From 157137a64aeba7fb6e6571bcc046c97d63d368a7 Mon Sep 17 00:00:00 2001 From: Nicholas Nethercote Date: Tue, 25 Feb 2025 15:25:54 +1100 Subject: [PATCH] Change signature of `target_features_cfg`. Currently it is called twice, once with `allow_unstable` set to true and once with it set to false. This results in some duplicated work. Most notably, for the LLVM backend, `LLVMRustHasFeature` is called twice for every feature, and it's moderately slow. For very short running compilations on platforms with many features (e.g. a `check` build of hello-world on x86) this is a significant fraction of runtime. This commit changes `target_features_cfg` so it is only called once, and it now returns a pair of feature sets. This halves the number of `LLVMRustHasFeature` calls. --- src/lib.rs | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/src/lib.rs b/src/lib.rs index a3f43744875..06939beb374 100644 --- a/src/lib.rs +++ b/src/lib.rs @@ -176,13 +176,9 @@ impl CodegenBackend for CraneliftCodegenBackend { } } - fn target_features_cfg( - &self, - sess: &Session, - _allow_unstable: bool, - ) -> Vec { + fn target_features_cfg(&self, sess: &Session) -> (Vec, Vec) { // FIXME return the actually used target features. this is necessary for #[cfg(target_feature)] - if sess.target.arch == "x86_64" && sess.target.os != "none" { + let target_features = if sess.target.arch == "x86_64" && sess.target.os != "none" { // x86_64 mandates SSE2 support and rustc requires the x87 feature to be enabled vec![sym::fsxr, sym::sse, sym::sse2, Symbol::intern("x87")] } else if sess.target.arch == "aarch64" { @@ -196,7 +192,10 @@ impl CodegenBackend for CraneliftCodegenBackend { } } else { vec![] - } + }; + // FIXME do `unstable_target_features` properly + let unstable_target_features = target_features.clone(); + (target_features, unstable_target_features) } fn print_version(&self) {