| Issue |
71520
|
| Summary |
[AArch64] Missed fmla vectorisation opportunity (tsvc, s2275)
|
| Labels |
backend:AArch64,
vectorization
|
| Assignees |
|
| Reporter |
sjoerdmeijer
|
We are a lot behind (300%) for kernel s2275 in TSVC compared to GCC12.
Compile this input with {{}}:
```
__attribute__((aligned(64))) float a[32000],b[32000],c[32000],d[32000],e[32000],
aa[256][256],bb[256][256],cc[256][256],tt[256][256];
int dummy(float[32000], float[32000], float[32000], float[32000], float[32000], float[256][256], float[256][256], float[256][256], float);
float s2275(struct args_t * func_args)
{
for (int nl = 0; nl < 100*(100000/256); nl++) {
for (int i = 0; i < 256; i++) {
for (int j = 0; j < 256; j++) {
aa[j][i] = aa[j][i] + bb[j][i] * cc[j][i];
}
a[i] = b[i] + c[i] * d[i];
}
dummy(a, b, c, d, e, aa, bb, cc, 0.);
}
}
```
Clang's codegen:
```
.LBB0_2: // Parent Loop BB0_1 Depth=1
mov x12, xzr
.LBB0_3: // Parent Loop BB0_1 Depth=1
add x14, x10, x12
add x13, x9, x12
ldr s2, [x14]
ldr s3, [x14, #1024]
add x14, x11, x12
ldr s0, [x13]
ldr s1, [x13, #1024]
add x12, x12, #2048
ldr s4, [x14]
ldr s5, [x14, #1024]
cmp x12, #64, lsl #12 // =262144
fmadd s0, s4, s2, s0
fmadd s1, s5, s3, s1
str s0, [x13]
str s1, [x13, #1024]
b.ne .LBB0_3
ldr s0, [x22, x8, lsl #2]
ldr s1, [x23, x8, lsl #2]
ldr s2, [x24, x8, lsl #2]
add x11, x11, #4
add x10, x10, #4
add x9, x9, #4
fmadd s0, s2, s1, s0
str s0, [x25, x8, lsl #2]
add x8, x8, #1
cmp x8, #256
b.ne .LBB0_2
```
vs. GCC's codegen:
```
.L6:
mov x0, 0
.L3:
ldr q29, [x10, x0]
ldr q30, [x9, x0]
ldr q31, [x8, x0]
fmla v31.4s, v29.4s, v30.4s
str q31, [x8, x0]
add x0, x0, 1024
cmp x0, 262144
bne .L3
ldr q29, [x27, x11]
add x8, x8, 16
add x10, x10, 16
add x9, x9, 16
ldr q30, [x26, x11]
ldr q31, [x25, x11]
fmla v31.4s, v29.4s, v30.4s
str q31, [x19, x11]
add x11, x11, 16
cmp x11, 1024
bne .L6
```
See also:
https://godbolt.org/z/8E3fexn5o
TODO:
Root cause analysis.
![]()
_______________________________________________
llvm-bugs mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
