https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85224
Bug ID: 85224
Summary: x86_64 missed optimisation opportunity for (-1 * !!x)
Product: gcc
Version: 8.0.1
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: vegard.nossum at oracle dot com
Target Milestone: ---
Input:
int f(int x) {
return -1 * !!x;
}
Trunk with -O3 gives:
f(int):
xor eax, eax
test edi, edi
setne al
neg eax
ret
While clang -O3 gives:
f: # @f
neg edi
sbb eax, eax
ret
gcc -O1 gives a different sequence which is slightly longer:
f(int):
test edi, edi
setne al
movzx eax, al
neg eax
ret
