rust/compiler/rustc_codegen_llvm
Jubilee 6c2d4bf3f7
Rollup merge of #87918 - mikebenfield:pr-afdo, r=nikic
Enable AutoFDO.

This largely involves implementing the options debug-info-for-profiling
and profile-sample-use and forwarding them on to LLVM.

AutoFDO can be used on x86-64 Linux like this:
rustc -O -Clink-arg='Wl,--no-rosegment' -Cdebug-info-for-profiling main.rs -o main
perf record -b ./main
create_llvm_prof --binary=main --out=code.prof
rustc -O -Cprofile-sample-use=code.prof main.rs -o main2

Now `main2` will have feedback directed optimization applied to it.

The create_llvm_prof tool can be obtained from this github repository:
https://github.com/google/autofdo

The option -Clink-arg='Wl,--no-rosegment' is necessary to avoid lld
putting an extra RO segment before the executable code, which would make
the binary silently incompatible with create_llvm_prof.
2021-10-07 20:26:09 -07:00
..
src Rollup merge of #87918 - mikebenfield:pr-afdo, r=nikic 2021-10-07 20:26:09 -07:00
Cargo.toml Remove re-export. 2021-10-03 16:08:54 +02:00
README.md mv compiler to compiler/ 2020-08-30 18:45:07 +03:00

The codegen crate contains the code to convert from MIR into LLVM IR, and then from LLVM IR into machine code. In general it contains code that runs towards the end of the compilation process.

For more information about how codegen works, see the rustc dev guide.