https://bugs.llvm.org/show_bug.cgi?id=45723
Bug ID: 45723
Summary: Failure to optimize out useless zero-ing after
register was already zero-ed
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: gabrav...@gmail.com
CC: craig.top...@gmail.com, llvm-bugs@lists.llvm.org,
llvm-...@redking.me.uk, spatel+l...@rotateright.com
int f(bool b, int *p)
{
return b && *p;
}
LLVM generates this with -O3 :
f(bool, int*): # @f(bool, int*)
xor eax, eax ; Note that eax is zero-ed here
test dil, dil
je .LBB0_2
xor eax, eax ; Zero-ing eax here is thus useless
cmp dword ptr [rsi], 0
setne al
.LBB0_2:
ret
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