[all-commits] [llvm/llvm-project] a60b8f: [OpenCL] Allow undefining header-only features

[Sven van Haastregt via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a60b8f468119065f8a6cb4a16598263cb00de0b5
      https://github.com/llvm/llvm-project/commit/a60b8f468119065f8a6cb4a16598263cb00de0b5
  Author: Sven van Haastregt <sven.vanhaastregt at arm.com>
  Date:   2023-01-16 (Mon, 16 Jan 2023)

  Changed paths:
    M clang/lib/Headers/opencl-c-base.h
    M clang/test/SemaOpenCL/features.cl

  Log Message:
  -----------
  [OpenCL] Allow undefining header-only features

`opencl-c-base.h` always defines 5 particular feature macros for
SPIR-V, making it impossible to disable those features.

To allow disabling any of those features, let the header recognize
`__undef_<feature>` macros.  The user can then pass the
`-D__undef_<feature>` flag on the command line to disable a specific
feature.  The __undef macro could potentially also be set from
`-cl-ext=-feature`, but for now only change the header and only
provide __undef macros for the 5 features that are always enabled in
`opencl-c-base.h`.

Differential Revision: https://reviews.llvm.org/D141297