[llvm-dev] AutoFDO sample profiles v. SelectInst,

[Sanjay Patel via llvm-dev]

On Fri, Aug 12, 2016 at 12:15 PM, Xinliang David Li via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> +dehao.
>
> There are two potential problems:
>
> 1) the branch gets eliminated in the binary that is being profiled, so
> there is no profile data
>

This seems like a fundamental problem for PGO. Maybe it is also responsible
for this bug: https://llvm.org/bugs/show_bug.cgi?id=27359 ?

Should we limit select optimizations in IR for a PGO-training build? Or
should there be a 'select smasher' pass later in the pipeline that turns
selects into branches for a PGO-training build? (I don't have a good
understanding of PGO, so I'm just throwing out ideas...maybe a better
question is: how do other compilers handle this?)
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