[LLVMdev] RFC - Profile Guided Optimization in LLVM

[Jakob Stoklund Olesen]

On Jun 18, 2013, at 11:19 AM, Bob Wilson <bob.wilson at apple.com> wrote:

> The missing piece is adding per-function metadata to record the execution counts.  We had planned to add that along with the branch probabilities but haven't gotten it done yet.  You can see the lack of it in BlockFrequency::getEntryFrequency(), which just returns a constant value.  We will want that to allow comparing profile data across different functions, which you can't easily get from the branch probabilities alone.

Our 64-bit fixpoint representation of block frequencies doesn’t have the dynamic range to do that. See PR16402.

/jakob