[HLSL] vector subscript indexing

[llvm-beanz]

HLSL vectors allow subscript indexing for individual elements.

Acceptance Criteria

• Specify the expected behavior for out-of-range subscript access
• Implementation and tests for vector subscript access

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Chris B (llvm-beanz)

HLSL vectors allow subscript indexing for individual elements.

Acceptance Criteria

• Specify the expected behavior for out-of-range subscript access
• Implementation and tests for vector subscript access