[LLVMdev] RFC - Profile Guided Optimization in LLVM

Evan Cheng evan.cheng at apple.com
Mon Jun 17 17:48:10 PDT 2013


On Jun 17, 2013, at 6:54 AM, Diego Novillo <dnovillo at google.com> wrote:

> On 2013-06-15 14:18 , Evan Cheng wrote:
>> Apple folks are also gearing up to push on the PGO front. We are primarily interested in using instrumentation, rather than sampling, to collect profile info. However, I suspect the way profile ended up being used in the various optimization and codegen passes would be largely similar. 
>> 
> 
> Excellent!  We are initially interested in instrumentation, as well.  This is where we draw most of our performance with GCC. Sampling is showing a lot of promise, however.  And it really is not much different than instrumentation.  Most of what changes is the source of profile data.
> 
>> There is also some interests in pursuing profile directed specialization. But that can wait. I think it makes sense for us to get together and discuss our plans to make sure there won't be duplication of efforts. 
> 
> Sure. My initial plan is fairly simple.  Triage the existing instrumentation code and see what needs fixing.  I'm starting this in the next week or so.  What are your plans?

Your short term plan sounds great. We have some tentative plans build / improve the instrumentation tools and start to enhancing various passes to use profile data. Beyond that, our plan is still vague. Bob, comments?

Evan

> 
> 
> Diego.




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