mirror
/
rustc-dev-guide
mirror of https://github.com/rust-lang/rustc-dev-guide.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Review changes

This commit is contained in:
Jakub Beránek 2023-09-05 16:34:37 +02:00 committed by Tshepang Mbambo
parent 665bd2cdcc
commit 3b0eb4cd62
1 changed files with 11 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
src/building/optimized-build.md
View File

@ -22,7 +22,7 @@ lto = "thin"
> Note that LTO for `rustc` is currently supported and tested only for > Note that LTO for `rustc` is currently supported and tested only for
> the `x86_64-unknown-linux-gnu` target. Other targets *may* work, but no guarantees are provided. > the `x86_64-unknown-linux-gnu` target. Other targets *may* work, but no guarantees are provided.
> Notably, LTO optimized `rustc` currently produces [miscompilations] on Windows. > Notably, LTO-optimized `rustc` currently produces [miscompilations] on Windows.
[miscompilations]: https://github.com/rust-lang/rust/issues/109114 [miscompilations]: https://github.com/rust-lang/rust/issues/109114
@ -63,7 +63,7 @@ compile `rustc` for a specific instruction set architecture, you can set the `ta
option in `RUSTFLAGS`: option in `RUSTFLAGS`:
```bash ```bash
$ RUSTFLAGS="-C target_cpu=x86-64-v3" x.py build ... RUSTFLAGS="-C target_cpu=x86-64-v3" ./x build ...
``` ```
If you also want to compile LLVM for a specific instruction set, you can set `llvm` flags If you also want to compile LLVM for a specific instruction set, you can set `llvm` flags
@ -78,9 +78,9 @@ cflags = "-march=x86-64-v3"
## Profile-guided optimization ## Profile-guided optimization
Applying profile-guided optimizations (or more generally, feedback-directed optimizations) can Applying profile-guided optimizations (or more generally, feedback-directed optimizations) can
produce a large increase to `rustc` performance, by up to 25%. However, these techniques are not produce a large increase to `rustc` performance, by up to 15% ([1], [2]). However, these techniques
simply enabled by a configuration option, but rather they require a complex build workflow that are not simply enabled by a configuration option, but rather they require a complex build workflow
compiles `rustc` multiple times and profiles it on selected benchmarks. that compiles `rustc` multiple times and profiles it on selected benchmarks.
There is a tool called `opt-dist` that is used to optimize `rustc` with [PGO] (profile-guided There is a tool called `opt-dist` that is used to optimize `rustc` with [PGO] (profile-guided
optimizations) and [BOLT] (a post-link binary optimizer) for builds distributed to end users. You optimizations) and [BOLT] (a post-link binary optimizer) for builds distributed to end users. You
@ -89,6 +89,9 @@ workflow based on it, or try to use it directly. Note that the tool is currently
the way we use it in Rust's continuous integration workflows, and it might require some custom the way we use it in Rust's continuous integration workflows, and it might require some custom
changes to make it work in a different environment. changes to make it work in a different environment.
[1]: https://blog.rust-lang.org/inside-rust/2020/11/11/exploring-pgo-for-the-rust-compiler.html#final-numbers-and-a-benchmarking-plot-twist
[2]: https://github.com/rust-lang/rust/pull/96978
[PGO]: https://doc.rust-lang.org/rustc/profile-guided-optimization.html [PGO]: https://doc.rust-lang.org/rustc/profile-guided-optimization.html
[BOLT]: https://github.com/llvm/llvm-project/blob/main/bolt/README.md [BOLT]: https://github.com/llvm/llvm-project/blob/main/bolt/README.md
@ -112,11 +115,11 @@ you execute the following commands on a Linux system):
1. Build the tool with the following command: 1. Build the tool with the following command:
```bash ```bash
$ python3 x.py build tools/opt-dist ./x build tools/opt-dist
``` ```
2. Run the tool with the `PGO_HOST` environment variable set to the 64-bit Linux target: 2. Run the tool with the `PGO_HOST` environment variable set to the 64-bit Linux target:
```bash ```bash
$ PGO_HOST=x86_64-unknown-linux-gnu ./build/host/stage0-tools-bin/opt-dist PGO_HOST=x86_64-unknown-linux-gnu ./build/host/stage0-tools-bin/opt-dist
``` ```
Note that the default Linux environment expects several hardcoded paths to exist: Note that the default Linux environment expects several hardcoded paths to exist:
- `/checkout` should contain a checkout of the Rust compiler repository that will be compiled. - `/checkout` should contain a checkout of the Rust compiler repository that will be compiled.
@ -126,6 +129,6 @@ you execute the following commands on a Linux system):
You can modify `LinuxEnvironment` (or implement your own) to override these paths. You can modify `LinuxEnvironment` (or implement your own) to override these paths.
[`Environment`]: https://github.com/rust-lang/rust/blob/65e468f9c259749c210b1ae8972bfe14781f72f1/src/tools/opt-dist/src/environment/mod.rs#L8-L7 [`Environment`]: https://github.com/rust-lang/rust/blob/65e468f9c259749c210b1ae8972bfe14781f72f1/src/tools/opt-dist/src/environment/mod.rs#L8-L70
[Rust benchmark suite]: https://github.com/rust-lang/rustc-perf [Rust benchmark suite]: https://github.com/rust-lang/rustc-perf