improve ARMv7 8-bit codegen

We need to make two changes to keep all values in registers:

    1) pass raw U8 values instead of V structs that wrap them
    2) switch to aapcs-vfp, which allows exactly 8x U8 arguments

Code generation goes from ridiculous looking to lovely.

Change-Id: Ibd53bdd86345b59bd987a1f79205645d80c5cbc3
Reviewed-on: https://skia-review.googlesource.com/40021
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
1 file changed