https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113034
Bug ID: 113034
Summary: Miscompilation of __m128 ne comparison on LoongArch
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: c at jia dot je
Target Milestone: ---
Compile and run the following code:
```
#include <lsxintrin.h>
#include <stdio.h>
__m128i unord_vec(__m128 a, __m128 b) { return (a != a) | (b != b); }
int unord_float(float a, float b) { return (a != a) | (b != b); }
int main() {
float nan = 0.0 / 0.0; // nan
__m128 nan_vec = {nan, nan};
int res_float = unord_float(nan, nan);
__m128i res_vec = unord_vec(nan_vec, nan_vec);
printf("%d %ld %ld\n", res_float, res_vec[0], res_vec[1]);
return 0;
}
```
Compile commands: `gcc-14 -mlsx test.c -O -o test`. GCC version is 14.0.0
202231203 snapshot.
It does the `unordered` comparison between two floats. The expected output:
```
1 1 1
```
Actual output:
```
1 0 0
```
Reading the assembly, the `unord_vec` is implemented wrongly as `vfcmp.cne.s`:
```
unord_vec:
.LFB538 = .
.cfi_startproc
vinsgr2vr.d $vr0,$r4,0
vinsgr2vr.d $vr0,$r5,1
vinsgr2vr.d $vr1,$r6,0
vinsgr2vr.d $vr1,$r7,1
vfcmp.cne.s $vr0,$vr0,$vr0
vfcmp.cne.s $vr1,$vr1,$vr1
vor.v $vr0,$vr0,$vr1
vpickve2gr.du $r4,$vr0,0
vpickve2gr.du $r5,$vr0,1
jr $r1
.cfi_endproc
```
Whereas `unord_float` is correctly implemented as `fcmp.cune.s`:
```
unord_float:
.LFB539 = .
.cfi_startproc
addi.w $r4,$r0,1 # 0x1
fcmp.cune.s $fcc0,$f0,$f0
bcnez $fcc0,.L3
or $r4,$r0,$r0
.L3:
addi.w $r12,$r0,1 # 0x1
fcmp.cune.s $fcc1,$f1,$f1
bcnez $fcc1,.L4
or $r12,$r0,$r0
.L4:
or $r4,$r4,$r12
andi $r4,$r4,1
jr $r1
.cfi_endproc
```
So there is a mismatch on the `unordered` case. Besides, these functions can be
optimized to use `vfcmp.cun.s` and `fcmp.cun.s`.
