James Greenhalgh wrote:
>
> Have you tested this in cases where an integer dup is definitely the right
> thing to do?
Yes, this still generates:
#include <arm_neon.h>
void f(unsigned a, unsigned b, uint32x4_t *c)
{
c[0] = vdupq_n_u32(a);
c[1] = vdupq_n_u32(b);
}
dup v1.4s, w0
dup v0.4s, w1
str q1, [x2]
str q0, [x2, 16]
ret
The reason is that the GP to FP register move cost is typically >= 5, while
the additional cost of '?' is just 1.
> And similar cases? If these still look good, then the patch is OK - though
> I'm still very nervous about the register allocator cost model!
Well it's complex and hard to get working well... However slightly preferring
one
variant works alright (unlike using '*' which results in incorrect costs).
Wilco
