r245304 - We shouldn't need to pass -fno-strict-aliasing when building clang with clang.

[Hal Finkel via cfe-commits]

----- Original Message -----
> From: "Chris Bieneman via cfe-commits" <cfe-commits at lists.llvm.org>
> To: cfe-commits at lists.llvm.org
> Sent: Tuesday, August 18, 2015 11:15:44 AM
> Subject: r245304 - We shouldn't need to pass -fno-strict-aliasing when building clang with clang.
> 
> Author: cbieneman
> Date: Tue Aug 18 11:15:44 2015
> New Revision: 245304
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=245304&view=rev
> Log:
> We shouldn't need to pass -fno-strict-aliasing when building clang
> with clang.
> 
> Summary: The code comments in the Makefile indicate this was put in
> place to support issues when building clang with GCC. Today clang's
> strict aliasing works, so we shouldn't pass -fno-strict-aliasing
> when building with clang.
> 
> Reviewers: bogner, echristo
> 
> Subscribers: cfe-commits
> 
> Differential Revision: http://reviews.llvm.org/D12036
> 
> Modified:
>     cfe/trunk/CMakeLists.txt
>     cfe/trunk/Makefile
> 
> Modified: cfe/trunk/CMakeLists.txt
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/CMakeLists.txt?rev=245304&r1=245303&r2=245304&view=diff
> ==============================================================================
> --- cfe/trunk/CMakeLists.txt (original)
> +++ cfe/trunk/CMakeLists.txt Tue Aug 18 11:15:44 2015
> @@ -253,7 +253,10 @@ configure_file(
>  
>  # Add appropriate flags for GCC
>  if (LLVM_COMPILER_IS_GCC_COMPATIBLE)
> -  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-common
> -Woverloaded-virtual -fno-strict-aliasing")
> +  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-common
> -Woverloaded-virtual")
> +  if (NOT "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
> +    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-strict-aliasing")
> +  endif ()
>  
>    # Enable -pedantic for Clang even if it's not enabled for LLVM.
>    if (NOT LLVM_ENABLE_PEDANTIC)
> 
> Modified: cfe/trunk/Makefile
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/Makefile?rev=245304&r1=245303&r2=245304&view=diff
> ==============================================================================
> --- cfe/trunk/Makefile (original)
> +++ cfe/trunk/Makefile Tue Aug 18 11:15:44 2015
> @@ -67,8 +67,11 @@ endif
>  #   http://gcc.gnu.org/PR41874
>  #   http://gcc.gnu.org/PR41838
>  #
> -# We can revisit this when LLVM/Clang support it.
> +# We don't need to do this if the host compiler is clang.
> +ifeq ($(CXX_COMPILER), "clang")
>  CXX.Flags += -fno-strict-aliasing
> +endif

This logic is backwards, it disables strict aliasing when the compiler is clang, and leaves it enabled otherwise. Perhaps you want to ifeq -> ifneq?

 -Hal

> +
>  
>  # Set up Clang's tblgen.
>  ifndef CLANG_TBLGEN
> 
> 
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory