[LLVMdev] Recent changes in -gmlt break sample profiling

Reid Kleckner rnk at google.com
Sun Oct 26 15:51:45 PDT 2014


On Fri, Oct 24, 2014 at 4:06 PM, Xinliang David Li <xinliangli at gmail.com>
wrote:

> Diego,
>
> I think sampleFDO needs to be designed in a way which can protect itself
> from future breakage like this. The roots in the unnecessary dependency of
> sample FDO on gmlt setting. It is totally reasonable to tune debug binary
> size by changes like this.


FWIW, it's not 100% clear to me that this is the right change. Might be
worth chatting about on Monday.


> The right way is to fix this is to introduce an internal -g<...> flag for
> use by sampleFDO -- it will have a fixed definition of what needs to be
> emitted.
>

This doesn't seem worth having an internal flag for. Google is probably the
primary consumer of Clang's -gline-tables-only data. If it doesn't meet our
needs, we can lobby to make it behave the way we need it to.
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