8a9b1a9025
This is the implementation of https://github.com/bytecodealliance/wasmtime/issues/4155, using the "inverted API" approach suggested by @cfallin (thanks!) in Cranelift, and trait object to provide a backend for an all-included experience in Wasmtime. After the suggestion of Chris, `Function` has been split into mostly two parts: - on the one hand, `FunctionStencil` contains all the fields required during compilation, and that act as a compilation cache key: if two function stencils are the same, then the result of their compilation (`CompiledCodeBase<Stencil>`) will be the same. This makes caching trivial, as the only thing to cache is the `FunctionStencil`. - on the other hand, `FunctionParameters` contain the... function parameters that are required to finalize the result of compilation into a `CompiledCode` (aka `CompiledCodeBase<Final>`) with proper final relocations etc., by applying fixups and so on. Most changes are here to accomodate those requirements, in particular that `FunctionStencil` should be `Hash`able to be used as a key in the cache: - most source locations are now relative to a base source location in the function, and as such they're encoded as `RelSourceLoc` in the `FunctionStencil`. This required changes so that there's no need to explicitly mark a `SourceLoc` as the base source location, it's automatically detected instead the first time a non-default `SourceLoc` is set. - user-defined external names in the `FunctionStencil` (aka before this patch `ExternalName::User { namespace, index }`) are now references into an external table of `UserExternalNameRef -> UserExternalName`, present in the `FunctionParameters`, and must be explicitly declared using `Function::declare_imported_user_function`. - some refactorings have been made for function names: - `ExternalName` was used as the type for a `Function`'s name; while it thus allowed `ExternalName::Libcall` in this place, this would have been quite confusing to use it there. Instead, a new enum `UserFuncName` is introduced for this name, that's either a user-defined function name (the above `UserExternalName`) or a test case name. - The future of `ExternalName` is likely to become a full reference into the `FunctionParameters`'s mapping, instead of being "either a handle for user-defined external names, or the thing itself for other variants". I'm running out of time to do this, and this is not trivial as it implies touching ISLE which I'm less familiar with. The cache computes a sha256 hash of the `FunctionStencil`, and uses this as the cache key. No equality check (using `PartialEq`) is performed in addition to the hash being the same, as we hope that this is sufficient data to avoid collisions. A basic fuzz target has been introduced that tries to do the bare minimum: - check that a function successfully compiled and cached will be also successfully reloaded from the cache, and returns the exact same function. - check that a trivial modification in the external mapping of `UserExternalNameRef -> UserExternalName` hits the cache, and that other modifications don't hit the cache. - This last check is less efficient and less likely to happen, so probably should be rethought a bit. Thanks to both @alexcrichton and @cfallin for your very useful feedback on Zulip. Some numbers show that for a large wasm module we're using internally, this is a 20% compile-time speedup, because so many `FunctionStencil`s are the same, even within a single module. For a group of modules that have a lot of code in common, we get hit rates up to 70% when they're used together. When a single function changes in a wasm module, every other function is reloaded; that's still slower than I expect (between 10% and 50% of the overall compile time), so there's likely room for improvement. Fixes #4155.
667 lines
23 KiB
Rust
667 lines
23 KiB
Rust
//! Cursor library.
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//!
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//! This module defines cursor data types that can be used for inserting instructions.
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use crate::ir;
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/// The possible positions of a cursor.
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#[derive(Clone, Copy, PartialEq, Eq, Debug)]
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pub enum CursorPosition {
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/// Cursor is not pointing anywhere. No instructions can be inserted.
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Nowhere,
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/// Cursor is pointing at an existing instruction.
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/// New instructions will be inserted *before* the current instruction.
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At(ir::Inst),
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/// Cursor is before the beginning of a block. No instructions can be inserted. Calling
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/// `next_inst()` will move to the first instruction in the block.
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Before(ir::Block),
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/// Cursor is pointing after the end of a block.
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/// New instructions will be appended to the block.
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After(ir::Block),
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}
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/// All cursor types implement the `Cursor` which provides common navigation operations.
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pub trait Cursor {
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/// Get the current cursor position.
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fn position(&self) -> CursorPosition;
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/// Set the current position.
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fn set_position(&mut self, pos: CursorPosition);
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/// Get the source location that should be assigned to new instructions.
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fn srcloc(&self) -> ir::SourceLoc;
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/// Set the source location that should be assigned to new instructions.
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fn set_srcloc(&mut self, srcloc: ir::SourceLoc);
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/// Borrow a reference to the function layout that this cursor is navigating.
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fn layout(&self) -> &ir::Layout;
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/// Borrow a mutable reference to the function layout that this cursor is navigating.
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fn layout_mut(&mut self) -> &mut ir::Layout;
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/// Exchange this cursor for one with a set source location.
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///
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/// This is intended to be used as a builder method:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block, SourceLoc};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_func(func: &mut Function, srcloc: SourceLoc) {
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/// let mut pos = FuncCursor::new(func).with_srcloc(srcloc);
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///
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/// // Use `pos`...
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/// }
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/// ```
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fn with_srcloc(mut self, srcloc: ir::SourceLoc) -> Self
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where
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Self: Sized,
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{
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self.set_srcloc(srcloc);
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self
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}
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/// Rebuild this cursor positioned at `pos`.
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fn at_position(mut self, pos: CursorPosition) -> Self
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where
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Self: Sized,
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{
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self.set_position(pos);
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self
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}
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/// Rebuild this cursor positioned at `inst`.
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///
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/// This is intended to be used as a builder method:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block, Inst};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_func(func: &mut Function, inst: Inst) {
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/// let mut pos = FuncCursor::new(func).at_inst(inst);
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///
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/// // Use `pos`...
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/// }
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/// ```
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fn at_inst(mut self, inst: ir::Inst) -> Self
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where
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Self: Sized,
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{
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self.goto_inst(inst);
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self
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}
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/// Rebuild this cursor positioned at the first insertion point for `block`.
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/// This differs from `at_first_inst` in that it doesn't assume that any
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/// instructions have been inserted into `block` yet.
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///
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/// This is intended to be used as a builder method:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block, Inst};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_func(func: &mut Function, block: Block) {
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/// let mut pos = FuncCursor::new(func).at_first_insertion_point(block);
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///
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/// // Use `pos`...
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/// }
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/// ```
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fn at_first_insertion_point(mut self, block: ir::Block) -> Self
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where
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Self: Sized,
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{
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self.goto_first_insertion_point(block);
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self
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}
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/// Rebuild this cursor positioned at the first instruction in `block`.
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///
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/// This is intended to be used as a builder method:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block, Inst};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_func(func: &mut Function, block: Block) {
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/// let mut pos = FuncCursor::new(func).at_first_inst(block);
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///
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/// // Use `pos`...
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/// }
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/// ```
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fn at_first_inst(mut self, block: ir::Block) -> Self
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where
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Self: Sized,
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{
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self.goto_first_inst(block);
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self
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}
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/// Rebuild this cursor positioned at the last instruction in `block`.
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///
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/// This is intended to be used as a builder method:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block, Inst};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_func(func: &mut Function, block: Block) {
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/// let mut pos = FuncCursor::new(func).at_last_inst(block);
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///
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/// // Use `pos`...
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/// }
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/// ```
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fn at_last_inst(mut self, block: ir::Block) -> Self
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where
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Self: Sized,
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{
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self.goto_last_inst(block);
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self
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}
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/// Rebuild this cursor positioned after `inst`.
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///
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/// This is intended to be used as a builder method:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block, Inst};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_func(func: &mut Function, inst: Inst) {
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/// let mut pos = FuncCursor::new(func).after_inst(inst);
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///
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/// // Use `pos`...
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/// }
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/// ```
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fn after_inst(mut self, inst: ir::Inst) -> Self
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where
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Self: Sized,
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{
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self.goto_after_inst(inst);
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self
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}
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/// Rebuild this cursor positioned at the top of `block`.
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///
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/// This is intended to be used as a builder method:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block, Inst};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_func(func: &mut Function, block: Block) {
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/// let mut pos = FuncCursor::new(func).at_top(block);
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///
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/// // Use `pos`...
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/// }
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/// ```
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fn at_top(mut self, block: ir::Block) -> Self
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where
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Self: Sized,
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{
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self.goto_top(block);
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self
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}
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/// Rebuild this cursor positioned at the bottom of `block`.
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///
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/// This is intended to be used as a builder method:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block, Inst};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_func(func: &mut Function, block: Block) {
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/// let mut pos = FuncCursor::new(func).at_bottom(block);
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///
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/// // Use `pos`...
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/// }
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/// ```
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fn at_bottom(mut self, block: ir::Block) -> Self
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where
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Self: Sized,
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{
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self.goto_bottom(block);
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self
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}
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/// Get the block corresponding to the current position.
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fn current_block(&self) -> Option<ir::Block> {
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use self::CursorPosition::*;
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match self.position() {
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Nowhere => None,
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At(inst) => self.layout().inst_block(inst),
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Before(block) | After(block) => Some(block),
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}
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}
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/// Get the instruction corresponding to the current position, if any.
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fn current_inst(&self) -> Option<ir::Inst> {
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use self::CursorPosition::*;
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match self.position() {
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At(inst) => Some(inst),
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_ => None,
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}
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}
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/// Go to the position after a specific instruction, which must be inserted
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/// in the layout. New instructions will be inserted after `inst`.
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fn goto_after_inst(&mut self, inst: ir::Inst) {
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debug_assert!(self.layout().inst_block(inst).is_some());
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let new_pos = if let Some(next) = self.layout().next_inst(inst) {
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CursorPosition::At(next)
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} else {
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CursorPosition::After(
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self.layout()
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.inst_block(inst)
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.expect("current instruction removed?"),
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)
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};
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self.set_position(new_pos);
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}
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/// Go to a specific instruction which must be inserted in the layout.
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/// New instructions will be inserted before `inst`.
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fn goto_inst(&mut self, inst: ir::Inst) {
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debug_assert!(self.layout().inst_block(inst).is_some());
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self.set_position(CursorPosition::At(inst));
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}
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/// Go to the position for inserting instructions at the beginning of `block`,
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/// which unlike `goto_first_inst` doesn't assume that any instructions have
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/// been inserted into `block` yet.
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fn goto_first_insertion_point(&mut self, block: ir::Block) {
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if let Some(inst) = self.layout().first_inst(block) {
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self.goto_inst(inst);
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} else {
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self.goto_bottom(block);
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}
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}
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/// Go to the first instruction in `block`.
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fn goto_first_inst(&mut self, block: ir::Block) {
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let inst = self.layout().first_inst(block).expect("Empty block");
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self.goto_inst(inst);
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}
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/// Go to the last instruction in `block`.
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fn goto_last_inst(&mut self, block: ir::Block) {
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let inst = self.layout().last_inst(block).expect("Empty block");
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self.goto_inst(inst);
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}
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/// Go to the top of `block` which must be inserted into the layout.
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/// At this position, instructions cannot be inserted, but `next_inst()` will move to the first
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/// instruction in `block`.
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fn goto_top(&mut self, block: ir::Block) {
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debug_assert!(self.layout().is_block_inserted(block));
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self.set_position(CursorPosition::Before(block));
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}
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/// Go to the bottom of `block` which must be inserted into the layout.
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/// At this position, inserted instructions will be appended to `block`.
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fn goto_bottom(&mut self, block: ir::Block) {
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debug_assert!(self.layout().is_block_inserted(block));
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self.set_position(CursorPosition::After(block));
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}
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/// Go to the top of the next block in layout order and return it.
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///
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/// - If the cursor wasn't pointing at anything, go to the top of the first block in the
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/// function.
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/// - If there are no more blocks, leave the cursor pointing at nothing and return `None`.
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///
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/// # Examples
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///
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/// The `next_block()` method is intended for iterating over the blocks in layout order:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_func(func: &mut Function) {
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/// let mut cursor = FuncCursor::new(func);
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/// while let Some(block) = cursor.next_block() {
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/// // Edit block.
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/// }
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/// }
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/// ```
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fn next_block(&mut self) -> Option<ir::Block> {
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let next = if let Some(block) = self.current_block() {
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self.layout().next_block(block)
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} else {
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self.layout().entry_block()
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};
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self.set_position(match next {
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Some(block) => CursorPosition::Before(block),
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None => CursorPosition::Nowhere,
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});
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next
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}
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/// Go to the bottom of the previous block in layout order and return it.
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///
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/// - If the cursor wasn't pointing at anything, go to the bottom of the last block in the
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/// function.
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/// - If there are no more blocks, leave the cursor pointing at nothing and return `None`.
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///
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/// # Examples
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///
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/// The `prev_block()` method is intended for iterating over the blocks in backwards layout order:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_func(func: &mut Function) {
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/// let mut cursor = FuncCursor::new(func);
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/// while let Some(block) = cursor.prev_block() {
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/// // Edit block.
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/// }
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/// }
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/// ```
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fn prev_block(&mut self) -> Option<ir::Block> {
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let prev = if let Some(block) = self.current_block() {
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self.layout().prev_block(block)
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} else {
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self.layout().last_block()
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};
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self.set_position(match prev {
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Some(block) => CursorPosition::After(block),
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None => CursorPosition::Nowhere,
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});
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prev
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}
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/// Move to the next instruction in the same block and return it.
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///
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/// - If the cursor was positioned before a block, go to the first instruction in that block.
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/// - If there are no more instructions in the block, go to the `After(block)` position and return
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/// `None`.
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/// - If the cursor wasn't pointing anywhere, keep doing that.
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///
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/// This method will never move the cursor to a different block.
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///
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/// # Examples
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///
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/// The `next_inst()` method is intended for iterating over the instructions in a block like
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/// this:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_block(func: &mut Function, block: Block) {
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/// let mut cursor = FuncCursor::new(func).at_top(block);
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/// while let Some(inst) = cursor.next_inst() {
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/// // Edit instructions...
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/// }
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/// }
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/// ```
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/// The loop body can insert and remove instructions via the cursor.
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///
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/// Iterating over all the instructions in a function looks like this:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_func(func: &mut Function) {
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/// let mut cursor = FuncCursor::new(func);
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/// while let Some(block) = cursor.next_block() {
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/// while let Some(inst) = cursor.next_inst() {
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/// // Edit instructions...
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/// }
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/// }
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/// }
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/// ```
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fn next_inst(&mut self) -> Option<ir::Inst> {
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use self::CursorPosition::*;
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match self.position() {
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Nowhere | After(..) => None,
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At(inst) => {
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if let Some(next) = self.layout().next_inst(inst) {
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self.set_position(At(next));
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Some(next)
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} else {
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let pos = After(
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self.layout()
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.inst_block(inst)
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.expect("current instruction removed?"),
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);
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self.set_position(pos);
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None
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}
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}
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Before(block) => {
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if let Some(next) = self.layout().first_inst(block) {
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self.set_position(At(next));
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Some(next)
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} else {
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self.set_position(After(block));
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None
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}
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}
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}
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}
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/// Move to the previous instruction in the same block and return it.
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///
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/// - If the cursor was positioned after a block, go to the last instruction in that block.
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/// - If there are no more instructions in the block, go to the `Before(block)` position and return
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/// `None`.
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/// - If the cursor wasn't pointing anywhere, keep doing that.
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///
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/// This method will never move the cursor to a different block.
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///
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/// # Examples
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///
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/// The `prev_inst()` method is intended for iterating backwards over the instructions in an
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/// block like this:
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///
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/// ```
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/// # use cranelift_codegen::ir::{Function, Block};
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/// # use cranelift_codegen::cursor::{Cursor, FuncCursor};
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/// fn edit_block(func: &mut Function, block: Block) {
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/// let mut cursor = FuncCursor::new(func).at_bottom(block);
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/// while let Some(inst) = cursor.prev_inst() {
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/// // Edit instructions...
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/// }
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/// }
|
|
/// ```
|
|
fn prev_inst(&mut self) -> Option<ir::Inst> {
|
|
use self::CursorPosition::*;
|
|
match self.position() {
|
|
Nowhere | Before(..) => None,
|
|
At(inst) => {
|
|
if let Some(prev) = self.layout().prev_inst(inst) {
|
|
self.set_position(At(prev));
|
|
Some(prev)
|
|
} else {
|
|
let pos = Before(
|
|
self.layout()
|
|
.inst_block(inst)
|
|
.expect("current instruction removed?"),
|
|
);
|
|
self.set_position(pos);
|
|
None
|
|
}
|
|
}
|
|
After(block) => {
|
|
if let Some(prev) = self.layout().last_inst(block) {
|
|
self.set_position(At(prev));
|
|
Some(prev)
|
|
} else {
|
|
self.set_position(Before(block));
|
|
None
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Insert an instruction at the current position.
|
|
///
|
|
/// - If pointing at an instruction, the new instruction is inserted before the current
|
|
/// instruction.
|
|
/// - If pointing at the bottom of a block, the new instruction is appended to the block.
|
|
/// - Otherwise panic.
|
|
///
|
|
/// In either case, the cursor is not moved, such that repeated calls to `insert_inst()` causes
|
|
/// instructions to appear in insertion order in the block.
|
|
fn insert_inst(&mut self, inst: ir::Inst) {
|
|
use self::CursorPosition::*;
|
|
match self.position() {
|
|
Nowhere | Before(..) => panic!("Invalid insert_inst position"),
|
|
At(cur) => self.layout_mut().insert_inst(inst, cur),
|
|
After(block) => self.layout_mut().append_inst(inst, block),
|
|
}
|
|
}
|
|
|
|
/// Remove the instruction under the cursor.
|
|
///
|
|
/// The cursor is left pointing at the position following the current instruction.
|
|
///
|
|
/// Return the instruction that was removed.
|
|
fn remove_inst(&mut self) -> ir::Inst {
|
|
let inst = self.current_inst().expect("No instruction to remove");
|
|
self.next_inst();
|
|
self.layout_mut().remove_inst(inst);
|
|
inst
|
|
}
|
|
|
|
/// Remove the instruction under the cursor.
|
|
///
|
|
/// The cursor is left pointing at the position preceding the current instruction.
|
|
///
|
|
/// Return the instruction that was removed.
|
|
fn remove_inst_and_step_back(&mut self) -> ir::Inst {
|
|
let inst = self.current_inst().expect("No instruction to remove");
|
|
self.prev_inst();
|
|
self.layout_mut().remove_inst(inst);
|
|
inst
|
|
}
|
|
|
|
/// Insert a block at the current position and switch to it.
|
|
///
|
|
/// As far as possible, this method behaves as if the block header were an instruction inserted
|
|
/// at the current position.
|
|
///
|
|
/// - If the cursor is pointing at an existing instruction, *the current block is split in two*
|
|
/// and the current instruction becomes the first instruction in the inserted block.
|
|
/// - If the cursor points at the bottom of a block, the new block is inserted after the current
|
|
/// one, and moved to the bottom of the new block where instructions can be appended.
|
|
/// - If the cursor points to the top of a block, the new block is inserted above the current one.
|
|
/// - If the cursor is not pointing at anything, the new block is placed last in the layout.
|
|
///
|
|
/// This means that it is always valid to call this method, and it always leaves the cursor in
|
|
/// a state that will insert instructions into the new block.
|
|
fn insert_block(&mut self, new_block: ir::Block) {
|
|
use self::CursorPosition::*;
|
|
match self.position() {
|
|
At(inst) => {
|
|
self.layout_mut().split_block(new_block, inst);
|
|
// All other cases move to `After(block)`, but in this case we'll stay `At(inst)`.
|
|
return;
|
|
}
|
|
Nowhere => self.layout_mut().append_block(new_block),
|
|
Before(block) => self.layout_mut().insert_block(new_block, block),
|
|
After(block) => self.layout_mut().insert_block_after(new_block, block),
|
|
}
|
|
// For everything but `At(inst)` we end up appending to the new block.
|
|
self.set_position(After(new_block));
|
|
}
|
|
}
|
|
|
|
/// Function cursor.
|
|
///
|
|
/// A `FuncCursor` holds a mutable reference to a whole `ir::Function` while keeping a position
|
|
/// too. The function can be re-borrowed by accessing the public `cur.func` member.
|
|
///
|
|
/// This cursor is for use before legalization. The inserted instructions are not given an
|
|
/// encoding.
|
|
pub struct FuncCursor<'f> {
|
|
pos: CursorPosition,
|
|
srcloc: ir::SourceLoc,
|
|
|
|
/// The referenced function.
|
|
pub func: &'f mut ir::Function,
|
|
}
|
|
|
|
impl<'f> FuncCursor<'f> {
|
|
/// Create a new `FuncCursor` pointing nowhere.
|
|
pub fn new(func: &'f mut ir::Function) -> Self {
|
|
Self {
|
|
pos: CursorPosition::Nowhere,
|
|
srcloc: Default::default(),
|
|
func,
|
|
}
|
|
}
|
|
|
|
/// Use the source location of `inst` for future instructions.
|
|
pub fn use_srcloc(&mut self, inst: ir::Inst) {
|
|
self.srcloc = self.func.srcloc(inst);
|
|
}
|
|
|
|
/// Create an instruction builder that inserts an instruction at the current position.
|
|
pub fn ins(&mut self) -> ir::InsertBuilder<&mut FuncCursor<'f>> {
|
|
ir::InsertBuilder::new(self)
|
|
}
|
|
}
|
|
|
|
impl<'f> Cursor for FuncCursor<'f> {
|
|
fn position(&self) -> CursorPosition {
|
|
self.pos
|
|
}
|
|
|
|
fn set_position(&mut self, pos: CursorPosition) {
|
|
self.pos = pos
|
|
}
|
|
|
|
fn srcloc(&self) -> ir::SourceLoc {
|
|
self.srcloc
|
|
}
|
|
|
|
fn set_srcloc(&mut self, srcloc: ir::SourceLoc) {
|
|
self.func.params.ensure_base_srcloc(srcloc);
|
|
self.srcloc = srcloc;
|
|
}
|
|
|
|
fn layout(&self) -> &ir::Layout {
|
|
&self.func.layout
|
|
}
|
|
|
|
fn layout_mut(&mut self) -> &mut ir::Layout {
|
|
&mut self.func.layout
|
|
}
|
|
}
|
|
|
|
impl<'c, 'f> ir::InstInserterBase<'c> for &'c mut FuncCursor<'f> {
|
|
fn data_flow_graph(&self) -> &ir::DataFlowGraph {
|
|
&self.func.dfg
|
|
}
|
|
|
|
fn data_flow_graph_mut(&mut self) -> &mut ir::DataFlowGraph {
|
|
&mut self.func.dfg
|
|
}
|
|
|
|
fn insert_built_inst(self, inst: ir::Inst) -> &'c mut ir::DataFlowGraph {
|
|
// TODO: Remove this assertion once #796 is fixed.
|
|
#[cfg(debug_assertions)]
|
|
{
|
|
if let CursorPosition::At(_) = self.position() {
|
|
if let Some(curr) = self.current_inst() {
|
|
if let Some(prev) = self.layout().prev_inst(curr) {
|
|
let prev_op = self.data_flow_graph()[prev].opcode();
|
|
let inst_op = self.data_flow_graph()[inst].opcode();
|
|
let curr_op = self.data_flow_graph()[curr].opcode();
|
|
if prev_op.is_branch()
|
|
&& !prev_op.is_terminator()
|
|
&& !inst_op.is_terminator()
|
|
{
|
|
panic!(
|
|
"Inserting instruction {} after {}, and before {}",
|
|
inst_op, prev_op, curr_op
|
|
)
|
|
}
|
|
};
|
|
};
|
|
};
|
|
}
|
|
self.insert_inst(inst);
|
|
if !self.srcloc.is_default() {
|
|
self.func.set_srcloc(inst, self.srcloc);
|
|
}
|
|
&mut self.func.dfg
|
|
}
|
|
}
|