[PATCH] RFC: Enable graphite at -O3 -fprofile_use

Richard Biener rguenther@suse.de
Fri Nov 13 11:32:00 GMT 2015


On Fri, 13 Nov 2015, VandeVondele  Joost wrote:

> I'm all in favour of requiring isl and enabling graphite by default, but 
> would suggest to enable it with -Ofast instead.
> 
> One reason is that certainly extracting testcases from a PGO build is 
> more difficult, and initially there will certainly be miscompiles with 
> graphite (CP2K is right now).
> 
> Furthermore, unless graphite is particularly effective with PGO (does it 
> use average loop trip counts already?), I don't see a particular 
> connection.

The reason to choose FDO was so GRAPHITE can concentrate its computing
budget on the hot parts of a program (which profile estimation isn't
good enough identifying), reducing its compile-time cost.

-Ofast isn't supposed to enable passes over -O3 so you're suggesting
to enable it with -O3 which I think is a bit premature.  But we can
try doing that and revert at the end of stage3 if problems are just
too big.

Richard.



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