Expand _01 half<->float limitation to _finite.  Simplify.

    It's become clear we need to sometimes deal with values <0 or >1.
    I'm not yet convinced we care about NaN or +-inf.

    We had some fairly clever tricks and optimizations here for NEON
    and SSE.  I've thrown them out in favor of a single implementation.
    If we find the specializations mattered, we can certainly figure out
    how to extend them to this new range/domain.

    This happens to add a vectorized float -> half for ARMv7, which was
    missing from the _01 version.  (The SSE strategy was not portable to
    platforms that flush denorm floats to zero.)

    I've tested the full float range for FloatToHalf on my desktop and a 5x.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2145663003
CQ_INCLUDE_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot;master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot,Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-Fast-Trybot

Committed: https://skia.googlesource.com/skia/+/3296bee70d074bb8094b3229dbe12fa016657e90
Review-Url: https://codereview.chromium.org/2145663003
11 files changed