Re: [PATCH] rs6000: suboptimal code for returning bool value on target ppc

[Richard Biener <richard.guenther@gmail.com>]

On Thu, Mar 16, 2023 at 11:12 AM Ajit Agarwal <aagarwa1@linux.ibm.com> wrote:
>
>
> Hello Richard:
>
> On 16/03/23 3:22 pm, Richard Biener wrote:
> > On Thu, Mar 16, 2023 at 9:19 AM Ajit Agarwal <aagarwa1@linux.ibm.com> wrote:
> >>
> >>
> >>
> >> On 16/03/23 1:44 pm, Richard Biener wrote:
> >>> On Thu, Mar 16, 2023 at 9:11 AM Ajit Agarwal <aagarwa1@linux.ibm.com> wrote:
> >>>>
> >>>> Hello Richard:
> >>>>
> >>>> On 16/03/23 1:10 pm, Richard Biener wrote:
> >>>>> On Thu, Mar 16, 2023 at 6:21 AM Ajit Agarwal via Gcc-patches
> >>>>> <gcc-patches@gcc.gnu.org> wrote:
> >>>>>>
> >>>>>> Hello All:
> >>>>>>
> >>>>>>
> >>>>>> This patch eliminates unnecessary zero extension instruction from power generated assembly.
> >>>>>> Bootstrapped and regtested on powerpc64-linux-gnu.
> >>>>>
> >>>>> What makes this so special that we cannot deal with it from generic code?
> >>>>> In particular we do have the REE pass, why is target specific
> >>>>> knowledge neccessary
> >>>>> to eliminate the extension?
> >>>>>
> >>>>
> >>>> For returning bool values and comparision with integers generates the following by all the rtl passes.
> >>>>
> >>>> set compare (subreg)
> >>>> set if_then_else
> >>>> Convert SImode -> QImode
> >>>> set zero_extend to SImode from QImode
> >>>> set return value 0 in one path of cfg.
> >>>> set return value 1 in other path of cfg.
> >>>>
> >>>> This pass replaces the above zero extension and conversion from QImode to DImode with copy operation to keep QImode in 64 bit registers in powerpc target.
> >>>
> >>> Sorry, I can't parse that - as there's no testcase with the patch I
> >>> cannot even try to see what the actual RTL
> >>> looks like (without the pass).
> >>>
> >>
> >> Here is the PR with bugzilla.
> >> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103784
> >>
> >> I can add the attached testcase with this PR in the patch.
> >
> > I don't see any zero-extends there.
> >
>
> Here is the testcase.
>
>
> bool (int a, int b)
> {
>           if (a > 2)
>                       return false;
>            if (b < 10)
>                        return true;
>              return false;
> }
>
> compiled with gcc -O3 -m64 testcase.cc -mcpu=power9 -save-temps.
>
> Here is the rtl after cse.
> (note 12 11 15 3 [bb 3] NOTE_INSN_BASIC_BLOCK)
> (insn 15 12 16 3 (set (reg:CC 123)
>         (compare:CC (subreg/s/u:SI (reg/v:DI 120 [ b ]) 0)
>             (const_int 9 [0x9]))) "ext.cc":5:5 796 {*cmpsi_signed}
>      (expr_list:REG_DEAD (reg/v:DI 120 [ b ])
>         (nil)))
> (insn 16 15 17 3 (set (reg:SI 124)
>         (const_int 1 [0x1])) "ext.cc":5:5 555 {*movsi_internal1}
>      (nil))
> (insn 17 16 18 3 (set (reg:SI 122)
>         (if_then_else:SI (gt (reg:CC 123)
>                 (const_int 0 [0]))
>             (const_int 0 [0])
>             (reg:SI 124))) "ext.cc":5:5 344 {isel_cc_si}
>      (expr_list:REG_DEAD (reg:SI 124)
>         (expr_list:REG_DEAD (reg:CC 123)
>             (nil))))
> (insn 18 17 32 3 (set (reg:QI 117 [ _1 ])
>         (subreg:QI (reg:SI 122) 0)) "ext.cc":5:5 562 {*movqi_internal}
>      (expr_list:REG_DEAD (reg:SI 122)
>         (nil)))
>       ; pc falls through to BB 5
> (code_label 32 18 31 4 3 (nil) [1 uses])
> (note 31 32 5 4 [bb 4] NOTE_INSN_BASIC_BLOCK)
> (insn 5 31 19 4 (set (reg:QI 117 [ _1 ])
>         (const_int 0 [0])) "ext.cc":4:16 562 {*movqi_internal}
>      (nil))
> (code_label 19 5 20 5 2 (nil) [0 uses])
> (note 20 19 21 5 [bb 5] NOTE_INSN_BASIC_BLOCK)
> (insn 21 20 22 5 (set (reg:DI 126 [ _1 ])
>         (zero_extend:DI (reg:QI 117 [ _1 ]))) "ext.cc":8:1 5 {zero_extendqidi2}
>      (expr_list:REG_DEAD (reg:QI 117 [ _1 ])
>         (nil)))
> (insn 22 21 26 5 (set (reg:DI 118 [ <retval> ])
>         (reg:DI 126 [ _1 ])) "ext.cc":8:1 681 {*movdi_internal64}
>      (expr_list:REG_DEAD (reg:DI 126 [ _1 ])
>         (nil)))
> (insn 26 22 27 5 (set (reg/i:DI 3 3)
>         (reg:DI 126 [ _1 ])) "ext.cc":8:1 681 {*movdi_internal64}
>      (expr_list:REG_DEAD (reg:DI 118 [ <retval> ])
>         (nil)))
> (insn 27 26 0 5 (use (reg/i:DI 3 3)) "ext.cc":8:1 -1
>      (nil))

But after combine there's just

(note 6 0 38 2 [bb 2] NOTE_INSN_BASIC_BLOCK)
(insn 38 6 2 2 (set (reg:DI 126)
        (reg:DI 3 3 [ a ])) "t.c":3:1 634 {*movdi_internal64}
     (expr_list:REG_DEAD (reg:DI 3 3 [ a ])
        (nil)))
(note 2 38 39 2 NOTE_INSN_DELETED)
(insn 39 2 3 2 (set (reg:DI 127)
        (reg:DI 4 4 [ b ])) "t.c":3:1 634 {*movdi_internal64}
     (expr_list:REG_DEAD (reg:DI 4 4 [ b ])
        (nil)))
(insn 3 39 4 2 (set (reg/v:DI 119 [ b ])
        (reg:DI 127)) "t.c":3:1 634 {*movdi_internal64}
     (expr_list:REG_DEAD (reg:DI 127)
        (nil)))
(note 4 3 10 2 NOTE_INSN_FUNCTION_BEG)
(insn 10 4 11 2 (set (reg:CC 120)
        (compare:CC (subreg/s/u:SI (reg:DI 126) 0)
            (const_int 2 [0x2]))) "t.c":4:6 755 {*cmpsi_signed}
     (expr_list:REG_DEAD (reg:DI 126)
        (nil)))
(jump_insn 11 10 12 2 (set (pc)
        (if_then_else (gt (reg:CC 120)
                (const_int 0 [0]))
            (label_ref:DI 32)
            (pc))) "t.c":4:6 838 {*cbranch}
     (expr_list:REG_DEAD (reg:CC 120)
        (int_list:REG_BR_PROB 365072228 (nil)))
 -> 32)
(note 12 11 15 3 [bb 3] NOTE_INSN_BASIC_BLOCK)
(note 15 12 16 3 NOTE_INSN_DELETED)
(note 16 15 17 3 NOTE_INSN_DELETED)
(note 17 16 19 3 NOTE_INSN_DELETED)
(insn 19 17 32 3 (parallel [
            (set (reg:DI 117 [ <retval> ])
                (le:DI (subreg/s/u:SI (reg/v:DI 119 [ b ]) 0)
                    (const_int 9 [0x9])))
            (clobber (scratch:DI))
            (clobber (scratch:DI))
            (clobber (scratch:CC))
        ]) "t.c":6:6 783 {ledisi2_isel}
     (expr_list:REG_DEAD (reg/v:DI 119 [ b ])
        (nil)))
      ; pc falls through to BB 5
(code_label 32 19 31 4 3 (nil) [1 uses])
(note 31 32 5 4 [bb 4] NOTE_INSN_BASIC_BLOCK)
(insn 5 31 20 4 (set (reg:DI 117 [ <retval> ])
        (const_int 0 [0])) "t.c":5:12 634 {*movdi_internal64}
     (nil))
(code_label 20 5 21 5 2 (nil) [0 uses])
(note 21 20 26 5 [bb 5] NOTE_INSN_BASIC_BLOCK)
(insn 26 21 27 5 (set (reg/i:DI 3 3)
        (reg:DI 117 [ <retval> ])) "t.c":9:1 634 {*movdi_internal64}
     (expr_list:REG_DEAD (reg:DI 117 [ <retval> ])
        (nil)))
(insn 27 26 0 5 (use (reg/i:DI 3 3)) "t.c":9:1 -1
     (nil))

and we get

foo:
.LFB0:
        .cfi_startproc
        cmpwi 0,3,2
        bgt 0,.L3
        cmpwi 0,4,9
        li 3,1
        isel 3,0,3,1
        blr
        .p2align 4,,15
.L3:
        li 3,0
        blr

where I don't see what we can do better (ok, not knowing ppc very much)

>
> Thanks & Regards
> Ajit
>
> >> Thanks & Regards
> >> Ajit
> >>> Richard.
> >>>
> >>>> Thanks & Regards
> >>>> Ajit
> >>>>>> +  In cfgexpand pass QImode is generated with
> >>>>>> +  bool register value and this pass uses QI
> >>>>>> +  as 64 bit registers.
> >>>>>> +
> >>>>
> >>>>>>         rs6000: suboptimal code for returning bool value on target ppc.
> >>>>>>
> >>>>>>         New pass to eliminate unnecessary zero extension. This pass
> >>>>>>         is registered after cse rtl pass.
> >>>>>>
> >>>>>>         2023-03-16  Ajit Kumar Agarwal  <aagarwa1@linux.ibm.com>
> >>>>>>
> >>>>>> gcc/ChangeLog:
> >>>>>>
> >>>>>>         * config/rs6000/rs6000-passes.def: Registered zero elimination
> >>>>>>         pass.
> >>>>>>         * config/rs6000/rs6000-zext-elim.cc: Add new pass.
> >>>>>>         * config.gcc: Add new executable.
> >>>>>>         * config/rs6000/rs6000-protos.h: Add new prototype for zero
> >>>>>>         elimination pass.
> >>>>>>         * config/rs6000/rs6000.cc: Add new prototype for zero
> >>>>>>         elimination pass.
> >>>>>>         * config/rs6000/t-rs6000: Add new rule.
> >>>>>>         * expr.cc: Modified gcc assert.
> >>>>>>         * explow.cc: Modified gcc assert.
> >>>>>>         * optabs.cc: Modified gcc assert.
> >>>>>> ---
> >>>>>>  gcc/config.gcc                        |   4 +-
> >>>>>>  gcc/config/rs6000/rs6000-passes.def   |   2 +
> >>>>>>  gcc/config/rs6000/rs6000-protos.h     |   1 +
> >>>>>>  gcc/config/rs6000/rs6000-zext-elim.cc | 361 ++++++++++++++++++++++++++
> >>>>>>  gcc/config/rs6000/rs6000.cc           |   2 +
> >>>>>>  gcc/config/rs6000/t-rs6000            |   5 +
> >>>>>>  gcc/explow.cc                         |   3 +-
> >>>>>>  gcc/expr.cc                           |   4 +-
> >>>>>>  gcc/optabs.cc                         |   3 +-
> >>>>>>  9 files changed, 379 insertions(+), 6 deletions(-)
> >>>>>>  create mode 100644 gcc/config/rs6000/rs6000-zext-elim.cc
> >>>>>>
> >>>>>> diff --git a/gcc/config.gcc b/gcc/config.gcc
> >>>>>> index da3a6d3ba1f..e8ac9d882f0 100644
> >>>>>> --- a/gcc/config.gcc
> >>>>>> +++ b/gcc/config.gcc
> >>>>>> @@ -503,7 +503,7 @@ or1k*-*-*)
> >>>>>>         ;;
> >>>>>>  powerpc*-*-*)
> >>>>>>         cpu_type=rs6000
> >>>>>> -       extra_objs="rs6000-string.o rs6000-p8swap.o rs6000-logue.o"
> >>>>>> +       extra_objs="rs6000-string.o rs6000-p8swap.o rs6000-zext-elim.o rs6000-logue.o"
> >>>>>>         extra_objs="${extra_objs} rs6000-call.o rs6000-pcrel-opt.o"
> >>>>>>         extra_objs="${extra_objs} rs6000-builtins.o rs6000-builtin.o"
> >>>>>>         extra_headers="ppc-asm.h altivec.h htmintrin.h htmxlintrin.h"
> >>>>>> @@ -538,7 +538,7 @@ riscv*)
> >>>>>>         ;;
> >>>>>>  rs6000*-*-*)
> >>>>>>         extra_options="${extra_options} g.opt fused-madd.opt rs6000/rs6000-tables.opt"
> >>>>>> -       extra_objs="rs6000-string.o rs6000-p8swap.o rs6000-logue.o"
> >>>>>> +       extra_objs="rs6000-string.o rs6000-p8swap.o rs6000-zext-elim.o rs6000-logue.o"
> >>>>>>         extra_objs="${extra_objs} rs6000-call.o rs6000-pcrel-opt.o"
> >>>>>>         target_gtfiles="$target_gtfiles \$(srcdir)/config/rs6000/rs6000-logue.cc \$(srcdir)/config/rs6000/rs6000-call.cc"
> >>>>>>         target_gtfiles="$target_gtfiles \$(srcdir)/config/rs6000/rs6000-pcrel-opt.cc"
> >>>>>> diff --git a/gcc/config/rs6000/rs6000-passes.def b/gcc/config/rs6000/rs6000-passes.def
> >>>>>> index ca899d5f7af..d7500feddf1 100644
> >>>>>> --- a/gcc/config/rs6000/rs6000-passes.def
> >>>>>> +++ b/gcc/config/rs6000/rs6000-passes.def
> >>>>>> @@ -28,6 +28,8 @@ along with GCC; see the file COPYING3.  If not see
> >>>>>>       The power8 does not have instructions that automaticaly do the byte swaps
> >>>>>>       for loads and stores.  */
> >>>>>>    INSERT_PASS_BEFORE (pass_cse, 1, pass_analyze_swaps);
> >>>>>> +  INSERT_PASS_AFTER (pass_cse, 1, pass_analyze_zext);
> >>>>>> +
> >>>>>>
> >>>>>>    /* Pass to do the PCREL_OPT optimization that combines the load of an
> >>>>>>       external symbol's address along with a single load or store using that
> >>>>>> diff --git a/gcc/config/rs6000/rs6000-protos.h b/gcc/config/rs6000/rs6000-protos.h
> >>>>>> index 1a4fc1df668..f6cf2d673d4 100644
> >>>>>> --- a/gcc/config/rs6000/rs6000-protos.h
> >>>>>> +++ b/gcc/config/rs6000/rs6000-protos.h
> >>>>>> @@ -340,6 +340,7 @@ namespace gcc { class context; }
> >>>>>>  class rtl_opt_pass;
> >>>>>>
> >>>>>>  extern rtl_opt_pass *make_pass_analyze_swaps (gcc::context *);
> >>>>>> +extern rtl_opt_pass *make_pass_analyze_zext (gcc::context *);
> >>>>>>  extern rtl_opt_pass *make_pass_pcrel_opt (gcc::context *);
> >>>>>>  extern bool rs6000_sum_of_two_registers_p (const_rtx expr);
> >>>>>>  extern bool rs6000_quadword_masked_address_p (const_rtx exp);
> >>>>>> diff --git a/gcc/config/rs6000/rs6000-zext-elim.cc b/gcc/config/rs6000/rs6000-zext-elim.cc
> >>>>>> new file mode 100644
> >>>>>> index 00000000000..777c7a5a387
> >>>>>> --- /dev/null
> >>>>>> +++ b/gcc/config/rs6000/rs6000-zext-elim.cc
> >>>>>> @@ -0,0 +1,361 @@
> >>>>>> +/* Subroutine to eliminate redundant zero extend for power architecture.
> >>>>>> +   Copyright (C) 1991-2023 Free Software Foundation, Inc.
> >>>>>> +
> >>>>>> +   This file is part of GCC.
> >>>>>> +
> >>>>>> +   GCC is free software; you can redistribute it and/or modify it
> >>>>>> +   under the terms of the GNU General Public License as published
> >>>>>> +   by the Free Software Foundation; either version 3, or (at your
> >>>>>> +   option) any later version.
> >>>>>> +
> >>>>>> +   GCC is distributed in the hope that it will be useful, but WITHOUT
> >>>>>> +   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
> >>>>>> +   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
> >>>>>> +   License for more details.
> >>>>>> +
> >>>>>> +   You should have received a copy of the GNU General Public License
> >>>>>> +   along with GCC; see the file COPYING3.  If not see
> >>>>>> +   <http://www.gnu.org/licenses/>.  */
> >>>>>> +
> >>>>>> +/* This pass remove unnecessary zero extension instruction from
> >>>>>> +  power generated assembly. This pass is register after cse
> >>>>>> +  pass.
> >>>>>> +  Identifies the following sequence of instruction after cse
> >>>>>> +  rtl pass.
> >>>>>> +
> >>>>>> +  set compare (subreg)
> >>>>>> +  set if_then_else
> >>>>>> +  set SImode -> QImode
> >>>>>> +  set zero_extend to DImode from QImode
> >>>>>> +  set return value 0 in one path of cfg.
> >>>>>> +  set return value 1 in other path of cfg.
> >>>>>> +
> >>>>>> +  In cfgexpand pass QImode is generated with
> >>>>>> +  bool register value and this pass uses QI
> >>>>>> +  as 64 bit registers.
> >>>>>> +
> >>>>>> +  This pass replace copy operation from QImode to DImode
> >>>>>> +  and return appropriate return values.*/
> >>>>>> +
> >>>>>> +#define IN_TARGET_CODE 1
> >>>>>> +
> >>>>>> +#include "config.h"
> >>>>>> +#include "system.h"
> >>>>>> +#include "coretypes.h"
> >>>>>> +#include "backend.h"
> >>>>>> +#include "rtl.h"
> >>>>>> +#include "tree.h"
> >>>>>> +#include "memmodel.h"
> >>>>>> +#include "df.h"
> >>>>>> +#include "tm_p.h"
> >>>>>> +#include "ira.h"
> >>>>>> +#include "print-tree.h"
> >>>>>> +#include "varasm.h"
> >>>>>> +#include "explow.h"
> >>>>>> +#include "expr.h"
> >>>>>> +#include "output.h"
> >>>>>> +#include "tree-pass.h"
> >>>>>> +
> >>>>>> +/* This is based on the union-find logic in web.cc.  web_entry_base is
> >>>>>> +   defined in df.h.  */
> >>>>>> +class zext_web_entry : public web_entry_base
> >>>>>> +{
> >>>>>> + public:
> >>>>>> +  /* Pointer to the insn.  */
> >>>>>> +  rtx_insn *insn;
> >>>>>> +  unsigned int is_relevant : 1;
> >>>>>> +  /* Set if insn is a load.  */
> >>>>>> +  unsigned int is_load : 1;
> >>>>>> +  /* Set if insn is a store.  */
> >>>>>> +  unsigned int is_store : 1;
> >>>>>> +  unsigned int is_zext :1 ;
> >>>>>> +  unsigned int is_move :1;
> >>>>>> +  unsigned int is_delete_move :1;
> >>>>>> +  /* Set if this insn should be deleted.  */
> >>>>>> +  unsigned int will_delete : 1;
> >>>>>> +  unsigned int will_delete_chances : 1;
> >>>>>> +};
> >>>>>> +
> >>>>>> +/* Checks if instruction is zero extension
> >>>>>> + * with QIMode to DImode.*/
> >>>>>> +static unsigned int
> >>>>>> +insn_is_zext_p(rtx insn)
> >>>>>> +{
> >>>>>> +  rtx body = PATTERN (insn);
> >>>>>> +
> >>>>>> +  if (GET_CODE (body) == SET
> >>>>>> +      && GET_MODE(SET_DEST (body)) == DImode
> >>>>>> +      && GET_CODE(SET_SRC (body)) == ZERO_EXTEND)
> >>>>>> +  {
> >>>>>> +    rtx set = XEXP (SET_SRC (body), 0);
> >>>>>> +
> >>>>>> +    if (REG_P (set))
> >>>>>> +    {
> >>>>>> +      if (GET_MODE (set) == QImode) return 1;
> >>>>>> +    }
> >>>>>> +    else
> >>>>>> +      return 0;
> >>>>>> +  }
> >>>>>> +  return 0;
> >>>>>> +}
> >>>>>> +
> >>>>>> +/* Checks if instruction is SET operation with QImode.*/
> >>>>>> +static unsigned int
> >>>>>> +insn_is_store_p (rtx insn)
> >>>>>> +{
> >>>>>> +  rtx body = PATTERN (insn);
> >>>>>> +  if (GET_CODE (body) == SET
> >>>>>> +      && SUBREG_P(SET_SRC (body))
> >>>>>> +      && !CONST_INT_P(SET_SRC (body))
> >>>>>> +      && GET_MODE(XEXP (SET_SRC (body), 0)) == SImode
> >>>>>> +      && GET_MODE(SET_SRC (body)) == QImode)
> >>>>>> +    return 1;
> >>>>>> +
> >>>>>> +  return 0;
> >>>>>> +}
> >>>>>> +
> >>>>>> +/* Find out zero extension removal candidate with use-def web.*/
> >>>>>> +static void
> >>>>>> +find_zero_ext_elimination_candidate (zext_web_entry *insn_entry,
> >>>>>> +                                    rtx insn, df_ref def)
> >>>>>> +{
> >>>>>> +  struct df_link *link = DF_REF_CHAIN (def);
> >>>>>> +
> >>>>>> +  rtx move_insn = NULL_RTX;
> >>>>>> +  rtx compare_insn = NULL_RTX;
> >>>>>> +
> >>>>>> +  while (link)
> >>>>>> +  {
> >>>>>> +    if (!DF_REF_INSN_INFO (link->ref))
> >>>>>> +      insn_entry[INSN_UID(insn)].will_delete_chances = 0;
> >>>>>> +
> >>>>>> +    if (DF_REF_INSN_INFO (link->ref))
> >>>>>> +      {
> >>>>>> +       rtx use_insn = DF_REF_INSN (link->ref);
> >>>>>> +
> >>>>>> +       if (GET_CODE (PATTERN (use_insn)) == SET
> >>>>>> +           && (GET_CODE (SET_SRC (PATTERN (use_insn))) == IF_THEN_ELSE))
> >>>>>> +         {
> >>>>>> +           if (GET_CODE (PATTERN (insn)) == SET
> >>>>>> +               && GET_CODE (SET_SRC (PATTERN (insn))) == COMPARE)
> >>>>>> +             {
> >>>>>> +               rtx body = XEXP (SET_SRC (PATTERN (insn)), 0);
> >>>>>> +
> >>>>>> +               if (SUBREG_P (body))
> >>>>>> +                 {
> >>>>>> +                   compare_insn = use_insn;
> >>>>>> +                   rtx compare_body = XEXP (SET_SRC (PATTERN (compare_insn)), 0);
> >>>>>> +
> >>>>>> +                   if (compare_insn
> >>>>>> +                       && ((REGNO (XEXP (compare_body, 0)))
> >>>>>> +                               == REGNO (SET_DEST (PATTERN (insn)))))
> >>>>>> +                     insn_entry[INSN_UID(use_insn)].will_delete_chances = 1;
> >>>>>> +                 }
> >>>>>> +              }
> >>>>>> +           }
> >>>>>> +
> >>>>>> +       if (insn_is_store_p(use_insn)
> >>>>>> +           && GET_CODE (PATTERN (insn)) == SET
> >>>>>> +           && (GET_CODE (SET_SRC (PATTERN(insn))) == IF_THEN_ELSE))
> >>>>>> +         {
> >>>>>> +           if (GET_MODE (SET_DEST (PATTERN (insn))) == SImode)
> >>>>>> +             {
> >>>>>> +               if (insn_entry[INSN_UID(insn)].will_delete_chances)
> >>>>>> +                 insn_entry[INSN_UID(use_insn)].will_delete_chances = 1;
> >>>>>> +             }
> >>>>>> +         }
> >>>>>> +
> >>>>>> +       if (insn_is_zext_p (insn))
> >>>>>> +         {
> >>>>>> +           if (GET_CODE (PATTERN (use_insn)) == SET
> >>>>>> +               && REG_P (SET_SRC (PATTERN (use_insn))))
> >>>>>> +             {
> >>>>>> +               if (move_insn
> >>>>>> +                   && REGNO (SET_SRC (PATTERN (use_insn)))
> >>>>>> +                      == REGNO (SET_SRC (PATTERN (move_insn)))
> >>>>>> +                   && insn_entry[INSN_UID(insn)].is_delete_move)
> >>>>>> +                 {
> >>>>>> +                   insn_entry[INSN_UID (insn)].is_move = 1;
> >>>>>> +                   break;
> >>>>>> +                 }
> >>>>>> +                 else if (insn_entry[INSN_UID (insn)].will_delete)
> >>>>>> +                   {
> >>>>>> +                     move_insn = use_insn;
> >>>>>> +                     insn_entry[INSN_UID(insn)].is_delete_move= 1;
> >>>>>> +                   }
> >>>>>> +             }
> >>>>>> +         }
> >>>>>> +
> >>>>>> +       if (insn_is_zext_p (use_insn))
> >>>>>> +         {
> >>>>>> +           insn_entry[INSN_UID (use_insn)].is_zext = 1;
> >>>>>> +           insn_entry[INSN_UID(use_insn)].is_relevant = 1;
> >>>>>> +
> >>>>>> +           if (insn_is_store_p (insn)
> >>>>>> +               && insn_entry[INSN_UID (insn)].will_delete_chances)
> >>>>>> +           {
> >>>>>> +             insn_entry[INSN_UID (use_insn)].will_delete = 1;
> >>>>>> +             insn_entry[INSN_UID (insn)].will_delete = 1;
> >>>>>> +             insn_entry[INSN_UID( insn)].is_store = 1;
> >>>>>> +           }
> >>>>>> +
> >>>>>> +          if (NONDEBUG_INSN_P (use_insn))
> >>>>>> +            unionfind_union (insn_entry + INSN_UID (insn),
> >>>>>> +                             insn_entry + INSN_UID (use_insn));
> >>>>>> +       }
> >>>>>> +      }
> >>>>>> +
> >>>>>> +    link = link->next;
> >>>>>> +  }
> >>>>>> +}
> >>>>>> +
> >>>>>> +/* Replace QImode extensions with copy operations.*/
> >>>>>> +static void
> >>>>>> +replace_marked_insns (zext_web_entry *insn_entry, unsigned i)
> >>>>>> +{
> >>>>>> +  rtx_insn *insn = insn_entry[i].insn;
> >>>>>> +  rtx body = PATTERN (insn);
> >>>>>> +  rtx src_reg;
> >>>>>> +  src_reg = XEXP (SET_SRC (body), 0);
> >>>>>> +  set_mode_and_regno (src_reg, DImode, REGNO(src_reg));
> >>>>>> +
> >>>>>> +  if (GET_MODE(SET_DEST(body)) != DImode)
> >>>>>> +    set_mode_and_regno (SET_DEST(body), DImode, REGNO (SET_DEST (body)));
> >>>>>> +
> >>>>>> +  rtx copy = gen_rtx_SET (SET_DEST (body), src_reg);
> >>>>>> +  rtx_insn *new_insn = emit_insn_before (copy, insn);
> >>>>>> +  set_block_for_insn (new_insn, BLOCK_FOR_INSN (insn));
> >>>>>> +  df_insn_rescan (new_insn);
> >>>>>> +
> >>>>>> +  df_insn_delete (insn);
> >>>>>> +  remove_insn (insn);
> >>>>>> +  insn->set_deleted ();
> >>>>>> +}
> >>>>>> +
> >>>>>> +/* Main entry point for this pass.  */
> >>>>>> +unsigned int
> >>>>>> +rs6000_analyze_zext (function *fun)
> >>>>>> +{
> >>>>>> +  zext_web_entry *insn_entry;
> >>>>>> +  basic_block bb;
> >>>>>> +  rtx_insn *insn, *curr_insn = 0;
> >>>>>> +
> >>>>>> +  /* Dataflow analysis for use-def chains.  */
> >>>>>> +  df_set_flags (DF_RD_PRUNE_DEAD_DEFS);
> >>>>>> +  df_chain_add_problem (DF_DU_CHAIN | DF_UD_CHAIN);
> >>>>>> +  df_analyze ();
> >>>>>> +  df_set_flags (DF_DEFER_INSN_RESCAN);
> >>>>>> +
> >>>>>> +  /* Rebuild ud- and du-chains.  */
> >>>>>> +  df_remove_problem (df_chain);
> >>>>>> +  df_process_deferred_rescans ();
> >>>>>> +  df_set_flags (DF_RD_PRUNE_DEAD_DEFS);
> >>>>>> +  df_chain_add_problem (DF_DU_CHAIN | DF_UD_CHAIN);
> >>>>>> +  df_analyze ();
> >>>>>> +  df_set_flags (DF_DEFER_INSN_RESCAN);
> >>>>>> +
> >>>>>> +  /* Allocate structure to represent webs of insns.  */
> >>>>>> +  insn_entry = XCNEWVEC (zext_web_entry, get_max_uid ());
> >>>>>> +
> >>>>>> +  /* Walk the insns to gather basic data.  */
> >>>>>> +  FOR_ALL_BB_FN (bb, fun)
> >>>>>> +    FOR_BB_INSNS_SAFE (bb, insn, curr_insn)
> >>>>>> +    {
> >>>>>> +      unsigned int uid = INSN_UID (insn);
> >>>>>> +      if (NONDEBUG_INSN_P (insn))
> >>>>>> +       {
> >>>>>> +         insn_entry[uid].insn = insn;
> >>>>>> +
> >>>>>> +         if (GET_CODE (insn) == insn_is_store_p (insn))
> >>>>>> +           {
> >>>>>> +             insn_entry[uid].is_store = 1;
> >>>>>> +             insn_entry[uid].is_relevant = 1;
> >>>>>> +           }
> >>>>>> +
> >>>>>> +         /* Walk the uses and defs to identify the optimization
> >>>>>> +            candidates.*/
> >>>>>> +         struct df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
> >>>>>> +         df_ref mention;
> >>>>>> +
> >>>>>> +         FOR_EACH_INSN_INFO_DEF (mention, insn_info)
> >>>>>> +           {
> >>>>>> +             insn_entry[uid].is_relevant = 1;
> >>>>>> +             insn_entry[uid].is_store = insn_is_store_p (insn);
> >>>>>> +             find_zero_ext_elimination_candidate (insn_entry, insn, mention);
> >>>>>> +           }
> >>>>>> +
> >>>>>> +         if (insn_entry[uid].is_relevant)
> >>>>>> +           {
> >>>>>> +             /* Determine if this is a store.  */
> >>>>>> +             insn_entry[uid].is_store = insn_is_store_p (insn);
> >>>>>> +           }
> >>>>>> +       }
> >>>>>> +     }
> >>>>>> +
> >>>>>> +   unsigned e = get_max_uid (), i;
> >>>>>> +
> >>>>>> +   int store_index = -1;
> >>>>>> +
> >>>>>> +   /* Replace with copy operation.*/
> >>>>>> +   for (i = 0; i < e; ++i)
> >>>>>> +     {
> >>>>>> +       if (insn_entry[i].is_store && insn_entry[i].will_delete)
> >>>>>> +        store_index  = i;
> >>>>>> +
> >>>>>> +       if ((store_index != -1)
> >>>>>> +            && insn_entry[i].is_move && insn_entry[i].will_delete)
> >>>>>> +         {
> >>>>>> +           replace_marked_insns (insn_entry, store_index);
> >>>>>> +           replace_marked_insns (insn_entry, i);
> >>>>>> +         }
> >>>>>> +     }
> >>>>>> +    /* Clean up.  */
> >>>>>> +    free (insn_entry);
> >>>>>> +
> >>>>>> +    return 0;
> >>>>>> +}
> >>>>>> +
> >>>>>> +const pass_data pass_data_analyze_zext =
> >>>>>> +{
> >>>>>> +  RTL_PASS, /* type */
> >>>>>> +  "zext", /* name */
> >>>>>> +  OPTGROUP_NONE, /* optinfo_flags */
> >>>>>> +  TV_NONE, /* tv_id */
> >>>>>> +  0, /* properties_required */
> >>>>>> +  0, /* properties_provided */
> >>>>>> +  0, /* properties_destroyed */
> >>>>>> +  0, /* todo_flags_start */
> >>>>>> +  TODO_df_finish, /* todo_flags_finish */
> >>>>>> +};
> >>>>>> +
> >>>>>> +class pass_analyze_zext : public rtl_opt_pass
> >>>>>> +{
> >>>>>> +public:
> >>>>>> +  pass_analyze_zext(gcc::context *ctxt)
> >>>>>> +    : rtl_opt_pass(pass_data_analyze_zext, ctxt)
> >>>>>> +  {}
> >>>>>> +
> >>>>>> +  /* opt_pass methods: */
> >>>>>> +  virtual bool gate (function *)
> >>>>>> +    {
> >>>>>> +      return (optimize > 0 );
> >>>>>> +    }
> >>>>>> +
> >>>>>> +  virtual unsigned int execute (function *fun)
> >>>>>> +    {
> >>>>>> +      return rs6000_analyze_zext (fun);
> >>>>>> +    }
> >>>>>> +
> >>>>>> +  opt_pass *clone ()
> >>>>>> +    {
> >>>>>> +      return new pass_analyze_zext (m_ctxt);
> >>>>>> +    }
> >>>>>> +
> >>>>>> +}; // class pass_analyze_zext
> >>>>>> +
> >>>>>> +rtl_opt_pass *
> >>>>>> +make_pass_analyze_zext (gcc::context *ctxt)
> >>>>>> +{
> >>>>>> +  return new pass_analyze_zext (ctxt);
> >>>>>> +}
> >>>>>> +
> >>>>>> diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
> >>>>>> index 8e0b0d022db..6541334bf2d 100644
> >>>>>> --- a/gcc/config/rs6000/rs6000.cc
> >>>>>> +++ b/gcc/config/rs6000/rs6000.cc
> >>>>>> @@ -1178,6 +1178,8 @@ static bool rs6000_secondary_reload_move (enum rs6000_reg_type,
> >>>>>>                                           bool);
> >>>>>>  rtl_opt_pass *make_pass_analyze_swaps (gcc::context*);
> >>>>>>
> >>>>>> +rtl_opt_pass *make_pass_analyze_zext (gcc::context*);
> >>>>>> +
> >>>>>>  /* Hash table stuff for keeping track of TOC entries.  */
> >>>>>>
> >>>>>>  struct GTY((for_user)) toc_hash_struct
> >>>>>> diff --git a/gcc/config/rs6000/t-rs6000 b/gcc/config/rs6000/t-rs6000
> >>>>>> index f183b42ce1d..c1f61591d2f 100644
> >>>>>> --- a/gcc/config/rs6000/t-rs6000
> >>>>>> +++ b/gcc/config/rs6000/t-rs6000
> >>>>>> @@ -35,6 +35,11 @@ rs6000-p8swap.o: $(srcdir)/config/rs6000/rs6000-p8swap.cc
> >>>>>>         $(COMPILE) $<
> >>>>>>         $(POSTCOMPILE)
> >>>>>>
> >>>>>> +rs6000-zext-elim.o: $(srcdir)/config/rs6000/rs6000-zext-elim.cc
> >>>>>> +       $(COMPILE) $<
> >>>>>> +       $(POSTCOMPILE)
> >>>>>> +
> >>>>>> +
> >>>>>>  rs6000-d.o: $(srcdir)/config/rs6000/rs6000-d.cc
> >>>>>>         $(COMPILE) $<
> >>>>>>         $(POSTCOMPILE)
> >>>>>> diff --git a/gcc/explow.cc b/gcc/explow.cc
> >>>>>> index 32e9498ee07..316aa975e40 100644
> >>>>>> --- a/gcc/explow.cc
> >>>>>> +++ b/gcc/explow.cc
> >>>>>> @@ -654,7 +654,8 @@ copy_to_mode_reg (machine_mode mode, rtx x)
> >>>>>>    if (! general_operand (x, VOIDmode))
> >>>>>>      x = force_operand (x, temp);
> >>>>>>
> >>>>>> -  gcc_assert (GET_MODE (x) == mode || GET_MODE (x) == VOIDmode);
> >>>>>> +  gcc_assert (mode == DImode || GET_MODE (x) == mode
> >>>>>> +              || GET_MODE (x) == VOIDmode);
> >>>>>>    if (x != temp)
> >>>>>>      emit_move_insn (temp, x);
> >>>>>>    return temp;
> >>>>>> diff --git a/gcc/expr.cc b/gcc/expr.cc
> >>>>>> index 15be1c8db99..6162ef92b88 100644
> >>>>>> --- a/gcc/expr.cc
> >>>>>> +++ b/gcc/expr.cc
> >>>>>> @@ -4223,9 +4223,9 @@ emit_move_insn (rtx x, rtx y)
> >>>>>>    rtx y_cst = NULL_RTX;
> >>>>>>    rtx_insn *last_insn;
> >>>>>>    rtx set;
> >>>>>> -
> >>>>>>    gcc_assert (mode != BLKmode
> >>>>>> -             && (GET_MODE (y) == mode || GET_MODE (y) == VOIDmode));
> >>>>>> +             && (mode == DImode || GET_MODE (y) == mode
> >>>>>> +             || GET_MODE (y) == VOIDmode));
> >>>>>>
> >>>>>>    /* If we have a copy that looks like one of the following patterns:
> >>>>>>         (set (subreg:M1 (reg:M2 ...)) (subreg:M1 (reg:M2 ...)))
> >>>>>> diff --git a/gcc/optabs.cc b/gcc/optabs.cc
> >>>>>> index 4c641cab192..9d22fadc7ef 100644
> >>>>>> --- a/gcc/optabs.cc
> >>>>>> +++ b/gcc/optabs.cc
> >>>>>> @@ -7902,7 +7902,8 @@ maybe_legitimize_operand (enum insn_code icode, unsigned int opno,
> >>>>>>      input:
> >>>>>>        gcc_assert (mode != VOIDmode);
> >>>>>>        gcc_assert (GET_MODE (op->value) == VOIDmode
> >>>>>> -                 || GET_MODE (op->value) == mode);
> >>>>>> +                 || GET_MODE (op->value) == mode
> >>>>>> +                 || mode == DImode);
> >>>>>>        if (maybe_legitimize_operand_same_code (icode, opno, op))
> >>>>>>         return true;
> >>>>>>
> >>>>>> --
> >>>>>> 2.31.1
> >>>>>>