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* aarch64: Initial work to transition backend to ISLE This commit is what is hoped to be the initial commit towards migrating the aarch64 backend to ISLE. There's seemingly a lot of changes here but it's intended to largely be code motion. The current thinking is to closely follow the x64 backend for how all this is handled and organized. Major changes in this PR are: * The `Inst` enum is now defined in ISLE. This avoids having to define it in two places (once in Rust and once in ISLE). I've preserved all the comments in the ISLE and otherwise this isn't actually a functional change from the Rust perspective, it's still the same enum according to Rust. * Lots of little enums and things were moved to ISLE as well. As with `Inst` their definitions didn't change, only where they're defined. This will give future ISLE PRs access to all these operations. * Initial code for lowering `iconst`, `null`, and `bconst` are implemented. Ironically none of this is actually used right now because constant lowering is handled in `put_input_in_regs` which specially handles constants. Nonetheless I wanted to get at least something simple working which shows off how to special case various things that are specific to AArch64. In a future PR I plan to hook up const-lowering in ISLE to this path so even though `iconst`-the-clif-instruction is never lowered this should use the const lowering defined in ISLE rather than elsewhere in the backend (eventually leading to the deletion of the non-ISLE lowering). * The `IsleContext` skeleton is created and set up for future additions. * Some code for ISLE that's shared across all backends now lives in `isle_prelude_methods!()` and is deduplicated between the AArch64 backend and the x64 backend. * Register mapping is tweaked to do the same thing for AArch64 that it does for x64. Namely mapping virtual registers is supported instead of just virtual to machine registers. My main goal with this PR was to get AArch64 into a place where new instructions can be added with relative ease. Additionally I'm hoping to figure out as part of this change how much to share for ISLE between AArch64 and x64 (and other backends). * Don't use priorities with rules * Update .gitattributes with concise syntax * Deduplicate some type definitions * Rebuild ISLE * Move isa::isle to machinst::isle
Cranelift Code Generator
A Bytecode Alliance project
Cranelift is a low-level retargetable code generator. It translates a target-independent intermediate representation into executable machine code.
For more information, see the documentation.
For an example of how to use the JIT, see the JIT Demo, which implements a toy language.
For an example of how to use Cranelift to run WebAssembly code, see Wasmtime, which implements a standalone, embeddable, VM using Cranelift.
Status
Cranelift currently supports enough functionality to run a wide variety of programs, including all the functionality needed to execute WebAssembly MVP functions, although it needs to be used within an external WebAssembly embedding to be part of a complete WebAssembly implementation.
The x86-64 backend is currently the most complete and stable; other architectures are in various stages of development. Cranelift currently supports both the System V AMD64 ABI calling convention used on many platforms and the Windows x64 calling convention. The performance of code produced by Cranelift is not yet impressive, though we have plans to fix that.
The core codegen crates have minimal dependencies, support no_std mode (see below), and do not require any host floating-point support, and do not use callstack recursion.
Cranelift does not yet perform mitigations for Spectre or related security issues, though it may do so in the future. It does not currently make any security-relevant instruction timing guarantees. It has seen a fair amount of testing and fuzzing, although more work is needed before it would be ready for a production use case.
Cranelift's APIs are not yet stable.
Cranelift currently requires Rust 1.37 or later to build.
Contributing
If you're interested in contributing to Cranelift: thank you! We have a contributing guide which will help you getting involved in the Cranelift project.
Planned uses
Cranelift is designed to be a code generator for WebAssembly, but it is general enough to be useful elsewhere too. The initial planned uses that affected its design are:
- WebAssembly compiler for the SpiderMonkey engine in Firefox.
- Backend for the IonMonkey JavaScript JIT compiler in Firefox.
- Debug build backend for the Rust compiler.
- Wasmtime non-Web wasm engine.
Building Cranelift
Cranelift uses a conventional Cargo build process.
Cranelift consists of a collection of crates, and uses a Cargo
Workspace,
so for some cargo commands, such as cargo test, the --all is needed
to tell cargo to visit all of the crates.
test-all.sh at the top level is a script which runs all the cargo
tests and also performs code format, lint, and documentation checks.
Building with no_std
The following crates support `no_std`, although they do depend on liballoc:
- cranelift-entity
- cranelift-bforest
- cranelift-codegen
- cranelift-frontend
- cranelift-native
- cranelift-wasm
- cranelift-module
- cranelift-preopt
- cranelift
To use no_std mode, disable the std feature and enable the core feature. This currently requires nightly rust.
For example, to build `cranelift-codegen`:
cd cranelift-codegen
cargo build --no-default-features --features core
Or, when using cranelift-codegen as a dependency (in Cargo.toml):
[dependency.cranelift-codegen]
...
default-features = false
features = ["core"]
no_std support is currently "best effort". We won't try to break it, and we'll accept patches fixing problems, however we don't expect all developers to build and test no_std when submitting patches. Accordingly, the ./test-all.sh script does not test no_std.
There is a separate ./test-no_std.sh script that tests the no_std support in packages which support it.
It's important to note that cranelift still needs liballoc to compile. Thus, whatever environment is used must implement an allocator.
Also, to allow the use of HashMaps with no_std, an external crate called hashmap_core is pulled in (via the core feature). This is mostly the same as std::collections::HashMap, except that it doesn't have DOS protection. Just something to think about.
Log configuration
Cranelift uses the log crate to log messages at various levels. It doesn't
specify any maximal logging level, so embedders can choose what it should be;
however, this can have an impact of Cranelift's code size. You can use log
features to reduce the maximum logging level. For instance if you want to limit
the level of logging to warn messages and above in release mode:
[dependency.log]
...
features = ["release_max_level_warn"]
Editor Support
Editor support for working with Cranelift IR (clif) files: