The issue of suboptimal code exists even for integer return value and not just
bool return value. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103784#c9
So the patch would need to take care of integer return values too.
On 16/03/23 10:50 am, Ajit Agarwal via Gcc-patches wrote:
> Hello All:
>
>
> This patch eliminates unnecessary zero extension instruction from power
> generated assembly.
> Bootstrapped and regtested on powerpc64-linux-gnu.
>
> Thanks & Regards
> Ajit
>
> 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 <aagar...@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;
>
