| Issue |
154554
|
| Summary |
[RISCV][LV] Subtract in reduction forcing fixed vector codegen
|
| Labels |
vectorizers
|
| Assignees |
|
| Reporter |
preames
|
In the following example, we have a summation loop. One of the terms being contributed to the accumulator involves a subtraction. This "-" appears to force us to pick a fixed vectorization factor instead of a scalable one. Simply changing the "-" to a "+" results in a scalable vector factor being chosen.
```
typedef struct {
int x;
} s_t;
int example(s_t *a, s_t *b, int len) {
int accum = 0;
for (int i = 0; i < len; ++i) {
accum += a[i].x - b[i].x;
;
}
return accum;
}
```
My guess is that this is some quirk of our cost model. I haven't tried to chase it down just yet.
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