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Rollup merge of #129940 - liushuyu:s390x-target-features, r=RalfJung
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`
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//@ 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] | ||
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#[lang = "sized"] | ||
trait Sized {} | ||
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extern "C" { | ||
fn extern_func(); | ||
} | ||
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// 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 | ||
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// 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{{.*}} | ||
} |