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remove redundant backchain attribute in codegen

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llvm will look at both
1. the values of "target-features" and
2. the function string attributes.

this removes the redundant function string attribute because it is not needed at all.
rustc sets the `+backchain` attribute through `target_features_attr(...)`
This commit is contained in:
Eddy (Eduard) Stefes 2026-02-11 10:19:50 +01:00
parent f21b4c0888
commit c6f57becfc
2 changed files with 15 additions and 14 deletions
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14
compiler/rustc_codegen_llvm/src/attributes.rs
View file

@ -301,17 +301,6 @@ fn stackprotector_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> Option<&'ll A
Some(sspattr.create_attr(cx.llcx))
}
fn backchain_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> Option<&'ll Attribute> {
if sess.target.arch != Arch::S390x {
return None;
}
let requested_features = sess.opts.cg.target_feature.split(',');
let found_positive = requested_features.clone().any(|r| r == "+backchain");
if found_positive { Some(llvm::CreateAttrString(cx.llcx, "backchain")) } else { None }
}
pub(crate) fn target_cpu_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> &'ll Attribute {
let target_cpu = llvm_util::target_cpu(sess);
llvm::CreateAttrStringValue(cx.llcx, "target-cpu", target_cpu)
@ -530,9 +519,6 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
if let Some(align) = codegen_fn_attrs.alignment {
llvm::set_alignment(llfn, align);
}
if let Some(backchain) = backchain_attr(cx, sess) {
to_add.push(backchain);
}
to_add.extend(patchable_function_entry_attrs(
cx,
sess,

15
tests/codegen-llvm/backchain.rs Normal file
View file

@ -0,0 +1,15 @@
//@ add-minicore
//@ compile-flags: -Copt-level=3 --crate-type=lib --target=s390x-unknown-linux-gnu -Ctarget-feature=+backchain
//@ needs-llvm-components: systemz
#![crate_type = "lib"]
#![feature(no_core, lang_items)]
#![no_core]
extern crate minicore;
use minicore::*;
#[no_mangle]
pub fn test_backchain() {
// CHECK: @test_backchain() unnamed_addr #0
}
// CHECK: attributes #0 = { {{.*}}"target-features"="{{[^"]*}}+backchain{{.*}} }