HLSL doesn't support access specifiers. This change has two components:
1) Make default access for classes public
2) Diagnose the use of access specifiers as a clang HLSL extension
As long as the default behavior for access specifiers matches HLSL,
allowing them to be used doesn't cause sourece incompatability with
valid code. As such enabling them as a clang extension seems like a
reasonable approach.
Fixes#55124
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D124487
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
Chris Bieneman