This patch:
- Adds SPIR-V backend's registered generator magic number to the emitted
binary. The magic number consists of the generator ID (43) and LLVM
major version.
- Adds SPIR-V version to the binary.
- Allows reading the expected (maximum supported) SPIR-V version from
the target triple.
- Uses VersionTuple for representing versions throughout the backend's
codebase.
- Registers v1.6 for spirv32 and spirv64 triple.
See more: https://github.com/KhronosGroup/SPIRV-Headers/commit/7d500c
This PR is to add explicit support for SPV_KHR_float_controls
(https://github.com/KhronosGroup/SPIRV-Registry/blob/main/extensions/KHR/SPV_KHR_float_controls.asciidoc).
This extension is included into SPIR-V after version 1.4, but in case of
lower versions it is to be included explicitly and OpExtension must be
present in the module with `OpExtension "SPV_KHR_float_controls"`.
This PR fixes this issue and fixes the test case
test/CodeGen/SPIRV/exec_mode_float_control_khr.ll to account for a
version lower than 1.4.
