[Llvm-bgq-discuss] Interpreting CLANG assembly

[Hal Finkel]

----- Original Message -----
> From: "Ian Karlin" <karlin1 at llnl.gov>
> To: llvm-bgq-discuss at lists.alcf.anl.gov
> Sent: Wednesday, April 17, 2013 8:12:23 PM
> Subject: [Llvm-bgq-discuss] Interpreting CLANG assembly
> 
> 
> 
> Hi,
> 
> 
> I'm trying to figure out if CLANG is capable of issuing SIMD
> instructions when xlc is not. I'm having two issues. The first is
> all the debug information is not put inline with the assembly. At a
> minimum it would be nice to know what function or loop(s) I was
> looking at. Second I see you're using a different assembly language
> than xlc. Is there a guide for interpreting it?

Can you be more specific about at what you're looking? The underlying assembly language is indeed the same (and, as far as I know, both compilers use the same underlying system assembler).

The lack of good feedback on loop vectorization is indeed an issue, if you can provide me with access to your source files, I can help you out. Also, if you run clang with the flags: -mllvm -debug-only=loop-vectorize then you'll see output on the loop vectorizer (which is not the only one in there, but this will give you a good start).

To Jeff's comment, there is little reason to use inline assembly with bgclang for SIMD, bgclang supports the same QPX intrinsics as xlc (vec_add, etc.). Use those instead.

 -Hal

> 
> 
> Thanks!
> 
> 
> Ian
> 
> 
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