On Tue, 30 Jun 2015, Marek Polacek wrote:
> On Tue, Jun 30, 2015 at 11:08:35AM +0200, Marc Glisse wrote:
> > On Tue, 30 Jun 2015, Marek Polacek wrote:
> >
> > >This moves a simple optimization. Here it's plain to see how :c
> > >removes the need to duplicate code to handle commutativity.
> >
> > Note that the same transformation would work for plus and xor.
>
> Sounds like a good follow-up. I think moving from fold-const.c to
> match.pd ought to be 1:1 for clarity.
Yes, I agree fully here.
> I'll prepare a patch to also
> handle +/^.
Thanks.
> > >I put some more converts into the pattern, but then it's turned
> > >out that I also need the tree_nop_conversion_p (otherwise we'd
> > >regress binop-notor2.c that uses booleans).
> >
> > I don't really see why removing tree_nop_conversion_p would regress anything
> > (though you would probably need to build the all_ones constant in TREE_TYPE
> > (@0) and convert that to type). For my curiosity, could you explain a bit
> > more?
>
> This wasn't all that clear to me. The testcase in question is
>
> int
> foo (_Bool a, _Bool b)
> {
> return (a | (a == 0)) | ((b ^ 1) | b);
> }
>
> this ought to be simplified to "return 1". Through various folding we
> arrive at
>
> (int) ~b | (int) b
>
> so we'd turn that into -1 (all_ones_cst of type int). But for boolean b
> "~b | b" is always 1, right?
Actually our bools are signed ;) Even for unsigned bools we'd
then simply build '1' via build_all_ones_cst.
Richard.
