On Mon, Dec 05, 2016 at 10:22:13AM +0100, Dominik Vogt wrote:
> On Sat, Dec 03, 2016 at 07:19:13PM -0600, Segher Boessenkool wrote:
> > [ I did not see this patch before, sorry. ]
> >
> > This causes the second half of PR78638.
> >
> > On Thu, Dec 01, 2016 at 04:30:08PM +0100, Dominik Vogt wrote:
> > > --- a/gcc/combine.c
> > > +++ b/gcc/combine.c
> > > @@ -5600,6 +5600,18 @@ combine_simplify_rtx (rtx x, machine_mode
> > > op0_mode, int in_dest,
> > > && OBJECT_P (SUBREG_REG (XEXP (x, 0)))))))
> > > {
> > > rtx cond, true_rtx, false_rtx;
> > > + unsigned HOST_WIDE_INT nz;
> > > +
> > > + /* If the operation is an AND wrapped in a SIGN_EXTEND or
> > > ZERO_EXTEND with
> > > + either operand being just a constant single bit value, do nothing since
> > > + IF_THEN_ELSE is likely to increase the expression's complexity. */
> > > + if (HWI_COMPUTABLE_MODE_P (mode)
> > > + && pow2p_hwi (nz = nonzero_bits (x, mode))
> > > + && ! ((code == SIGN_EXTEND || code == ZERO_EXTEND)
> > > + && GET_CODE (XEXP (x, 0)) == AND
> > > + && CONST_INT_P (XEXP (XEXP (x, 0), 0))
> > > + && UINTVAL (XEXP (XEXP (x, 0), 0)) == nz))
> > > + return x;
> >
> > The code does not match the comment: the "!" should not be there. How
> > did it fix anything on s390 *with* that "!"? That does not make much
> > sense.
>
> Sorry for breaking this. With the constant changes in the
> patterns this is supposed to fix it seems I've lost track of the
> status quo. I'll check what went wrong with the patch; in the
> mean time Andreas will revert this, or if it's urgent, feel free
> to do that yourself.
I have tested that removing that ! cures all regressions. I do not
know if it still fixes what this patch intended to fix, of course.
Segher
