The previous implementation was fine for GLSL which doesn't really have
a signed modulus/remainder. They just leave the behavior undefined
whenever either source is negative. However, in SPIR-V, there is a
defined behavior for negative arguments. This commit beefs up the pass
so that it handles both correctly. Tested using a hacked up version of
the Vulkan CTS test to get 64-bit support.
Reviewed-by: Matt Turner <mattst88@gmail.com>
The algorithms used by this pass, especially for division, are heavily
based on the work Ian Romanick did for the similar int64 lowering pass
in the GLSL compiler.
v2: Properly handle vectors
v3: Get rid of log2_denom stuff. Since we're using bcsel, we do all the
calculations anyway and this is just extra instructions.
v4:
- Add back in the log2_denom stuff since it's needed for ensuring that
the shifts don't overflow.
- Rework the looping part of the pass to be easier to expand.
Reviewed-by: Matt Turner <mattst88@gmail.com>
Jason Ekstrand