On Sat, Dec 10, 2016 at 10:37:38AM -0600, Segher Boessenkool wrote:
> On Fri, Dec 09, 2016 at 04:23:44PM +0100, Dominik Vogt wrote:
> > 0001-*
> >
> > Deal with mode expanding zero_extracts in change_zero_ext. The
> > patch looks good to me, but not sure whether endianness is
> > handled properly. Is the second argument of gen_rtx_SUBREG
> > correct?
>
> > >From 600ed3dadd5bc2568ab53be8466686abaf27ff3f Mon Sep 17 00:00:00 2001
> > From: Dominik Vogt <v...@linux.vnet.ibm.com>
> > Date: Fri, 9 Dec 2016 02:48:30 +0100
> > Subject: [PATCH 1/2] combine: Handle mode expanding zero_extracts in
> > change_zero_ext.
> >
> > Example:
> >
> > (zero_extract:DI (reg:SI)
> > (const_int 24)
> > (const_int 0))
> >
> > -->
> >
> > (and:DI (subreg:DI (lshiftrt:SI (reg:SI) (const_int 8))
> > 0)
> > (const_int 16777215))
> > ---
> > gcc/combine.c | 12 +++++++++---
> > 1 file changed, 9 insertions(+), 3 deletions(-)
> >
> > diff --git a/gcc/combine.c b/gcc/combine.c
> > index b429453..e14a08f 100644
> > --- a/gcc/combine.c
> > +++ b/gcc/combine.c
> > @@ -11237,18 +11237,24 @@ change_zero_ext (rtx pat)
> > if (GET_CODE (x) == ZERO_EXTRACT
> > && CONST_INT_P (XEXP (x, 1))
> > && CONST_INT_P (XEXP (x, 2))
> > - && GET_MODE (XEXP (x, 0)) == mode)
> > + && (GET_MODE (XEXP (x, 0)) == mode
> > + || GET_MODE_PRECISION (GET_MODE (XEXP (x, 0)))
> > + < GET_MODE_PRECISION (mode)))
>
> If you make this <= you can collapse the two cases into one.
>
> > {
> > + machine_mode inner_mode = GET_MODE (XEXP (x, 0));
> > +
> > size = INTVAL (XEXP (x, 1));
> >
> > int start = INTVAL (XEXP (x, 2));
> > if (BITS_BIG_ENDIAN)
> > - start = GET_MODE_PRECISION (mode) - size - start;
> > + start = GET_MODE_PRECISION (inner_mode) - size - start;
> >
> > if (start)
> > - x = gen_rtx_LSHIFTRT (mode, XEXP (x, 0), GEN_INT (start));
> > + x = gen_rtx_LSHIFTRT (inner_mode, XEXP (x, 0), GEN_INT (start));
> > else
> > x = XEXP (x, 0);
> > + if (mode != inner_mode)
> > + x = gen_rtx_SUBREG (mode, x, 0);
>
> gen_lowpart_SUBREG instead? It's easier to read, and code a little
> further down does the same thing.
Thanks for taking a look.
> Okay for trunk with those changes (did you bootstrap+regcheck this
> already?)
The patch hasn't got any real testing yet. I'll try to do that
today or tomorrow.
Ciao
Dominik ^_^ ^_^
--
Dominik Vogt
IBM Germany
