[llvm-commits] [patch] implement cmake LLVM_MULTITHREADED gcc atomic builtin checks.

[Chris Lattner]

On Jul 17, 2009, at 1:55 AM, Xerxes Rånby wrote:

> cmake builds where missing checks for the GCC atomic builtins and thus
> could not define LLVM_MULTITHREADED.
> This in turn made llvm_start_multithreaded() fail when using cmake.
>
> Ok to commit?

Seems reasonable to me, but I'm not a cmake expert :).  Go for it, if  
it causes problems we can back it out.  Thanks!

-Chris

>
> Cheers
> Xerxes
> Index: llvm/include/llvm/Config/config.h.cmake
> ===================================================================
> --- llvm.orig/include/llvm/Config/config.h.cmake	2009-07-15  
> 10:57:56.000000000 +0200
> +++ llvm/include/llvm/Config/config.h.cmake	2009-07-17  
> 10:15:27.000000000 +0200
> @@ -467,6 +467,9 @@
> /* Installation directory for man pages */
> #undef LLVM_MANDIR
>
> +/* Build multithreading support into LLVM */
> +#cmakedefine LLVM_MULTITHREADED ${LLVM_MULTITHREADED}
> +
> /* Define if this is Unixish platform */
> #cmakedefine LLVM_ON_UNIX ${LLVM_ON_UNIX}
>
> Index: llvm/cmake/config-ix.cmake
> ===================================================================
> --- llvm.orig/cmake/config-ix.cmake	2009-07-02 09:43:43.000000000  
> +0200
> +++ llvm/cmake/config-ix.cmake	2009-07-17 10:47:26.000000000 +0200
> @@ -76,6 +76,9 @@
>   add_llvm_definitions( -D_GNU_SOURCE )
> endif()
>
> +# Define LLVM_MULTITHREADED if gcc atomic builtins exists.
> +include(CheckAtomic)
> +
> include(CheckCXXCompilerFlag)
> check_cxx_compiler_flag("-fPIC" SUPPORTS_FPIC_FLAG)
>
> Index: llvm/cmake/modules/CheckAtomic.cmake
> ===================================================================
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ llvm/cmake/modules/CheckAtomic.cmake	2009-07-17  
> 10:40:28.000000000 +0200
> @@ -0,0 +1,18 @@
> +# atomic builtins are required for threading support.
> +
> +INCLUDE(CheckCXXSourceCompiles)
> +	
> +CHECK_CXX_SOURCE_COMPILES("
> +int main() {
> +        volatile unsigned long val = 1;
> +        __sync_synchronize();
> +        __sync_val_compare_and_swap(&val, 1, 0);
> +        __sync_add_and_fetch(&val, 1);
> +        __sync_sub_and_fetch(&val, 1);
> +        return 0;
> +      }
> +" LLVM_MULTITHREADED)
> +
> +if( NOT LLVM_MULTITHREADED )
> +  message(STATUS "Warning: LLVM will be built thread-unsafe because  
> atomic builtins are missing")
> +endif()
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