[RFC][PR88838][SVE] Use 32-bit WHILELO in LP64 mode

[Kugan Vivekanandarajah]

Hi Richard,

On Thu, 6 Jun 2019 at 22:07, Richard Sandiford
<richard.sandiford@arm.com> wrote:
>
> Kugan Vivekanandarajah <kugan.vivekanandarajah@linaro.org> writes:
> > Hi Richard,
> >
> > On Thu, 6 Jun 2019 at 19:35, Richard Sandiford
> > <richard.sandiford@arm.com> wrote:
> >>
> >> Kugan Vivekanandarajah <kugan.vivekanandarajah@linaro.org> writes:
> >> > Hi Richard,
> >> >
> >> > Thanks for the review. Attached is the latest patch.
> >> >
> >> > For testcase like cond_arith_1.c, with the patch, gcc ICE in fwprop. I
> >> > am limiting fwprop in cases like this. Is there a better fix for this?
> >> > index cf2c9de..2c99285 100644
> >> > --- a/gcc/fwprop.c
> >> > +++ b/gcc/fwprop.c
> >> > @@ -1358,6 +1358,15 @@ forward_propagate_and_simplify (df_ref use,
> >> > rtx_insn *def_insn, rtx def_set)
> >> >    else
> >> >      mode = GET_MODE (*loc);
> >> >
> >> > +  /* TODO. We can't get the mode for
> >> > +     (set (reg:VNx16BI 109)
> >> > +          (unspec:VNx16BI [
> >> > +        (reg:SI 131)
> >> > +        (reg:SI 106)
> >> > +           ] UNSPEC_WHILE_LO))
> >> > +     Thus, bailout when it is UNSPEC and MODEs are not compatible.  */
> >> > +  if (GET_MODE_CLASS (mode) != GET_MODE_CLASS (GET_MODE (reg)))
> >> > +    return false;
> >> >    new_rtx = propagate_rtx (*loc, mode, reg, src,
> >> >                   optimize_bb_for_speed_p (BLOCK_FOR_INSN (use_insn)));
> >>
> >> What specifically goes wrong?  The unspec above isn't that unusual --
> >> many unspecs have different modes from their inputs.
> >
> > cond_arith_1.c:38:1: internal compiler error: in paradoxical_subreg_p,
> > at rtl.h:3130
> > 0x135f1d3 paradoxical_subreg_p(machine_mode, machine_mode)
> >         ../../88838/gcc/rtl.h:3130
> > 0x135f1d3 propagate_rtx
> >         ../../88838/gcc/fwprop.c:683
> > 0x135f4a3 forward_propagate_and_simplify
> >         ../../88838/gcc/fwprop.c:1371
> > 0x135f4a3 forward_propagate_into
> >         ../../88838/gcc/fwprop.c:1430
> > 0x135fdcb fwprop
> >         ../../88838/gcc/fwprop.c:1519
> > 0x135fdcb execute
> >         ../../88838/gcc/fwprop.c:1550
> > Please submit a full bug report,
> > with preprocessed source if appropriate.
> >
> >
> > in forward_propagate_and_simplify
> >
> > use_set:
> > (set (reg:VNx16BI 96 [ loop_mask_52 ])
> >     (unspec:VNx16BI [
> >             (reg:SI 92 [ _3 ])
> >             (reg:SI 95 [ niters.36 ])
> >         ] UNSPEC_WHILE_LO))
> >
> > reg:
> > (reg:SI 92 [ _3 ])
> >
> > *loc:
> > (unspec:VNx16BI [
> >         (reg:SI 92 [ _3 ])
> >         (reg:SI 95 [ niters.36 ])
> >     ] UNSPEC_WHILE_LO)
> >
> > src:
> > (subreg:SI (reg:DI 136 [ ivtmp_101 ]) 0)
> >
> > use_insn:
> > (insn 87 86 88 4 (parallel [
> >             (set (reg:VNx16BI 96 [ loop_mask_52 ])
> >                 (unspec:VNx16BI [
> >                         (reg:SI 92 [ _3 ])
> >                         (reg:SI 95 [ niters.36 ])
> >                     ] UNSPEC_WHILE_LO))
> >             (clobber (reg:CC 66 cc))
> >         ]) 4255 {while_ultsivnx16bi}
> >      (expr_list:REG_UNUSED (reg:CC 66 cc)
> >         (nil)))
> >
> > I think we calculate the mode to be VNx16BI which is wrong?
> > because of which in propgate_rtx,   !paradoxical_subreg_p (mode,
> > GET_MODE (SUBREG_REG (new_rtx)))))  ICE
>
> Looks like something I hit on the ACLE branch, but didn't have a
> non-ACLE reproducer for (see 065881acf0de35ff7818c1fc92769e1c106e1028).
>
> Does the attached work?  The current call is wrong because "mode"
> is the mode of "x", not the mode of "new_rtx".

Yes, attached patch works for this testcase. Are you planning to
commit it to trunk. I will wait for this.

Thanks,
Kugan
>
> Thanks,
> Richard
>
>
> 2019-06-06  Richard Sandiford  <richard.sandiford@arm.com>
>
> gcc/
>         * fwprop.c (propagate_rtx): Fix call to paradoxical_subreg_p.
>
> Index: gcc/fwprop.c
> ===================================================================
> --- gcc/fwprop.c        2019-03-08 18:14:25.333011645 +0000
> +++ gcc/fwprop.c        2019-06-06 13:04:34.423476690 +0100
> @@ -680,7 +680,7 @@ propagate_rtx (rtx x, machine_mode mode,
>        || CONSTANT_P (new_rtx)
>        || (GET_CODE (new_rtx) == SUBREG
>           && REG_P (SUBREG_REG (new_rtx))
> -         && !paradoxical_subreg_p (mode, GET_MODE (SUBREG_REG (new_rtx)))))
> +         && !paradoxical_subreg_p (new_rtx)))
>      flags |= PR_CAN_APPEAR;
>    if (!varying_mem_p (new_rtx))
>      flags |= PR_HANDLE_MEM;