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

[Diego Novillo]

On Thu, Mar 13, 2014 at 9:19 PM, Justin Bogner <mail at justinbogner.com>wrote:

>
> The instrumentation based profiling is done in the front end, and the
> counters are related to parts do the AST. Their isn't enough information
> for a backend pass to map them to *anything*. We feed block frequency and
> branch probability through metadata, much like the sampling based approach,
> but it happens during irgen in the front end, rather than in a backend pass.
>

Ah, OK. At least we get the annotations through to the backend. So,
instrumentation gathers both block and edge weights? Or do you derive edge
weights from blocks?


>
> While it might be possible to translate the instrumentation format to the
> profile format, it wouldn't be possible to go the other way, and the
> translation would be imperfect.
>

I'm only interested in passing the instrumentation down to the back end.
Are you folks thinking of doing other kinds of instrumentation? (value
profiling, for example).


Thanks. Diego.
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