[LLVMdev] RFC: Binary format for instrumentation based profiling data

[Bob Wilson]

On Apr 16, 2014, at 2:01 PM, Chandler Carruth <chandlerc at google.com> wrote:

> 
> On Wed, Apr 16, 2014 at 10:48 AM, Bob Wilson <bob.wilson at apple.com> wrote:
> We need to settle of a file format ASAP for our internal work, but from the perspective of the LLVM community, it makes sense to me that this should remain wide open to change, at least until it goes out in an open-source LLVM release.
> 
> Ok, I don't really know how to reconcile this.
> 
> Is it fine to make breaking, backwards incompatible changes to the file format in the coming months or not?

I would really like it if we can avoid making those kinds of changes, but I don’t know how to justify that from an open-source LLVM project perspective.

I can’t expect you to care about Apple’s release schedules but neither can I change them. It would be nice if the open-source version of LLVM can work with the PGO profile data used by Apple (especially because it seems that you guys are taking a totally different approach to PGO which won’t even use these same files). If we can get a “good enough” solution into trunk now, and if we can continue to provide support for that format, then we can make that work. If you really think it’s important to continue iterating on the file format, without adding support for reading the earlier format, then we’ll lose that. It would be unfortunate for the community IMO, but you may not agree.
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