Optimize lowering of x86 byte and word vector unpack.

BUG=swiftshader:15

Change-Id: Id0d3bed46d00336fc31501c41a26ebe2d4ddd697
Reviewed-on: https://chromium-review.googlesource.com/392626
Reviewed-by: Jim Stichnoth <stichnot@chromium.org>
Tested-by: Nicolas Capens <nicolascapens@google.com>
6 files changed