[Openmp-commits] [PATCH] D97413: [OpenMP] Fix clang-cl build error regarding TSX intrinsics

Mon Mar 1 04:39:16 PST 2021

hans accepted this revision.
hans added a comment.
This revision is now accepted and ready to land.

In D97413#2588041 <https://reviews.llvm.org/D97413#2588041>, @jlpeyton wrote:

> In D97413#2587137 <https://reviews.llvm.org/D97413#2587137>, @hans wrote:
>
>> Oh, and I just realized: just because my machine supports RTM doesn't necessarily mean we want to use it, since these builds will then be used on all kinds of machines. This might be a bigger problem with the runtime's build config though.
>
> I think only the build compiler needs to support the instructions, not your machine.
> This shouldn't cause a problem since the RTM instrinsics are only used inside a specific lock kind which the user must select using an environment variable.

I see. Thanks for clarifying!

================
Comment at: openmp/runtime/cmake/config-ix.cmake:179
+  if (LIBOMP_HAVE_MRTM_FLAG)
+    set(CMAKE_REQUIRED_FLAGS -mrtm)
+  endif()
----------------
I looked for how CMAKE_REQUIRED_FLAGS is used in other places, and this pattern seems common:

```
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11")
```

Maybe that is safer, in case CMAKE_REQUIRED_FLAGS already holds some flag that is important for the build.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D97413/new/

https://reviews.llvm.org/D97413