[llvm-branch-commits] [llvm] 28f6aac - [CMake] Fix LLVM build non-determinism on RHEL

[Tom Stellard via llvm-branch-commits]

Author: Amy Kwan
Date: 2019-11-27T11:17:05-08:00
New Revision: 28f6aac1c102f7d8ba8afce900079e42e67bedca

URL: https://github.com/llvm/llvm-project/commit/28f6aac1c102f7d8ba8afce900079e42e67bedca
DIFF: https://github.com/llvm/llvm-project/commit/28f6aac1c102f7d8ba8afce900079e42e67bedca.diff

LOG: [CMake] Fix LLVM build non-determinism on RHEL

On RHEL, the OS tooling (ar, ranlib) is not deterministic by default.
Therefore, we cannot get bit-for-bit identical builds.

The goal of this patch is that it adds the flags required to force determinism.

Differential Revision: https://reviews.llvm.org/D64817

(cherry picked from commit c84c62c50aa8524dbf96217c337f3b5ee4139000)

Added: 
    

Modified: 
    llvm/cmake/modules/HandleLLVMOptions.cmake

Removed: 
    


################################################################################
diff  --git a/llvm/cmake/modules/HandleLLVMOptions.cmake b/llvm/cmake/modules/HandleLLVMOptions.cmake
index 59e1bdb8ebc4..4425eb91a5fc 100644
--- a/llvm/cmake/modules/HandleLLVMOptions.cmake
+++ b/llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -145,6 +145,28 @@ if(APPLE)
   set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} -Wl,-flat_namespace -Wl,-undefined -Wl,suppress")
 endif()
 
+if(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
+  # RHEL7 has ar and ranlib being non-deterministic by default. The D flag forces determinism,
+  # however only GNU version of ar and ranlib (2.27) have this option. 
+  # RHEL DTS7 is also affected by this, which uses GNU binutils 2.28
+  execute_process(COMMAND ${CMAKE_AR} rD t.a
+                  WORKING_DIRECTORY ${CMAKE_BINARY_DIR} RESULT_VARIABLE AR_RESULT OUTPUT_VARIABLE RANLIB_OUTPUT)
+  if(${AR_RESULT} EQUAL 0)
+    execute_process(COMMAND ${CMAKE_RANLIB} -D t.a
+                    WORKING_DIRECTORY ${CMAKE_BINARY_DIR} RESULT_VARIABLE RANLIB_RESULT OUTPUT_VARIABLE RANLIB_OUTPUT)
+    if(${RANLIB_RESULT} EQUAL 0)
+      set(CMAKE_C_ARCHIVE_CREATE "<CMAKE_AR> Dqc <TARGET> <LINK_FLAGS> <OBJECTS>")
+      set(CMAKE_C_ARCHIVE_APPEND "<CMAKE_AR> Dq  <TARGET> <LINK_FLAGS> <OBJECTS>")
+      set(CMAKE_C_ARCHIVE_FINISH "<CMAKE_RANLIB> -D <TARGET>")
+
+      set(CMAKE_CXX_ARCHIVE_CREATE "<CMAKE_AR> Dqc <TARGET> <LINK_FLAGS> <OBJECTS>")
+      set(CMAKE_CXX_ARCHIVE_APPEND "<CMAKE_AR> Dq  <TARGET> <LINK_FLAGS> <OBJECTS>")
+      set(CMAKE_CXX_ARCHIVE_FINISH "<CMAKE_RANLIB> -D <TARGET>")
+    endif()
+    file(REMOVE ${CMAKE_BINARY_DIR}/t.a)
+  endif()
+endif()
+
 if(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
   if(NOT LLVM_BUILD_32_BITS)
     if (CMAKE_CXX_COMPILER_ID MATCHES "XL")