[LLVMdev] LLVM Loop Vectorizer puzzle

Nadav Rotem nrotem at apple.com
Thu May 23 09:02:10 PDT 2013

On May 23, 2013, at 8:52 AM, "Redmond, Paul" <paul.redmond at intel.com> wrote:

> !0 = metadata !{ metadata !1, metadata !2 }
> !1 = metadata !{ metadata !"llvm.loop.parallel" }
> !2 = metadata !{ metadata !"llvm.vectorization.vector_width", i32 8 }
> I'm not even sure you would need the llvm.loop.parallel anymore since the vectorizer could just look to see if the loop id on a parallel_loop_access matches the loop id of the loop being vectorized. 
> Does this make any sense?

Yes. It makes sense to me. 

>> If we decide, that
>> #pragma ivdep
>> should imply forced vectorization (which I am not sure it should), the front-end can than in addition to the llvm.loop.parallel metadata, emit meta data to force vectorization. But, I don’t think we should overload the semantics of llvm.loop.parallel.
> ivdep doesn't force vectorization. It just says if you can't prove there is or isn't a dependency the assume there isn't.

I think that we should come up with a better name.  I am okay with providing ICC aliases, but I think that we should come up with slightly less cryptic names for clang. 
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