[PATCH] D134206: Fix -fuse-ld to be linker flag in feature detection check

[Kevin Gleason via Phabricator via llvm-commits]

GleasonK created this revision.
GleasonK added a reviewer: mehdi_amini.
Herald added subscribers: bzcheeseman, kosarev, rriddle, pengfei, tpr.
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GleasonK requested review of this revision.
Herald added subscribers: llvm-commits, stephenneuendorffer.
Herald added a project: LLVM.

Discovered an issue working in StableHLO when attempting to build with `-Wall -Werror`:
https://github.com/openxla/stablehlo/pull/137

Currently, if `LLVM_USE_LLD` and `-DCMAKE_CXX_FLAGS="${CMAKE_CXX_FLAGS} -Wall -Werror"`
are both specified for build, the build will error with:

  -- Performing Test CXX_SUPPORTS_CUSTOM_LINKER - Failed
  CMake Error at /usr/local/google/home/gleasonk/Coding/llvm-build/lib/cmake/llvm/HandleLLVMOptions.cmake:309 (message):
    Host compiler does not support '-fuse-ld=lld'
  ...
  
  $ cat <build_dir>/CMakeFiles/CMakeError.log
  ...
  clang: error: argument unused during compilation: '-fuse-ld=lld' [-Werror,-Wunused-command-line-argument]

It looks like other repos have hit this same issue:

- https://github.com/golang/go/issues/41527 (mentioned in comment)
- https://github.com/iree-org/iree/pull/7450

This can be reproduced in llvm-project with the following build command:

  # Compile command taken from https://mlir.llvm.org/getting_started/
  # and modified for use case
  cmake -G Ninja ../llvm \
     -DLLVM_ENABLE_PROJECTS=mlir \
     -DLLVM_BUILD_EXAMPLES=ON \
     -DLLVM_TARGETS_TO_BUILD="X86;NVPTX;AMDGPU" \
     -DCMAKE_BUILD_TYPE=Release \
     -DLLVM_ENABLE_ASSERTIONS=ON \
     -DCMAKE_CXX_COMPILER=clang++ \
     -DCMAKE_C_COMPILER=clang \
     -DLLVM_ENABLE_LLD=ON \
     -DCMAKE_CXX_FLAGS="${CMAKE_CXX_FLAGS} -Wall -Werror"


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D134206

Files:
  llvm/cmake/modules/HandleLLVMOptions.cmake


Index: llvm/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -302,15 +302,12 @@
 endif()
 
 if( LLVM_USE_LINKER )
-  set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
-  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fuse-ld=${LLVM_USE_LINKER}")
+  append("-fuse-ld=${LLVM_USE_LINKER}"
+    CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
   check_cxx_source_compiles("int main() { return 0; }" CXX_SUPPORTS_CUSTOM_LINKER)
   if ( NOT CXX_SUPPORTS_CUSTOM_LINKER )
     message(FATAL_ERROR "Host compiler does not support '-fuse-ld=${LLVM_USE_LINKER}'")
   endif()
-  set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
-  append("-fuse-ld=${LLVM_USE_LINKER}"
-    CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
 endif()
 
 if( LLVM_ENABLE_PIC )


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