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rustc_codegen_llvm: properly passing backchain attribute to LLVM ...

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... this is a special attribute that was made to be a target-feature in
LLVM 18+, but in all previous versions, this "feature" is a naked
attribute. We will have to handle this situation differently than all
other target-features.
This commit is contained in:
liushuyu 2024-07-10 11:57:36 +08:00
parent 366bc8691b
commit 01e6e60bf3
3 changed files with 30 additions and 1 deletions
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14
compiler/rustc_codegen_llvm/src/llvm_util.rs
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@ -14,7 +14,7 @@ use rustc_session::config::{PrintKind, PrintRequest};
use rustc_session::Session;
use rustc_span::symbol::Symbol;
use rustc_target::spec::{MergeFunctions, PanicStrategy};
use rustc_target::target_features::RUSTC_SPECIFIC_FEATURES;
use rustc_target::target_features::{RUSTC_SPECIAL_FEATURES, RUSTC_SPECIFIC_FEATURES};
use std::ffi::{c_char, c_void, CStr, CString};
use std::fmt::Write;
@ -321,6 +321,10 @@ pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
}
})
.filter(|feature| {
// skip checking special features, as LLVM may not understands them
if RUSTC_SPECIAL_FEATURES.contains(feature) {
return true;
}
// check that all features in a given smallvec are enabled
for llvm_feature in to_llvm_features(sess, feature) {
let cstr = SmallCStr::new(llvm_feature);
@ -546,6 +550,7 @@ pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<Str
// -Ctarget-features
let supported_features = sess.target.supported_target_features();
let (llvm_major, _, _) = get_version();
let mut featsmap = FxHashMap::default();
let feats = sess
.opts
@ -604,6 +609,13 @@ pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<Str
if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
return None;
}
// if the target-feature is "backchain" and LLVM version is greater than 18
// then we also need to add "+backchain" to the target-features attribute.
// otherwise, we will only add the naked `backchain` attribute to the attribute-group.
if feature == "backchain" && llvm_major < 18 {
return None;
}
// ... otherwise though we run through `to_llvm_features` when
// passing requests down to LLVM. This means that all in-language
// features also work on the command line instead of having two