[llvm] 84f80b1 - [CMake] Only detect the linker once in AddLLVM.cmake

[Louis Dionne via llvm-commits]

Author: Louis Dionne
Date: 2020-02-19T13:53:38-05:00
New Revision: 84f80b1faaeb385a178f4b517d92d29ca6a6d854

URL: https://github.com/llvm/llvm-project/commit/84f80b1faaeb385a178f4b517d92d29ca6a6d854
DIFF: https://github.com/llvm/llvm-project/commit/84f80b1faaeb385a178f4b517d92d29ca6a6d854.diff

LOG: [CMake] Only detect the linker once in AddLLVM.cmake

Summary:
Otherwise, the build output contains a bunch of "Linker detection: <xxx>"
lines that are really redundant. We also make redundant calls to the
linker, although that is a smaller concern.

Reviewers: smeenai

Subscribers: mgorny, fedor.sergeev, jkorous, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68648

Added: 
    

Modified: 
    llvm/cmake/modules/AddLLVM.cmake

Removed: 
    


################################################################################
diff  --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
index 71ed1b8a3af1..408423ba1887 100644
--- a/llvm/cmake/modules/AddLLVM.cmake
+++ b/llvm/cmake/modules/AddLLVM.cmake
@@ -162,49 +162,54 @@ function(add_llvm_symbol_exports target_name export_file)
   set(LLVM_COMMON_DEPENDS ${LLVM_COMMON_DEPENDS} PARENT_SCOPE)
 endfunction(add_llvm_symbol_exports)
 
-if(APPLE)
-  execute_process(
-    COMMAND "${CMAKE_LINKER}" -v
-    ERROR_VARIABLE stderr
-    )
-  set(LLVM_LINKER_DETECTED YES)
-  if("${stderr}" MATCHES "PROJECT:ld64")
-    set(LLVM_LINKER_IS_LD64 YES)
-    message(STATUS "Linker detection: ld64")
-  else()
-    set(LLVM_LINKER_DETECTED NO)
-    message(STATUS "Linker detection: unknown")
-  endif()
-elseif(NOT WIN32)
-  # Detect what linker we have here
-  if( LLVM_USE_LINKER )
-    set(command ${CMAKE_C_COMPILER} -fuse-ld=${LLVM_USE_LINKER} -Wl,--version)
-  else()
-    separate_arguments(flags UNIX_COMMAND "${CMAKE_EXE_LINKER_FLAGS}")
-    set(command ${CMAKE_C_COMPILER} ${flags} -Wl,--version)
-  endif()
-  execute_process(
-    COMMAND ${command}
-    OUTPUT_VARIABLE stdout
-    ERROR_VARIABLE stderr
-    )
-  set(LLVM_LINKER_DETECTED YES)
-  if("${stdout}" MATCHES "GNU gold")
-    set(LLVM_LINKER_IS_GOLD YES)
-    message(STATUS "Linker detection: GNU Gold")
-  elseif("${stdout}" MATCHES "^LLD")
-    set(LLVM_LINKER_IS_LLD YES)
-    message(STATUS "Linker detection: LLD")
-  elseif("${stdout}" MATCHES "GNU ld")
-    set(LLVM_LINKER_IS_GNULD YES)
-    message(STATUS "Linker detection: GNU ld")
-  elseif("${stderr}" MATCHES "Solaris Link Editors" OR
-         "${stdout}" MATCHES "Solaris Link Editors")
-    set(LLVM_LINKER_IS_SOLARISLD YES)
-    message(STATUS "Linker detection: Solaris ld")
-  else()
-    set(LLVM_LINKER_DETECTED NO)
-    message(STATUS "Linker detection: unknown")
+if (NOT DEFINED LLVM_LINKER_DETECTED)
+  if(APPLE)
+    execute_process(
+      COMMAND "${CMAKE_LINKER}" -v
+      ERROR_VARIABLE stderr
+      )
+    if("${stderr}" MATCHES "PROJECT:ld64")
+      set(LLVM_LINKER_DETECTED YES CACHE INTERNAL "")
+      set(LLVM_LINKER_IS_LD64 YES CACHE INTERNAL "")
+      message(STATUS "Linker detection: ld64")
+    else()
+      set(LLVM_LINKER_DETECTED NO CACHE INTERNAL "")
+      message(STATUS "Linker detection: unknown")
+    endif()
+  elseif(NOT WIN32)
+    # Detect what linker we have here
+    if( LLVM_USE_LINKER )
+      set(command ${CMAKE_C_COMPILER} -fuse-ld=${LLVM_USE_LINKER} -Wl,--version)
+    else()
+      separate_arguments(flags UNIX_COMMAND "${CMAKE_EXE_LINKER_FLAGS}")
+      set(command ${CMAKE_C_COMPILER} ${flags} -Wl,--version)
+    endif()
+    execute_process(
+      COMMAND ${command}
+      OUTPUT_VARIABLE stdout
+      ERROR_VARIABLE stderr
+      )
+    if("${stdout}" MATCHES "GNU gold")
+      set(LLVM_LINKER_DETECTED YES CACHE INTERNAL "")
+      set(LLVM_LINKER_IS_GOLD YES CACHE INTERNAL "")
+      message(STATUS "Linker detection: GNU Gold")
+    elseif("${stdout}" MATCHES "^LLD")
+      set(LLVM_LINKER_DETECTED YES CACHE INTERNAL "")
+      set(LLVM_LINKER_IS_LLD YES CACHE INTERNAL "")
+      message(STATUS "Linker detection: LLD")
+    elseif("${stdout}" MATCHES "GNU ld")
+      set(LLVM_LINKER_DETECTED YES CACHE INTERNAL "")
+      set(LLVM_LINKER_IS_GNULD YES CACHE INTERNAL "")
+      message(STATUS "Linker detection: GNU ld")
+    elseif("${stderr}" MATCHES "Solaris Link Editors" OR
+           "${stdout}" MATCHES "Solaris Link Editors")
+      set(LLVM_LINKER_DETECTED YES CACHE INTERNAL "")
+      set(LLVM_LINKER_IS_SOLARISLD YES CACHE INTERNAL "")
+      message(STATUS "Linker detection: Solaris ld")
+    else()
+      set(LLVM_LINKER_DETECTED NO CACHE INTERNAL "")
+      message(STATUS "Linker detection: unknown")
+    endif()
   endif()
 endif()