[Llvm-bgq-discuss] Interpreting CLANG assembly

[Karlin, Ian]

Hi Hal,

I'm not using intrinsics I was more trying to figure out what was being
made SIMD by the compiler and what instructions.  The hint to the assym
language was most of what I needed.  I'll try out your flags and if that
gets me the rest I'll be good.  If not I'll send you the code.

On a side note is there a way to turn off SIMD generation only?  That is
another experiment I"m planning on trying.

Thanks!

Ian

On 4/17/13 9:06 PM, "Hal Finkel" <hfinkel at anl.gov> wrote:

>----- 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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