Fix the calling convention used for the call in the entry point
wrapper. No calling convention is currently set. It can easily use the
calling convention of the function that is being called.
Without this, there is a mismatch in the calling convention between the
call site and the callee. This is undefined behaviour.
Add SPIR-V backend support for the HLSL SV_DispatchThreadID semantic
attribute, which is lowered to a @llvm.dx.thread.id intrinsic in LLVM
IR. In the SPIR-V backend, this is now correctly translated to a
`GlobalInvocationId` builtin variable.
Fixes#82534
Support SV_DispatchThreadID attribute.
Translate it into dx.thread.id in clang codeGen.
Reviewed By: beanz, aaron.ballman
Differential Revision: https://reviews.llvm.org/D133983
