[PATCH] D15829: [PGO] Clang Option that enables IR level PGO instrumentation

[Rong Xu via cfe-commits]

On Thu, Jan 21, 2016 at 7:32 PM, Sean Silva <chisophugis at gmail.com> wrote:
> silvas added a comment.
>
> @slingn and I had a discussion offline about the potential names and came up with some ideas, but none is a clear winner.
>
> Overall, my feeling is that from a user's perspective, the frontend stuff is probably best referred to as "coverage-based". It's not as clear for the IR-level stuff, but referring to it as the "pgo focused" or "optimization focused" instrumentation might be a way to describe it. E.g. perhaps `-fprofile-instr-method={coverage,optimization}`.
>

Agreed. Frontend instrumentation has a less chance of the mismatch
caused by compiler change. IR-level instrumentation is more for the
PGO optimization. Speed and simplicity are the focus -- that is also
the main reason that we don't split the BB for no-return-calls.

> For now, can we make this a CC1-only option? Then we don't have to hold up the patch review on the driver stuff. Once we have fully integrated the IR-level instrumentation, we can revisit exposing the user-visible name. (as compiler developers, we can of course use the flag freely for integration/testing).

I can do this. I just need to move the option define from Opertion.td
to CC1Options.td. The user would need to use '-Xclang
-fprofile-ir-instr' to invoke.

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> http://reviews.llvm.org/D15829
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