Code like:

  x = wasm_v32x4_shuffle(x, x, 1, 2, 3, 0);

is currently matched by S8x16Concat, which lowers to two instructions:

  movapd xmm_dst, xmm_src
  palignr xmm_dst, xmm_src, 0x4

There is a special case after a S8x16Concat is matched:.

- is_swizzle, the inputs are the same
- it is a 32x4 shuffle (offset % 4 == 0)

Which can have a better codegen:

- (dst == src) shufps dst, src, 0b00111001
- (dst != src) pshufd dst, src, 0b00111001

Add a new simd shuffle matcher which will match 32x4 rotate, and
construct the appropriate indices referring to the 32x4 elements.

pshufd for the given example. However, this matching happens after
S8x16Concat, so we get the palignr first. We could move the pattern
matching cases around, but it will lead to some cases where
where it would have matched a S8x16Concat, but now matches a
S32x4shuffle instead, leading to worse codegen.

Note: we also pattern match on 32x4Swizzle, which correctly generates
Change-Id: Ie3aca53bbc06826be2cf49632de4c24ec73d0a9a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2589062Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71754}