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[aarch64] add target feature outline-atomics

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Enable outline-atomics by default as enabled in clang by the following commit
https://reviews.llvm.org/rGc5e7e649d537067dec7111f3de1430d0fc8a4d11

Performance improves by several orders of magnitude when using the LSE instructions
instead of the ARMv8.0 compatible load/store exclusive instructions.

Tested on Graviton2 aarch64-linux with
x.py build && x.py install && x.py test
This commit is contained in:
Sebastian Pop 2021-04-05 17:17:23 +00:00
parent 3e8f32e1c5
commit 0f9f241aac
2 changed files with 21 additions and 0 deletions
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5
compiler/rustc_codegen_llvm/src/llvm_util.rs
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@ -416,6 +416,11 @@ pub fn llvm_global_features(sess: &Session) -> Vec<String> {
// -Ctarget-features
features.extend(sess.opts.cg.target_feature.split(',').flat_map(&filter));
// FIXME: Move outline-atomics to target definition when earliest supported LLVM is 12.
if get_version() >= (12, 0, 0) && sess.target.llvm_target.contains("aarch64-unknown-linux") {
features.push("+outline-atomics".to_string());
}
features
}