[PATCH] [OPENMP] Added option -fopenmp=libiomp5

[Alp Toker]

On 27/02/2014 11:58, Alexey Bataev wrote:
>
> ================
> Comment at: lib/Driver/Tools.cpp:5237-5240
> @@ -5236,4 +5236,6 @@
>   
> -  if (Args.hasArg(options::OPT_fopenmp))
> +  if (Args.hasArg(options::OPT_fopenmp)) {
>       // This is more complicated in gcc...
>       CmdArgs.push_back("-lgomp");
> +  } else if (const Arg *A = Args.getLastArg(options::OPT_fopenmp_EQ)) {
> +    if (StringRef(A->getValue()) == "libiomp5")
> ----------------
> Dmitri Gribenko wrote:
>> What happens if the user passes -fopenmp -fopenmp=libiomp5?
> Then only -fopenmp will work and the warning for -fopenmp=libiomp5 will be emitted. I thought that we have to be conservative with -fopenmp option.
>
> ================
> Comment at: test/OpenMP/parallel_ast_print.cpp:3
> @@ -2,3 +2,3 @@
>   // RUN: %clang_cc1 -fopenmp -x c++ -std=c++11 -emit-pch -o %t %s
> -// RUN: %clang_cc1 -fopenmp -std=c++11 -include-pch %t -fsyntax-only -verify %s -ast-print | FileCheck %s
> +// RUN: %clang_cc1 -fopenmp=libiomp5 -std=c++11 -include-pch %t -fsyntax-only -verify %s -ast-print | FileCheck %s
>   // expected-no-diagnostics
> ----------------
> Dmitri Gribenko wrote:
>> If this flag only changes the linker option, then there is no need to update AST tests with it.
> No, it also turns on OpenMP support in front end. You can consider -fopenmp=libiomp5 option as an extension for -fopenmp option. My idea was not only link libiomp5, but also generate the IR for libiomp5 runtime only if -fopenmp=libiomp5 is specified. If -fopenmp is specified, the IR won't be generated (for compatibility).

I'd expect the IR generated for the two runtimes to be identical given 
that the target is a stable ABI.

How about just passing -lomp from the driver to the linker and leaving 
it up to distributors to symlink the implementation (GNU or Intel) to 
the generic name, the same way -pthread works?

(The -stdlib= optional argument was necessary only due to the need to 
modify header search paths and select the correct ABI between the two 
C++ standard libraries simultaneously. Neither of these needs ought to 
exist with OpenMP runtimes.)

Alp.

>
>
> http://llvm-reviews.chandlerc.com/D2841
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