commit 1443c6920c4b7aa80811c30ed9cdc81395d5df4f
author mtklein <mtklein@chromium.org> Wed Mar 23 09:52:13 2016 -0700
committer Commit bot <commit-bot@chromium.org> Wed Mar 23 09:52:13 2016 -0700
tree efa88cb70147b55260017171c4ed903b90b6b8bb
parent ec950c4d215c6141b31b98ed6a8182a97baeb8b9

Sk4x4f: Simplify x86 down to SSE2.

  - This drops the minimum requirement for Sk4x4f on x86 to SSE2 by
    removing calls to _mm_shuffle_epi8().  Instead we use good old
    shifting and masking.

  - Performance is very similar to SSSE3, close enough I'm having trouble
    telling which is faster.  I think we should let ourselves circle back
    on whether we need an SSSE3 version later.  When possible it's nice
    to stick to SSE2: it's most available, and performs most uniformly
    across different chips.

This makes Sk4x4f fast on Windows and Linux, and may help mobile x86.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1817353005

Review URL: https://codereview.chromium.org/1817353005