Speculate that we can modify the SSA value in-place. As long as it is
not used after the modify, this is fine.
Also need to make sure we don't attempt to RMW something that is
impossible to modify.
Emit synthetic functions before function constants.
Support use of spvQuantizeToF16() in function constants for numerical
behavior consistency with the op code.
Ensure subnormal results from OpQuantizeToF16 are flushed to zero per SPIR-V spec.
Adjust SPIRV-Cross unit test reference shaders to accommodate these changes.
Any MSL reference shader that inclues a synthetic function is affected,
since the location it is emitted has changed.
Based on CTS testing, math optimizations between MSL and Vulkan are inconsistent.
In some cases, enabling MSL's fast-math compilation option matches Vulkan's math
results. In other cases, disabling it does. Broadly enabling or disabling fast-math
across all shaders results in some CTS test failures either way.
To fix this, selectively enable/disable fast-math optimizations in the MSL code,
using metal::fast and metal::precise function namespaces, where supported, and
the [[clang::optnone]] function attribute otherwise.
Adjust SPIRV-Cross unit test reference shaders to accommodate these changes.
This avoids a lot of huge code changes.
Arrays generally cannot be copied in and out of buffers, at least no
compiler frontend seems to do it.
Also avoids a lot of issues surrounding packed vectors and matrices.
