On Thu, Dec 15, 2016 at 09:55:52AM +0100, Dominik Vogt wrote:
> > > Bootstrapped and regression tested on s390x and s390. (Targets
> > > with risbg-like instructions (Power, others?) may need some
> > > tuning.)
> >
> > But, it is also possible I missed some. So please wait until I have
> > tested it.
> >
> > > diff --git a/gcc/combine.c b/gcc/combine.c
> > > index 19851a2..5ebf31c 100644
> > > --- a/gcc/combine.c
> > > +++ b/gcc/combine.c
> > > @@ -11280,8 +11280,13 @@ change_zero_ext (rtx pat)
> > > else
> > > continue;
> > >
> > > - wide_int mask = wi::mask (size, false, GET_MODE_PRECISION (mode));
> > > - x = gen_rtx_AND (mode, x, immed_wide_int_const (mask, mode));
> > > + if (!(GET_CODE (x) == LSHIFTRT
> > > + && CONST_INT_P (XEXP (x, 1))
> > > + && size + INTVAL (XEXP (x, 1)) == GET_MODE_PRECISION (mode)))
> > > + {
> > > + wide_int mask = wi::mask (size, false, GET_MODE_PRECISION (mode));
> > > + x = gen_rtx_AND (mode, x, immed_wide_int_const (mask, mode));
> > > + }
> >
> > One could argue that this should have been an lshiftrt in the first place
> > then, not a zero_ext*. Hrm.
>
> This one
>
> void g2(ui64 *pl, i32 seed)
> {
> seed = 69607 * seed;
> pl[0] = (seed >> 8) & 0xffffff;
> }
>
> generates
>
> (zero_extract:DI (reg:SI 75 [ seed ])
> (const_int 24 [0x18])
> (const_int 0 [0]))
>
> on s390x.
Ah, right, it changes mode as well. I see.
Tested on powerpc64-linux {-m32,-m64}, no new failures. The patch is
okay for trunk. Thanks!
Segher
