoweredIndex, Box<dyn Any + Send>>,
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obj: &mut Object<'static>,
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) -> Result<PrimaryMap<LoweredIndex, TrampolineInfo>>;
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}
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