------- Comment #7 from uros at kss-loka dot si 2006-09-05 13:43 -------
Hm, proposed patch now generates worse code for following test:
extern int fnc1(void);
extern int fnc2(void);
int test(int x)
{
if (x & 0x02)
return fnc1();
else if (x & 0x01)
return fnc2();
else
return 0;
}
It generates:
test:
movl 4(%esp), %edx
movl %edx, %eax
andl $2, %eax
jne .L10
andl $1, %edx
jne .L11
xorl %eax, %eax
ret
.p2align 4,,7
.L11:
.p2align 4,,8
jmp fnc2
.p2align 4,,7
.L10:
.p2align 4,,7
jmp fnc1
due to marking %eax live in first comparison, "and" is used instead of "test",
and a regmove is emitted before comparison. Ideally gcc should generate:
test:
movl 4(%esp), %eax
testl $2, %eax
jne .L6
andl $1, %eax
jne .L7
xorl %eax, %eax
ret
.p2align 2,,3
.L7:
jmp fnc2
.p2align 2,,3
.L6:
jmp fnc1
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28946
