[Parallel_libs-commits] [PATCH] D24474: [SE] Stop using llvm-config --cxxflags

[Jason Henline via Parallel_libs-commits]

jhen created this revision.
jhen added a reviewer: jlebar.
jhen added subscribers: parallel_libs-commits, jprice.
Herald added subscribers: mgorny, beanz.

Build configuration was adding $(llvm-config --cxxflags) to the
StreamExecutor CXXFLAGS, but this was causing "-O3" to be passed even
for debug builds, and was making debugging difficult.

The llvm-config call was originally introduced to handle the -fno-rtti
flag because an RTTI StreamExecutor could not link with a no-RTTI LLVM.
This patch converts to using the `--has-rtti` flag to `llvm-config` and
only adding the `-fno-rtti` flag if needed, not all the rest of the LLVM
CXXFLAGS.

I have tested this with clang-4.0 and gcc-4.8 on Ubuntu. Some work will
probably have to be done to support MSVC.

https://reviews.llvm.org/D24474

Files:
  streamexecutor/CMakeLists.txt

Index: streamexecutor/CMakeLists.txt
===================================================================
--- streamexecutor/CMakeLists.txt
+++ streamexecutor/CMakeLists.txt
@@ -26,17 +26,17 @@
     include_directories(${LLVM_INCLUDE_DIRS})
     add_definitions(${LLVM_DEFINITIONS})
 
-    # Get the LLVM cxxflags by using llvm-config.
-    #
-    # This is necessary to get -fno-rtti if LLVM is compiled that way.
+    # If LLVM does not have RTTI, don't use it here either.
     execute_process(
         COMMAND
         "${LLVM_BINARY_DIR}/bin/llvm-config"
-        --cxxflags
+        --has-rtti
         OUTPUT_VARIABLE
-        LLVM_CXXFLAGS
+        STREAM_EXECUTOR_LLVM_HAS_RTTI
         OUTPUT_STRIP_TRAILING_WHITESPACE)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${LLVM_CXXFLAGS}")
+    if (NOT STREAM_EXECUTOR_LLVM_HAS_RTTI)
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-rtti")
+    endif()
 
     set(LLVM_CMAKE_PATH "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
     list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_PATH}")


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