https://bugs.llvm.org/show_bug.cgi?id=45149
Bug ID: 45149
Summary: Codegen being moved outside of volatile block
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Common Code Generator Code
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected],
[email protected], [email protected]
https://godbolt.org/z/bo6w2F
#include <x86intrin.h>
__v16qi foo(__v16qi a, __v16qi b) {
__asm volatile("# LLVM-MCA-BEGIN foo");
__v16qi result = a + b;
__asm volatile("# LLVM-MCA-END foo");
return result;
}
I'm seeing an issue where depending on the target cpu the generated asm is
getting moved out of the volatile comment block.
clang -g0 -O3:
# %bb.0:
#APP
# LLVM-MCA-BEGIN foo
#NO_APP
paddb %xmm1, %xmm0
#APP
# LLVM-MCA-END foo
#NO_APP
retq
clang -g0 -O3 -march=sandybridge:
# %bb.0:
#APP
# LLVM-MCA-BEGIN foo
#NO_APP
vpaddb %xmm0, %xmm1, %xmm0
#APP
# LLVM-MCA-END foo
#NO_APP
retq
clang -g0 -O3 -march=btver2:
# %bb.0:
vpaddb %xmm0, %xmm1, %xmm0
#APP
# LLVM-MCA-BEGIN foo
#NO_APP
#APP
# LLVM-MCA-END foo
#NO_APP
retq
which prevents llvm-mca from reporting on the code snippet.
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