https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127617
Bug ID: 127617
Summary: convert double comparison to difference or the other
way around
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: manu at gcc dot gnu.org
Target Milestone: ---
https://godbolt.org/z/ozoh3Y46G
I am not sure which option is faster, but _2 and _3 should produce the same
code, no? (whatever code is faster)
```
#include <stdbool.h>
bool
dominates_2d(const double * restrict a, const double * restrict b)
{
return a[0] <= b[0] && a[1] <= b[1] && (a[0] != b[0] || a[1] != b[1]);
}
bool
dominates_2d_2(const double * restrict a, const double * restrict b)
{
return (a[0] <= b[0]) & (a[1] <= b[1]) & (a[0] != b[0] || a[1] != b[1]);
}
bool
dominates_2d_3(const double * restrict a, const double * restrict b)
{
const double diff0 = b[0] - a[0];
const double diff1 = b[1] - a[1];
return (diff0 >= 0) & (diff1 >= 0) & ((diff0 != 0) || (diff1 != 0));
}
```
Compile with: -Wall -Wpedantic -Wextra -O3 -march=x86-64-v2 -ffast-math
produces:
"dominates_2d":
movsd xmm1, QWORD PTR [rdi]
movsd xmm0, QWORD PTR [rsi]
comisd xmm0, xmm1
jb .L4
movsd xmm3, QWORD PTR [rdi+8]
movsd xmm2, QWORD PTR [rsi+8]
comisd xmm2, xmm3
jb .L4
comisd xmm3, xmm2
setne al
comisd xmm1, xmm0
setne dl
or eax, edx
ret
.L4:
xor eax, eax
ret
"dominates_2d_2":
movsd xmm1, QWORD PTR [rdi]
movsd xmm0, QWORD PTR [rsi]
movsd xmm3, QWORD PTR [rdi+8]
movsd xmm2, QWORD PTR [rsi+8]
comisd xmm0, xmm1
setnb al
comisd xmm2, xmm3
setnb dl
and eax, edx
comisd xmm3, xmm2
setne dl
comisd xmm1, xmm0
setne cl
or edx, ecx
and eax, edx
ret
"dominates_2d_3":
movsd xmm2, QWORD PTR [rsi]
subsd xmm2, QWORD PTR [rdi]
pxor xmm0, xmm0
movsd xmm1, QWORD PTR [rsi+8]
subsd xmm1, QWORD PTR [rdi+8]
comisd xmm2, xmm0
setnb al
comisd xmm1, xmm0
setnb dl
and eax, edx
comisd xmm2, xmm0
setne dl
comisd xmm1, xmm0
setne cl
or edx, ecx
and eax, edx
ret
