[LLVMdev] RFC - Profile Guided Optimization in LLVM

[Evan Cheng]

Yes. But I'd like to see us tackling these as part two of PGO push. The question is what designs we would have to decide on now to prevent re-design / re-implement later. 

Evan

Sent from my iPad

On Jun 14, 2013, at 12:10 PM, Mark Lacey <mark.lacey at apple.com> wrote:

> 
> On Jun 14, 2013, at 10:56 AM, Krzysztof Parzyszek <kparzysz at codeaurora.org> wrote:
>> 
>> * Function argument value profiling:
>> - Is the function called with a small set of values for the parameters?
>> - Is there any value that is particularly frequent for any of the arguments?
>> - If the function takes pointers, are the pointers usually aligned?
>> - If the function takes pointers, are they aliased?
>> - etc.
> 
> More generally it can be useful to collect value data for things like:
> - switch values, in order to split off one or more dominant values for an explicit check prior to a table look-up or binary-search through all the cases
> - function pointers, to make it possible to explicitly check against a very common pointer value so that the generated code can do a direct call to, or inline, the specific function (including virtual functions)
> 
>> * Path profiling:
>> - Correlation between branches, function calls, etc.
> 
> If interprocedural path profiling information is gathered, that should also be usable as a source for generating context-sensitive call graph profile data.
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev