diff options
Diffstat (limited to 'compiler/rustc_codegen_llvm')
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/lib.rs | 4 | ||||
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/llvm_util.rs | 115 |
2 files changed, 60 insertions, 59 deletions
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs index 2f3c8c75b0b..f622646a5d9 100644 --- a/compiler/rustc_codegen_llvm/src/lib.rs +++ b/compiler/rustc_codegen_llvm/src/lib.rs @@ -340,8 +340,8 @@ impl CodegenBackend for LlvmCodegenBackend { llvm_util::print_version(); } - fn target_features_cfg(&self, sess: &Session, allow_unstable: bool) -> Vec<Symbol> { - target_features_cfg(sess, allow_unstable) + fn target_features_cfg(&self, sess: &Session) -> (Vec<Symbol>, Vec<Symbol>) { + target_features_cfg(sess) } fn codegen_crate<'tcx>( diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs index 5cc4f4ab9e6..4a166b0872d 100644 --- a/compiler/rustc_codegen_llvm/src/llvm_util.rs +++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs @@ -306,45 +306,44 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea /// Must express features in the way Rust understands them. /// /// We do not have to worry about RUSTC_SPECIFIC_FEATURES here, those are handled outside codegen. -pub(crate) fn target_features_cfg(sess: &Session, allow_unstable: bool) -> Vec<Symbol> { - let mut features: FxHashSet<Symbol> = Default::default(); - +pub(crate) fn target_features_cfg(sess: &Session) -> (Vec<Symbol>, Vec<Symbol>) { // Add base features for the target. // We do *not* add the -Ctarget-features there, and instead duplicate the logic for that below. // The reason is that if LLVM considers a feature implied but we do not, we don't want that to // show up in `cfg`. That way, `cfg` is entirely under our control -- except for the handling of - // the target CPU, that is still expanded to target features (with all their implied features) by - // LLVM. + // the target CPU, that is still expanded to target features (with all their implied features) + // by LLVM. let target_machine = create_informational_target_machine(sess, true); - // Compute which of the known target features are enabled in the 'base' target machine. - // We only consider "supported" features; "forbidden" features are not reflected in `cfg` as of now. - features.extend( - sess.target - .rust_target_features() - .iter() - .filter(|(feature, _, _)| { - // skip checking special features, as LLVM may not understand them - if RUSTC_SPECIAL_FEATURES.contains(feature) { - return true; - } - // check that all features in a given smallvec are enabled - if let Some(feat) = to_llvm_features(sess, feature) { - for llvm_feature in feat { - let cstr = SmallCStr::new(llvm_feature); - if !unsafe { llvm::LLVMRustHasFeature(target_machine.raw(), cstr.as_ptr()) } - { - return false; - } + // Compute which of the known target features are enabled in the 'base' target machine. We only + // consider "supported" features; "forbidden" features are not reflected in `cfg` as of now. + let mut features: FxHashSet<Symbol> = sess + .target + .rust_target_features() + .iter() + .filter(|(feature, _, _)| { + // skip checking special features, as LLVM may not understand them + if RUSTC_SPECIAL_FEATURES.contains(feature) { + return true; + } + if let Some(feat) = to_llvm_features(sess, feature) { + for llvm_feature in feat { + let cstr = SmallCStr::new(llvm_feature); + // `LLVMRustHasFeature` is moderately expensive. On targets with many + // features (e.g. x86) these calls take a non-trivial fraction of runtime + // when compiling very small programs. + if !unsafe { llvm::LLVMRustHasFeature(target_machine.raw(), cstr.as_ptr()) } { + return false; } - true - } else { - false } - }) - .map(|(feature, _, _)| Symbol::intern(feature)), - ); + true + } else { + false + } + }) + .map(|(feature, _, _)| Symbol::intern(feature)) + .collect(); - // Add enabled features + // Add enabled and remove disabled features. for (enabled, feature) in sess.opts.cg.target_feature.split(',').filter_map(|s| match s.chars().next() { Some('+') => Some((true, Symbol::intern(&s[1..]))), @@ -360,7 +359,7 @@ pub(crate) fn target_features_cfg(sess: &Session, allow_unstable: bool) -> Vec<S #[allow(rustc::potential_query_instability)] features.extend( sess.target - .implied_target_features(std::iter::once(feature.as_str())) + .implied_target_features(feature.as_str()) .iter() .map(|s| Symbol::intern(s)), ); @@ -371,11 +370,7 @@ pub(crate) fn target_features_cfg(sess: &Session, allow_unstable: bool) -> Vec<S // `features.contains` below. #[allow(rustc::potential_query_instability)] features.retain(|f| { - if sess - .target - .implied_target_features(std::iter::once(f.as_str())) - .contains(&feature.as_str()) - { + if sess.target.implied_target_features(f.as_str()).contains(&feature.as_str()) { // If `f` if implies `feature`, then `!feature` implies `!f`, so we have to // remove `f`. (This is the standard logical contraposition principle.) false @@ -387,25 +382,31 @@ pub(crate) fn target_features_cfg(sess: &Session, allow_unstable: bool) -> Vec<S } } - // Filter enabled features based on feature gates - sess.target - .rust_target_features() - .iter() - .filter_map(|(feature, gate, _)| { - // The `allow_unstable` set is used by rustc internally to determined which target - // features are truly available, so we want to return even perma-unstable "forbidden" - // features. - if allow_unstable - || (gate.in_cfg() && (sess.is_nightly_build() || gate.requires_nightly().is_none())) - { - Some(*feature) - } else { - None - } - }) - .filter(|feature| features.contains(&Symbol::intern(feature))) - .map(|feature| Symbol::intern(feature)) - .collect() + // Filter enabled features based on feature gates. + let f = |allow_unstable| { + sess.target + .rust_target_features() + .iter() + .filter_map(|(feature, gate, _)| { + // The `allow_unstable` set is used by rustc internally to determined which target + // features are truly available, so we want to return even perma-unstable + // "forbidden" features. + if allow_unstable + || (gate.in_cfg() + && (sess.is_nightly_build() || gate.requires_nightly().is_none())) + { + Some(Symbol::intern(feature)) + } else { + None + } + }) + .filter(|feature| features.contains(&feature)) + .collect() + }; + + let target_features = f(false); + let unstable_target_features = f(true); + (target_features, unstable_target_features) } pub(crate) fn print_version() { @@ -682,7 +683,7 @@ pub(crate) fn global_llvm_features( for feature in sess.opts.cg.target_feature.split(',') { if let Some(feature) = feature.strip_prefix('+') { all_rust_features.extend( - UnordSet::from(sess.target.implied_target_features(std::iter::once(feature))) + UnordSet::from(sess.target.implied_target_features(feature)) .to_sorted_stable_ord() .iter() .map(|&&s| (true, s)), |