[LLVMdev] Turning on/off instruction extensions

[Pablo Barrio]

How can I install the patch? Any step-by-step guide?

Thanks,
Pablo

On 24/11/2011, at 15:33, Hal Finkel wrote:

> On Thu, 2011-11-24 at 15:09 +0100, Pablo Barrio López-Cortijo wrote:
>> Hi everybody,
>> 
>> I'm trying to run some examples with different backend options (turning
>> on/off SSE, 3dnow, or MMX instructions). However, I don't see any
>> difference in terms of execution time. Does anybody know which language
>> constructs (in C/C++ preferably) should I try to make these instructions
>> generated (and thus make a difference between a backend that enables
>> them or not) ?
>> 
>> I tried generating vector instructions with loops but it's not
>> happening. Perhaps Polly can generate vector instructions?
> 
> You can also try my basic-block autovectorization patch.
> 
> http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20111121/132206.html
> 
> After applying the patch (I recommend applying it to the current trunk),
> then run clang with the flags:
> -mllvm -vectorize -mllvm -unroll-allow-partial
> (the -unroll-allow-partial is not necessary for the vectorization, but
> tends to expose additional vectorization opportunities). The basic-block
> vectorizer has a number of flags that can be used to customize its
> behavior, so if it is not vectorizing something that you think it should
> be (or is doing something performance detrimental), please let me know
> and I'll be happy to help.
> 
> -Hal
> 
>> 
>> Thanks ahead,
>> 
>> Pablo
>> DIE-UPM
>> Madrid
>> 
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> 
> -- 
> Hal Finkel
> Postdoctoral Appointee
> Leadership Computing Facility
> Argonne National Laboratory
>