On Wed, Sep 2, 2026 at 11:01 PM Roger Sayle <[email protected]> wrote:
>
>
> vpinsrb $1, %esi, %xmm0, %xmm0
> vpbroadcastw %xmm0, %xmm0
> ret
>
> bar: vmovdqa .LC0(%rip), %xmm0
> vpinsrb $0, %edi, %xmm0, %xmm0
> vpinsrb $8, %edi, %xmm0, %xmm0
> ret
>
> There's still more that can be done/improved, but I stopped here
> (1) because the patch is already quite large and (2) I'm not sure
> if the final bar above is optimal (yes in number of instructions),
> or if (v2di){0x12345678abcdefLL,0} is better written as movabs+movq?
We can stop here until we find real opportunity in real workload.
>+ for (i = 0; i < 4; i++)
>+ if (CONST_INT_P (ops[i]) && ops[i] != const0_rtx)
>+ {
>+ val += (UINTVAL (ops[0]) & 0xff) << (i*8);
typo, should be ops[i], not ops[0]?
>+ vars[i] = const0_rtx;
>+ }
>+ bool all_same_p = true;
>+ for (i = 1; i < 16; i++)
>+ if (!rtx_equal_p (ops[i], ops[0]))
>+ {
>+ all_same_p = false;
>+ break;
>+ }
>+ if (all_same_p)
We already handle all_same_p in ix86_expand_vector_init before it
reaches _general, and I didn't see any place with recursively call
which needs to handle all_same_p, so perhaps just remove the code for
all_same_p.
>+ {
>+ ok = ix86_expand_vector_init_duplicate (false, V16QImode,
>+ target, ops[0]);
>+ gcc_assert (ok);
>+ return;
>+ }
--
BR,
Hongtao
