The existing code didn't work properly with half types since the $mat
type encompassed both halfNxM and floatNxM. This was fixed by splitting
the half types out of $mat into a separate $matH generic.
Unit tests now compile properly for GLSL, but generate errors in SPIR-V
and generate Metal code which attempts to call a non-existent intrinsic.
Change-Id: I2fff10f0dd7f00534bf6b1d5b13354543694194e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/342926
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
