[LLVMdev] Turning on/off instruction extensions

[Hal Finkel]

On Mon, 2011-11-28 at 17:49 +0100, Pablo Barrio wrote:
> How can I install the patch? Any step-by-step guide?

First, grab the trunk versions of llvm and clang. This is detailed on
http://clang.llvm.org/get_started.html

Then you apply the patch. On a Unix-like system, this is something like:
cd llvm
patch -p1 < /path/to/the-patch-file.diff

Then you rebuild.

If you have any further questions, or need a more-detailed answer,
please let me know.

 -Hal

> 
> 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
> >> 
> >> _______________________________________________
> >> LLVM Developers mailing list
> >> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> > 
> > -- 
> > Hal Finkel
> > Postdoctoral Appointee
> > Leadership Computing Facility
> > Argonne National Laboratory
> > 
> 

-- 
Hal Finkel
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory