Re: [PATCH] tree-optimization/109304 - properly handle instrumented aliases

[Richard Biener <rguenther@suse.de>]

On Tue, 4 Apr 2023, Jan Hubicka wrote:

> > On Tue, Apr 04, 2023 at 01:21:40AM +0200, Jan Hubicka via Gcc-patches wrote:
> > > It is however really side case and I am worried about dropping
> > > pure/const from builtin declarations...
> > 
> > Yeah, that can certainly break stuff.  See e.g. the recently fixed
> > ICE when memcmp wasn't pure in PR109258.
> 
> Yep, i think itis better to poke about this in stage1 (it is a can of
> worms).  Clearly we have conflict here: if memcmp is implemented locally
> one can construct a testcase where profile would be rejected on
> -fprofile-use time if const flag is not cleared :(.  But it should be
> rare thing happening in practice.

If we have a locally implemented memcmp then calls to it shouldn't
be marked 'built-in' ...   But then when the compiler itself
creates a memcmp call it would need to resolve to a not instrumented
library copy, or alternatively we should tell the compiler it cannot
emit such a call (but for some builtins not being able to emit them
might prove interesting).

Richard.