[llvm] [SPIR-V] Fix SPIRVEmitIntrinsics undefined behavior (PR #123625)

[Michal Paszkowski via llvm-commits]

michalpaszkowski wrote:

This PR fixes the undefined behavior issues discovered by buildbots after adding SPIRV to LLVM_ALL_TARGETS in https://github.com/llvm/llvm-project/pull/119653

https://github.com/llvm/llvm-project/pull/123625