[LLVMdev] libiomp, not libgomp as default library linked with -fopenmp

C Bergström
2015-04-30T22:26:31Z

I'm trimming everything - sorry too hard to manage the thread in my
current email client
--
1) I'd rather see a configure time option to change the name rather
than just switching it. It's not user facing and who really cares what
the name is. (I don't) It's one more change for others who have
established naming (Intel) to have to carry a patch. (I'd like to play
nice here.. UH, PathScale, foobar may also want to use a different
name.. etc)

2) Benchmarks - There's SPEC OMP2012, but I'm not sure if a gcc vs
llvm comparison is really going to stress the runtime sufficiently
enough to play the blame game. The retired OMP benchmark may use a
limited enough subset of features to work with llvm+gomp||iomp.. (That
way you could do a 1:1 comparison) - If that does work I'm not yet
confident it would expose any real performance issues in the runtime.
(You'd need to test it on a system with *A LOT* of cores)

There are lowering differences between the internal API as well..

Ancedotal evidence - Intel's runtime (essentially the same code as
"llvm omp") is used by Intel for OMP SPEC submissions as compared to
nobody publishing record setting performance with gomp...