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  1. 14 Oct, 2020 7 commits
  3. 13 Oct, 2020 31 commits
  5. 12 Oct, 2020 2 commits
    • Ng Zhi An's avatar
      [wasm-simd] Guard i64x2 widen i32x4 behind post-mvp flag · 62a16f14
      Ng Zhi An authored 
      These are still not in proposal, so they should be behind the post-mvp
flag.

Bug: v8:10972
Change-Id: I1b53307f334ddd8e21a095c13d7f7abb8ce05203
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2465654
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: 's avatarBill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70463}
      62a16f14
    • Ng Zhi An's avatar
      [wasm-simd][x64] Don't force dst to be same as src on AVX · 813ae013
      Ng Zhi An authored 
      On AVX, many instructions can have 3 operands, unlike SSE which only has
2. So on SSE we use DefineSameAsFirst on the dst. But on AVX, using that
will cause some unnecessary moves.

This patch changes a couple of F32x4 and S128 instructions to remove
this restriction when AVX is supported.

We can't use AvxHelper since it duplicates the dst for the call to the
AVX instruction, which isn't what we want. The alternative is to
redefine Mulps and other functions here, but there are other callsites
that depend on this duplicated-dst behavior, so it's harder to change.
We can migrate this as we move more logic over to non-DefineSameAsFirst
for AVX.

With the meshopt_decoder.js in the linked bug, it removes 8 SIMD movs
(from a function that has 300+ lines of assembly.)

Note that from agner's microarchitecture.pdf, page 127, "Elimination of
move instructions", many times such moves can be eliminated by the
processor. So this change won't speed up perf, but it helps a bit with
binary size, and decoder pressure.

Bug: v8:10116,v8:9561
Change-Id: I125bfd44e728ef08312620bc00f6433f376e69e3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2465653Reviewed-by: 's avatarBill Budge <bbudge@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70462}
      813ae013