776ab988c1
Support tail calls in mir via `TerminatorKind::TailCall`
This is one of the interesting bits in tail call implementation — MIR support.
This adds a new `TerminatorKind` which represents a tail call:
```rust
TailCall {
func: Operand<'tcx>,
args: Vec<Operand<'tcx>>,
fn_span: Span,
},
```
*Structurally* this is very similar to a normal `Call` but is missing a few fields:
- `destination` — tail calls don't write to destination, instead they pass caller's destination to the callee (such that eventual `return` will write to the caller of the function that used tail call)
- `target` — similarly to `destination` tail calls pass the caller's return address to the callee, so there is nothing to do
- `unwind` — I _think_ this is applicable too, although it's a bit confusing
- `call_source` — `become` forbids operators and is not created as a lowering of something else; tail calls always come from HIR (at least for now)
It might be helpful to read the interpreter implementation to understand what `TailCall` means exactly, although I've tried documenting it too.
-----
There are a few `FIXME`-questions still left, ideally we'd be able to answer them during review ':)
-----
r? `@oli-obk`
cc `@scottmcm` `@DrMeepster` `@JakobDegen`
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| config.txt | ||
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| LICENSE-MIT | ||
| Readme.md | ||
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| test.sh | ||
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| y.sh | ||
Cranelift codegen backend for rust
The goal of this project is to create an alternative codegen backend for the rust compiler based on Cranelift. This has the potential to improve compilation times in debug mode. If your project doesn't use any of the things listed under "Not yet supported", it should work fine. If not please open an issue.
Download using Rustup
The Cranelift codegen backend is distributed in nightly builds on Linux and x86_64 macOS. If you want to install it using Rustup, you can do that by running:
$ rustup component add rustc-codegen-cranelift-preview --toolchain nightly
Once it is installed, you can enable it with one of the following approaches:
CARGO_PROFILE_DEV_CODEGEN_BACKEND=cranelift cargo +nightly build -Zcodegen-backendRUSTFLAGS="-Zcodegen-backend=cranelift" cargo +nightly build- Add the following to
.cargo/config.toml:[unstable] codegen-backend = true [profile.dev] codegen-backend = "cranelift" - Add the following to
Cargo.toml:# This line needs to come before anything else in Cargo.toml cargo-features = ["codegen-backend"] [profile.dev] codegen-backend = "cranelift"
Precompiled builds
You can also download a pre-built version from the releases page.
Extract the dist directory in the archive anywhere you want.
If you want to use cargo clif build instead of having to specify the full path to the cargo-clif executable, you can add the bin subdirectory of the extracted dist directory to your PATH.
(tutorial for Windows, and for Linux/MacOS).
Building and testing
If you want to build the backend manually, you can download it from GitHub and build it yourself:
$ git clone https://github.com/rust-lang/rustc_codegen_cranelift
$ cd rustc_codegen_cranelift
$ ./y.sh prepare
$ ./y.sh build
To run the test suite replace the last command with:
$ ./test.sh
For more docs on how to build and test see build_system/usage.txt or the help message of ./y.sh.
Platform support
| OS \ architecture | x86_64 | AArch64 | Riscv64 | s390x (System-Z) |
|---|---|---|---|---|
| Linux | ✅ | ✅ | ✅1 | ✅1 |
| FreeBSD | ✅1 | ❓ | ❓ | ❓ |
| AIX | ❌2 | N/A | N/A | ❌2 |
| Other unixes | ❓ | ❓ | ❓ | ❓ |
| macOS | ✅ | ✅1 | N/A | N/A |
| Windows | ✅1 | ❌ | N/A | N/A |
✅: Fully supported and tested ❓: Maybe supported, not tested ❌: Not supported at all
Not all targets are available as rustup component for nightly. See notes in the platform support matrix.
Usage
rustc_codegen_cranelift can be used as a near-drop-in replacement for cargo build or cargo run for existing projects.
Assuming $cg_clif_dir is the directory you cloned this repo into and you followed the instructions (y.sh prepare and y.sh build or test.sh).
In the directory with your project (where you can do the usual cargo build), run:
$ $cg_clif_dir/dist/cargo-clif build
This will build your project with rustc_codegen_cranelift instead of the usual LLVM backend.
For additional ways to use rustc_codegen_cranelift like the JIT mode see usage.md.
Building and testing with changes in rustc code
See rustc_testing.md.
Not yet supported
- SIMD (tracked here,
std::simdfully works,std::archis partially supported) - Unwinding on panics (no cranelift support,
-Cpanic=abortis enabled by default)
License
Licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you shall be dual licensed as above, without any additional terms or conditions.