bjoernager/rust
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Auto merge of #137586 - nnethercote:SetImpliedBits, r=bjorn3

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Speed up target feature computation

The LLVM backend calls `LLVMRustHasFeature` twice for every feature. In short-running rustc invocations, this accounts for a surprising amount of work.

r? `@bjorn3`
This commit is contained in:
bors 2025-03-11 12:05:16 +00:00
commit ebf0cf75d3
9 changed files with 120 additions and 113 deletions
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2
compiler/rustc_codegen_ssa/src/target_features.rs
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@ -190,7 +190,7 @@ pub(crate) fn provide(providers: &mut Providers) {
},
implied_target_features: |tcx, feature: Symbol| {
let feature = feature.as_str();
UnordSet::from(tcx.sess.target.implied_target_features(std::iter::once(feature)))
UnordSet::from(tcx.sess.target.implied_target_features(feature))
.into_sorted_stable_ord()
.into_iter()
.map(|s| Symbol::intern(s))

9
compiler/rustc_codegen_ssa/src/traits/backend.rs
View file

@ -45,10 +45,13 @@ pub trait CodegenBackend {
fn print(&self, _req: &PrintRequest, _out: &mut String, _sess: &Session) {}
/// Returns the features that should be set in `cfg(target_features)`.
/// Returns two feature sets:
/// - The first has the features that should be set in `cfg(target_features)`.
/// - The second is like the first, but also includes unstable features.
///
/// RUSTC_SPECIFIC_FEATURES should be skipped here, those are handled outside codegen.
fn target_features_cfg(&self, _sess: &Session, _allow_unstable: bool) -> Vec<Symbol> {
vec![]
fn target_features_cfg(&self, _sess: &Session) -> (Vec<Symbol>, Vec<Symbol>) {
(vec![], vec![])
}
fn print_passes(&self) {}