rustc: Support Rust-specific features in -Ctarget-feature #84991
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Since the beginning of time the `-Ctarget-feature` flag on the command
line has largely been passed unmodified to LLVM. Afterwards, though, the
`#[target_feature]` attribute was stabilized and some of the names in
this attribute do not match the corresponding LLVM name. This is because
Rust doesn't always want to stabilize the exact feature name in LLVM for
the equivalent functionality in Rust. This creates a situation, however,
where in Rust you'd write:
#[target_feature(enable = "pclmulqdq")]
unsafe fn foo() {
// ...
}
but on the command line you would write:
RUSTFLAGS="-Ctarget-feature=+pclmul" cargo build --release
This difference is somewhat odd to deal with if you're a newcomer and
the situation may be made worse with upcoming features like [WebAssembly
SIMD](rust-lang#74372) which may be more
prevalent.
This commit implements a mapping to translate requests via
`-Ctarget-feature` through the same name-mapping functionality that's
present for attributes in Rust going to LLVM. This means that
`+pclmulqdq` will work on x86 targets where as previously it did not.
I've attempted to keep this backwards-compatible where the compiler will
just opportunistically attempt to remap features found in
`-Ctarget-feature`, but if there's something it doesn't understand it
gets passed unmodified to LLVM just as it was before.
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| let feature = if s.starts_with("+") || s.starts_with("-") { | ||
| &s[1..] | ||
| } else { | ||
| return Some(s.to_string()); |
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Curious that we accept target features without a leading + without complaining (like we'd otherwise do for unknown features), but they don't have any particular effect, either.
|
@bors r+ |
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📌 Commit 97658e5 has been approved by |
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…r=nagisa
rustc: Support Rust-specific features in -Ctarget-feature
Since the beginning of time the `-Ctarget-feature` flag on the command
line has largely been passed unmodified to LLVM. Afterwards, though, the
`#[target_feature]` attribute was stabilized and some of the names in
this attribute do not match the corresponding LLVM name. This is because
Rust doesn't always want to stabilize the exact feature name in LLVM for
the equivalent functionality in Rust. This creates a situation, however,
where in Rust you'd write:
#[target_feature(enable = "pclmulqdq")]
unsafe fn foo() {
// ...
}
but on the command line you would write:
RUSTFLAGS="-Ctarget-feature=+pclmul" cargo build --release
This difference is somewhat odd to deal with if you're a newcomer and
the situation may be made worse with upcoming features like [WebAssembly
SIMD](rust-lang#74372) which may be more
prevalent.
This commit implements a mapping to translate requests via
`-Ctarget-feature` through the same name-mapping functionality that's
present for attributes in Rust going to LLVM. This means that
`+pclmulqdq` will work on x86 targets where as previously it did not.
I've attempted to keep this backwards-compatible where the compiler will
just opportunistically attempt to remap features found in
`-Ctarget-feature`, but if there's something it doesn't understand it
gets passed unmodified to LLVM just as it was before.
Dylan-DPC-zz
pushed a commit
to Dylan-DPC-zz/rust
that referenced
this pull request
May 7, 2021
…r=nagisa
rustc: Support Rust-specific features in -Ctarget-feature
Since the beginning of time the `-Ctarget-feature` flag on the command
line has largely been passed unmodified to LLVM. Afterwards, though, the
`#[target_feature]` attribute was stabilized and some of the names in
this attribute do not match the corresponding LLVM name. This is because
Rust doesn't always want to stabilize the exact feature name in LLVM for
the equivalent functionality in Rust. This creates a situation, however,
where in Rust you'd write:
#[target_feature(enable = "pclmulqdq")]
unsafe fn foo() {
// ...
}
but on the command line you would write:
RUSTFLAGS="-Ctarget-feature=+pclmul" cargo build --release
This difference is somewhat odd to deal with if you're a newcomer and
the situation may be made worse with upcoming features like [WebAssembly
SIMD](rust-lang#74372) which may be more
prevalent.
This commit implements a mapping to translate requests via
`-Ctarget-feature` through the same name-mapping functionality that's
present for attributes in Rust going to LLVM. This means that
`+pclmulqdq` will work on x86 targets where as previously it did not.
I've attempted to keep this backwards-compatible where the compiler will
just opportunistically attempt to remap features found in
`-Ctarget-feature`, but if there's something it doesn't understand it
gets passed unmodified to LLVM just as it was before.
This was referenced May 7, 2021
bors
added a commit
to rust-lang-ci/rust
that referenced
this pull request
May 7, 2021
Rollup of 9 pull requests Successful merges: - rust-lang#84254 (illumos should put libc last in library search order) - rust-lang#84442 (Unify rustc and rustdoc parsing of `cfg()`) - rust-lang#84655 (Cleanup of `wasm`) - rust-lang#84866 (linker: Avoid library duplication with `/WHOLEARCHIVE`) - rust-lang#84930 (rename LLVM target for RustyHermit) - rust-lang#84991 (rustc: Support Rust-specific features in -Ctarget-feature) - rust-lang#85029 (SGX mutex is movable) - rust-lang#85030 (Rearrange SGX split module files) - rust-lang#85033 (some further small cleanups) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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Since the beginning of time the
-Ctarget-featureflag on the commandline has largely been passed unmodified to LLVM. Afterwards, though, the
#[target_feature]attribute was stabilized and some of the names inthis attribute do not match the corresponding LLVM name. This is because
Rust doesn't always want to stabilize the exact feature name in LLVM for
the equivalent functionality in Rust. This creates a situation, however,
where in Rust you'd write:
but on the command line you would write:
This difference is somewhat odd to deal with if you're a newcomer and
the situation may be made worse with upcoming features like WebAssembly
SIMD which may be more
prevalent.
This commit implements a mapping to translate requests via
-Ctarget-featurethrough the same name-mapping functionality that'spresent for attributes in Rust going to LLVM. This means that
+pclmulqdqwill work on x86 targets where as previously it did not.I've attempted to keep this backwards-compatible where the compiler will
just opportunistically attempt to remap features found in
-Ctarget-feature, but if there's something it doesn't understand itgets passed unmodified to LLVM just as it was before.