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Rollup merge of #129940 - liushuyu:s390x-target-features, r=RalfJung

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s390x: Fix a regression related to backchain feature

In #127506, we introduced a new IBM Z-specific target feature, `backchain`.

This particular `target-feature` was available as a function-level attribute in LLVM 17 and below, so some hacks were used to avoid blowing up LLVM when querying the supported LLVM features.

This led to an unfortunate regression where `cfg!(target-feature = "backchain")` will always return true.

This pull request aims to fix this issue, and a test has been introduced to ensure it will never happen again.

Fixes #129927.

r? `@RalfJung`
This commit is contained in:
Michael Goulet 2024-09-07 14:21:22 +03:00 committed by GitHub
commit bc2244f027
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2 changed files with 47 additions and 3 deletions
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4
compiler/rustc_codegen_llvm/src/llvm_util.rs
View File

@ -353,9 +353,7 @@ pub fn target_features(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
None
}
})
.filter(|feature| {
RUSTC_SPECIAL_FEATURES.contains(feature) || features.contains(&Symbol::intern(feature))
})
.filter(|feature| features.contains(&Symbol::intern(feature)))
.map(|feature| Symbol::intern(feature))
.collect()
}

46
tests/assembly/s390x-backchain-toggle.rs Normal file
View File

@ -0,0 +1,46 @@
//@ revisions: enable-backchain disable-backchain
//@ assembly-output: emit-asm
//@ compile-flags: -O --crate-type=lib --target=s390x-unknown-linux-gnu
//@ needs-llvm-components: systemz
//@[enable-backchain] compile-flags: -Ctarget-feature=+backchain
//@[disable-backchain] compile-flags: -Ctarget-feature=-backchain
#![feature(no_core, lang_items)]
#![no_std]
#![no_core]
#[lang = "sized"]
trait Sized {}
extern "C" {
fn extern_func();
}
// CHECK-LABEL: test_backchain
#[no_mangle]
extern "C" fn test_backchain() -> i32 {
// Here we try to match if backchain register is saved to the parameter area (stored in r15/sp)
// And also if a new parameter area (160 bytes) is allocated for the upcoming function call
// enable-backchain: lgr [[REG1:.*]], %r15
// enable-backchain-NEXT: aghi %r15, -160
// enable-backchain: stg [[REG1]], 0(%r15)
// disable-backchain: aghi %r15, -160
// disable-backchain-NOT: stg %r{{.*}}, 0(%r15)
unsafe {
extern_func();
}
// enable-backchain-NEXT: brasl %r{{.*}}, extern_func@PLT
// disable-backchain: brasl %r{{.*}}, extern_func@PLT
// Make sure that the expected return value is written into %r2 (return register):
// enable-backchain-NEXT: lghi %r2, 1
// disable-backchain: lghi %r2, 0
#[cfg(target_feature = "backchain")]
{
1
}
#[cfg(not(target_feature = "backchain"))]
{
0
}
// CHECK: br %r{{.*}}
}