[LLVMdev] Vectorization: Next Steps

[Duncan Sands]

Hi Jack,

On 03/02/12 14:45, Jack Howarth wrote:
> On Fri, Feb 03, 2012 at 09:49:30AM +0100, Duncan Sands wrote:
>> Hi Hal,
>>
>>> As some of you may know, I committed my basic-block autovectorization
>>> pass a few days ago. I encourage anyone interested to try it out (pass
>>> -vectorize to opt or -mllvm -vectorize to clang) and provide feedback.
>>> Especially in combination with -unroll-allow-partial, I have observed
>>> some significant benchmark speedups, but, I have also observed some
>>> significant slowdowns.
>>
>> codegen for vector constructs is not always that great in my experience.
>> It could be that your vectorizer is doing the right thing, and it's
>> codegen that needs to be improved.  For example when I use the GCC
>> autovectorizer I often see LLVM codegen unnecessarily scalarizing the
>> vector code.  Did you try to analyse these slowdowns?
>>
>> Ciao, Duncan.
>
> Duncan,
>    Is there a recommended approach for testing the new -vectorize support
> within dragonegg?

as of a few minutes ago you can turn it on using
   -fplugin-arg-dragonegg-llvm-option=-vectorize

Ciao, Duncan.