https://bugs.llvm.org/show_bug.cgi?id=51745
Bug ID: 51745
Summary: LLVM 13 regression: lost transformation x < C && y < C
&& z < C to (x | y | z) < C
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: david.bolvan...@gmail.com
CC: llvm-bugs@lists.llvm.org
x < C && y < C && z < C to (x | y | z) < C where C is power of two.
bool
src1 (unsigned x, unsigned y, unsigned z, unsigned w)
{
return x < 1024 && y < 1024 && z < 1024 && w < 1024;
}
bool
tgt1 (unsigned x, unsigned y, unsigned z, unsigned w)
{
return (x | y | z | w) < 1024;
}
GCC:
src1(unsigned int, unsigned int, unsigned int, unsigned int):
or edx, ecx
or edx, esi
or edx, edi
cmp edx, 1023
setbe al
ret
tgt1(unsigned int, unsigned int, unsigned int, unsigned int):
or edx, ecx
or edx, esi
or edx, edi
cmp edx, 1023
setbe al
ret
Clang trunk:
src1(unsigned int, unsigned int, unsigned int, unsigned int):
# @src1(unsigned int, unsigned int, unsigned int, unsigned int)
cmp edi, 1024
setb al
cmp esi, 1024
setb sil
and sil, al
cmp edx, 1024
setb dl
cmp ecx, 1024
setb al
and al, dl
and al, sil
ret
tgt1(unsigned int, unsigned int, unsigned int, unsigned int):
# @tgt1(unsigned int, unsigned int, unsigned int, unsigned int)
or edi, esi
or edx, ecx
or edx, edi
cmp edx, 1024
setb al
ret
Regressed with LLVM 13 which disabled select-to-or optimization.
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