https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83123
Bug ID: 83123
Summary: Int compare - different asm code for different return
type
Product: gcc
Version: 7.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: bugzi...@poradnik-webmastera.com
Target Milestone: ---
int test1(int a, int b)
{
return (a < 0) && (b < 0);
}
bool test2(int a, int b)
{
return (a < 0) && (b < 0);
}
This produces following code, when compiled with -O2. For some reason 2nd
function performs shifts first, then and. This is not necessary, you can and
first, then shift. The same issue is for checking if any of numbers is negative
- or can be executed first, then shift.
test1(int, int):
and esi, edi
mov eax, esi
shr eax, 31
ret
test2(int, int):
mov eax, edi
shr esi, 31
shr eax, 31
and eax, esi
ret
