diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/doc/rustc/src/codegen-options/index.md | 20 | ||||
| -rw-r--r-- | src/test/codegen/tune-cpu-on-functions.rs | 21 |
2 files changed, 39 insertions, 2 deletions
diff --git a/src/doc/rustc/src/codegen-options/index.md b/src/doc/rustc/src/codegen-options/index.md index bed10ca16d3..f6493e49c3c 100644 --- a/src/doc/rustc/src/codegen-options/index.md +++ b/src/doc/rustc/src/codegen-options/index.md @@ -497,8 +497,10 @@ point instructions in software. It takes one of the following values: This instructs `rustc` to generate code specifically for a particular processor. You can run `rustc --print target-cpus` to see the valid options to pass -here. Additionally, `native` can be passed to use the processor of the host -machine. Each target has a default base CPU. +here. Each target has a default base CPU. Special values include: + +* `native` can be passed to use the processor of the host machine. +* `generic` refers to an LLVM target with minimal features but modern tuning. ## target-feature @@ -530,6 +532,20 @@ This also supports the feature `+crt-static` and `-crt-static` to control Each target and [`target-cpu`](#target-cpu) has a default set of enabled features. +## tune-cpu + +This instructs `rustc` to schedule code specifically for a particular +processor. This does not affect the compatibility (instruction sets or ABI), +but should make your code slightly more efficient on the selected CPU. + +The valid options are the same as those for [`target-cpu`](#target-cpu). +The default is `None`, which LLVM translates as the `target-cpu`. + +This is an unstable option. Use `-Z tune-cpu=machine` to specify a value. + +Due to limitations in LLVM (12.0.0-git9218f92), this option is currently +effective only for x86 targets. + [option-emit]: ../command-line-arguments.md#option-emit [option-o-optimize]: ../command-line-arguments.md#option-o-optimize [profile-guided optimization]: ../profile-guided-optimization.md diff --git a/src/test/codegen/tune-cpu-on-functions.rs b/src/test/codegen/tune-cpu-on-functions.rs new file mode 100644 index 00000000000..9121799cdbf --- /dev/null +++ b/src/test/codegen/tune-cpu-on-functions.rs @@ -0,0 +1,21 @@ +// This test makes sure that functions get annotated with the proper +// "tune-cpu" attribute in LLVM. + +// no-prefer-dynamic +// ignore-tidy-linelength +// compile-flags: -C no-prepopulate-passes -C panic=abort -C linker-plugin-lto -Cpasses=name-anon-globals -Z tune-cpu=generic + +#![crate_type = "staticlib"] + +// CHECK-LABEL: define {{.*}} @exported() {{.*}} #0 +#[no_mangle] +pub extern fn exported() { + not_exported(); +} + +// CHECK-LABEL: ; tune_cpu_on_functions::not_exported +// CHECK-NEXT: ; Function Attrs: +// CHECK-NEXT: define {{.*}}() {{.*}} #0 +fn not_exported() {} + +// CHECK: attributes #0 = {{.*}} "tune-cpu"="{{.*}}" |