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
HLSL entry function parameters must have parameter annotations. This
allows appropriate intrinsic values to be populated into parameters
during code generation.
This does not handle entry function return values, which will be
handled in a subsequent commit because we don't currently support any
annotations that are valid for function returns.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D131625
HLSL has a language feature called Semantics which get attached to
declarations like attributes and are used in a variety of ways.
One example of semantic use is here with the `SV_GroupIndex` semantic
which, when applied to an input for a compute shader is pre-populated
by the driver with a flattened thread index.
Differential Revision: https://reviews.llvm.org/D122699
# Conflicts:
# clang/include/clang/Basic/Attr.td
# clang/include/clang/Basic/AttrDocs.td
Xiang Li