This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH] Improve x % y to x VRP optimization (PR tree-optimization/79408)
On Sun, 12 Feb 2017, Marc Glisse wrote:
> On Sun, 12 Feb 2017, Marc Glisse wrote:
>
> > On Tue, 7 Feb 2017, Jakub Jelinek wrote:
> >
> > > * tree-vrp.c (simplify_div_or_mod_using_ranges): If op1 is not
> > > constant, but SSA_NAME with a known integer range, use the minimum
> > > of that range instead of op1 to determine if modulo can be replaced
> > > with its first operand.
> >
> > Would it make sense to use something like the operand_less_p helper so we
> > would also handle an INTEGER_CST lhs?
>
> Oops, operand_less_p is just a helper for compare_values_warnv and even that
> one doesn't seem to use ranges, so there may not already be a nice function we
> can call (?). The idea remains that reusing such code would help handle more
> cases (it may even handle a few symbolic cases).
Yeah, we only have the compare_range_with_value / compare_ranges functions
and those require you to "expand" the value you have a range for first.
Richard.
> > unsigned f(unsigned x){
> > if(x<42)return 18;
> > return 33%x;
> > }
>
>
--
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)