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

[Diego Novillo]

On Mar 13, 2014 6:57 PM, "Bob Wilson" <bob.wilson at apple.com> wrote:

>
> This is a proposal for the instrumentation-based approach that I talked
about at the dev meeting. I don't see how it can share the a file format
with the sample profiler, since the content is fundamentally different.

It is?  But we're fundamentally emitting similar information, right?

Sample counts and instrumentation counts will be different values, sure.
But they convey the same meaning. Higher values mean higher frequency of
execution.

I'm not saying that the file format must be the same. I'm saying that we
should be able to feed block frequency information and branch probability
information in the same way from both instrumentation and sampling data.

So, in the backend pass that reads profile data we should be able to
process both sample data or instrumentation data. The reader layer just
needs to be smart enough to know what it's reading. But it ultimately feeds
the same information in the form of branch weights.

Diego.
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