Implementation of
[SPV_KHR_float_controls2](https://github.khronos.org/SPIRV-Registry/extensions/KHR/SPV_KHR_float_controls2.html)
extension, and corresponding tests.
Some of the tests make use of `!spirv.ExecutionMode` LLVM named
metadata. This is because some SPIR-V instructions don't have a direct
equivalent in LLVM IR, so the SPIR-V Target uses different LLVM named
metadata to convey the necessary information. Below, you will find an
example from one of the newly added tests:
```
!spirv.ExecutionMode = !{!19, !20, !21, !22, !23, !24, !25, !26, !27}
!19 = !{ptr @k_float_controls_float, i32 6028, float poison, i32 131079}
!20 = !{ptr @k_float_controls_all, i32 6028, float poison, i32 131079}
!21 = !{ptr @k_float_controls_float, i32 31}
!22 = !{ptr @k_float_controls_all, i32 31}
!23 = !{ptr @k_float_controls_float, i32 4461, i32 32}
!24 = !{ptr @k_float_controls_all, i32 4461, i32 16}
!25 = !{ptr @k_float_controls_all, i32 4461, i32 32}
!26 = !{ptr @k_float_controls_all, i32 4461, i32 64}
!27 = !{ptr @k_float_controls_all, i32 4461, i32 128}
```
`!spirv.ExecutionMode` contains a list of metadata nodes, and each of
them specifies the required operands for expressing a particular
`OpExecutionMode` instruction in SPIR-V. For example, `!19 = !{ptr
@k_float_controls_float, i32 6028, float poison, i32 131079}` will be
lowered to `OpExecutionMode [[k_float_controls_float_ID]]
FPFastMathDefault [[float_type_ID]] 131079`.
---------
Co-authored-by: Dmitry Sidorov <dmitry.sidorov@intel.com>
Add handling for FPFastMathMode in SPIR-V shaders. This is a first pass
that
simply does a direct translation when the proper extension is available.
This will unblock work for HLSL. However, it is not a full solution.
The default math mode for spir-v is determined by the API. When
targeting Vulkan many of the fast math options are assumed. We should do
something particular when targeting Vulkan.
We will also need to handle the hlsl "precise" keyword correctly when
FPFastMathMode is not available.
Unblockes https://github.com/llvm/llvm-project/issues/140739, but we are
keeing it open to track the remaining issues mentioned above.
