impl q14x2 ops in interpreter
These tests cover all the new Q14x2 ops.
As usual, left myself a few TODOs...
While working on this, I uncovered a little subtly about the blend
instructions we use to implement Op::select... unlike the platonic
(cond & true_val) | (~cond & false_val)
the hardware istructions are not bitwise! Each of the fancy blend
instructions like vblendvps or vpblendvb has a fundamental granularity
larger than a bit (4 bytes for vblendvps, 1 byte for vpblendvb). If
you're using a mask with a granularity of say, 2 bytes, you need to be
using something with equally fine granularity --- bitwise is ok,
bytewise is ok, 2-byte-wise is ok, but 4-byte-wise isn't.
Took a quick survey, and the Op::select we're using for x86 and ARM
JITs are both bytewise, so I think they're fine. Would have to think
a bit about LLVM, but these unit tests should at least fire if it were
wrong. The skvx if_then_else() I've been using in the interpreter has
been 4-byte-wise, but I'm refining that down to 1-byte-wise with
Reviewed-by: Herb Derby <firstname.lastname@example.org>
Commit-Queue: Mike Klein <email@example.com>
3 files changed