Remove xbegin and _xend

[DKLoehr]

intrin.h contains declarations for both xbegin and _xend, but they should already be included transitively from rtmintrin.h via immintrin.h and/or x86intrin.h. Having them in both places causes problems if both headers are included.

Furthermore, the intrin.h declaration of xbegin seems to be bugged anyway, since it's missing its leading underscore.

Fixes #95133

[llvmbot]

@llvm/pr-subscribers-backend-x86

@llvm/pr-subscribers-clang

Author: Devon Loehr (DKLoehr)

Changes

intrin.h contains declarations for both xbegin and _xend, but they should already be included transitively from rtmintrin.h via immintrin.h and/or x86intrin.h. Having them in both places causes problems if both headers are included.

Furthermore, the intrin.h declaration of xbegin seems to be bugged anyway, since it's missing its leading underscore.

Fixes #95133

---

Full diff: https://github.com/llvm/llvm-project/pull/126952.diff

1 Files Affected:

• (modified) clang/lib/Headers/intrin.h (-2)

diff --git a/clang/lib/Headers/intrin.h b/clang/lib/Headers/intrin.h
index 376046aeeaf5e..3dd1eb45817d4 100644
--- a/clang/lib/Headers/intrin.h
+++ b/clang/lib/Headers/intrin.h
@@ -162,8 +162,6 @@ void _Store_HLERelease(long volatile *, long);
 void _Store64_HLERelease(__int64 volatile *, __int64);
 void _StorePointer_HLERelease(void *volatile *, void *);
 void _WriteBarrier(void);
-unsigned __int32 xbegin(void);
-void _xend(void);
 
 /* These additional intrinsics are turned on in x64/amd64/x86_64 mode. */
 #if defined(__x86_64__) && !defined(__arm64ec__)

[rnk]

This is an observable behavior change, so it should have a test. There's a test for this header at clang/test/Headers/ms-intrins.cpp that you can extend. You probably need to add a new RUN line that adds -mrtm or some other micro-architectural feature so that rtmintrin.h declares _xend and you observe the redeclaration error reported in #95133.

[DKLoehr]

Added a test based on the linked bug. I couldn't get it to reproduce in anything that seemed to fit in the existing file, so I made a new one.

[rnk]

Thanks!

[DKLoehr]

Just checking in, this was approved a few days ago but hasn't been merged yet.

[glandium]

Should this be uplifted to release/20.x?
Cc: @tstellar