On Mon, 6 Jul 2026, Tamar Christina wrote:
> This commits adds gimple-isel-match.pd which is a match.pd version that only
> applies it's rewriting rules at gimple-isel time. The normal match.pd rules
> are also later applied.
>
> The file is currently empty, but I have some patches to add vector comparisons
> matching to this and I noticed a few cases already in isel that can be
> simplified using the match.pd machinery.
>
> Bootstrapped Regtested on aarch64-none-linux-gnu,
> arm-none-linux-gnueabihf, x86_64-pc-linux-gnu
> -m32, -m64 and no issues.
>
> Ok for master?
>
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
> * Makefile.in: Add entries for gimple-isel-match.pd
> * gimple-isel.cc (gimple_isel_simplify): Forward declare.
> (gimple_isel_match_stmt): New.
> (pass_gimple_isel::execute): Call it.
> * gimple-isel-match.pd: New file.
>
> ---
> diff --git a/gcc/Makefile.in b/gcc/Makefile.in
> index
> 536e2faaaf882d412bdb5bba649f184e672f2be5..f13972b9a5a01efefa5ae98d1eaab7138bf2c9f2
> 100644
> --- a/gcc/Makefile.in
> +++ b/gcc/Makefile.in
> @@ -228,6 +228,10 @@ GIMPLE_MATCH_PD_SEQ_O = $(patsubst %, gimple-match-%.o,
> $(MATCH_SPLITS_SEQ))
> GENERIC_MATCH_PD_SEQ_SRC = $(patsubst %, generic-match-%.cc,
> $(MATCH_SPLITS_SEQ))
> GENERIC_MATCH_PD_SEQ_O = $(patsubst %, generic-match-%.o,
> $(MATCH_SPLITS_SEQ))
>
> +# The number of splits to be made for the gimple-isel-match.pd files.
> +GIMPLE_ISEL_MATCH_PD_SEQ_SRC = $(patsubst %, gimple-isel-match-%.cc,
> $(MATCH_SPLITS_SEQ))
> +GIMPLE_ISEL_MATCH_PD_SEQ_O = $(patsubst %, gimple-isel-match-%.o,
> $(MATCH_SPLITS_SEQ))
> +
> # The number of splits to be made for the insn-emit files.
> NUM_INSNEMIT_SPLITS = @DEFAULT_INSNEMIT_PARTITIONS@
> INSNEMIT_SPLITS_SEQ = $(wordlist 1,$(NUM_INSNEMIT_SPLITS),$(one_to_9999))
> @@ -1401,6 +1405,7 @@ ANALYZER_OBJS = \
> # the last objects to finish building.
> OBJS = \
> $(GIMPLE_MATCH_PD_SEQ_O) \
> + $(GIMPLE_ISEL_MATCH_PD_SEQ_O) \
> gimple-match-exports.o \
> $(GENERIC_MATCH_PD_SEQ_O) \
> insn-attrtab.o \
> @@ -1988,7 +1993,8 @@ MOSTLYCLEANFILES = insn-flags.h insn-config.h
> insn-codes.h \
> insn-attr.h insn-attr-common.h insn-attrtab.cc insn-dfatab.cc \
> insn-latencytab.cc insn-opinit.cc insn-opinit.h insn-preds.cc
> insn-constants.h \
> tm-preds.h tm-constrs.h checksum-options $(GIMPLE_MATCH_PD_SEQ_SRC) \
> - $(GENERIC_MATCH_PD_SEQ_SRC) gimple-match-auto.h generic-match-auto.h \
> + $(GIMPLE_ISEL_MATCH_PD_SEQ_SRC) $(GENERIC_MATCH_PD_SEQ_SRC) \
> + gimple-match-auto.h generic-match-auto.h \
> tree-check.h min-insn-modes.cc insn-modes.cc insn-modes.h
> insn-modes-inline.h \
> genrtl.h gt-*.h gtype-*.h gtype-desc.cc gtyp-input.list \
> case-cfn-macros.h cfn-operators.pd \
> @@ -2763,6 +2769,7 @@ $(common_out_object_file): $(common_out_file)
> insn-extract.cc insn-output.cc \
> insn-peep.cc insn-attr.h insn-attr-common.h insn-attrtab.cc \
> insn-dfatab.cc insn-latencytab.cc insn-preds.cc \
> + $(GIMPLE_ISEL_MATCH_PD_SEQ_SRC) \
> $(GIMPLE_MATCH_PD_SEQ_SRC) $(GENERIC_MATCH_PD_SEQ_SRC) \
> gimple-match-auto.h generic-match-auto.h insn-target-def.h
>
> @@ -3078,6 +3085,23 @@ s-generic-match: build/genmatch$(build_exeext) \
> generic-match-auto.h
> $(STAMP) s-generic-match
>
> +# Add gimple-isel-match.pd
> +$(GIMPLE_ISEL_MATCH_PD_SEQ_SRC): s-gimple-isel-match gimple-match-head.cc;
> @true
> +gimple-isel-match-auto.h: s-gimple-isel-match; @true
> +
> +s-gimple-isel-match: build/genmatch$(build_exeext) \
> + $(srcdir)/gimple-isel-match.pd cfn-operators.pd
> + $(RUN_GEN) build/genmatch$(build_exeext) --gimple \
> + --header=tmp-gimple-isel-match-auto.h \
> + --include=gimple-isel-match-auto.h --namespace=isel \
> + $(srcdir)/gimple-isel-match.pd $(patsubst %, tmp-%,
> $(GIMPLE_ISEL_MATCH_PD_SEQ_SRC))
> + $(foreach id, $(MATCH_SPLITS_SEQ), \
> + $(SHELL) $(srcdir)/../move-if-change tmp-gimple-isel-match-$(id).cc \
> + gimple-isel-match-$(id).cc;)
> + $(SHELL) $(srcdir)/../move-if-change tmp-gimple-isel-match-auto.h \
> + gimple-isel-match-auto.h
> + $(STAMP) s-gimple-isel-match
> +
> GTFILES = $(CPPLIB_H) $(srcdir)/input.h $(srcdir)/coretypes.h \
> $(host_xm_file_list) \
> $(OPTIONS_H_EXTRA) \
> @@ -3217,6 +3241,7 @@ generated_files = config.h tm.h $(TM_P_H) $(TM_D_H)
> $(TM_JIT_H) $(TM_H) \
> $(ALL_GTFILES_H) gtype-desc.cc gtype-desc.h version.h \
> options.h target-hooks-def.h insn-opinit.h \
> common/common-target-hooks-def.h pass-instances.def \
> + $(GIMPLE_ISEL_MATCH_PD_SEQ_SRC) \
> $(GIMPLE_MATCH_PD_SEQ_SRC) $(GENERIC_MATCH_PD_SEQ_SRC) \
> gimple-match-auto.h generic-match-auto.h \
> c-family/c-target-hooks-def.h d/d-target-hooks-def.h \
> diff --git a/gcc/gimple-isel-match.pd b/gcc/gimple-isel-match.pd
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..9e2a2044ba5866389067cfff529b064d1885ea36
> --- /dev/null
> +++ b/gcc/gimple-isel-match.pd
> @@ -0,0 +1,46 @@
> +/* Match-and-simplify patterns for GIMPLE folding during instruction
> selection.
> + This file is consumed by genmatch which produces gimple-isel-match.cc.
> +
> + Copyright (C) 2026 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/>. */
> +
> +
> +/* Generic tree predicates we inherit. */
> +(define_predicates
> + integer_onep integer_zerop integer_all_onesp integer_minus_onep
> + integer_each_onep integer_truep integer_nonzerop
> + real_zerop real_onep real_minus_onep
> + zerop
> + initializer_each_zero_or_onep
> + CONSTANT_CLASS_P
> + poly_int_tree_p
> + tree_expr_nonnegative_p
> + tree_expr_nonzero_p
> + integer_valued_real_p
> + integer_pow2p
> + uniform_integer_cst_p
> + HONOR_NANS
> + uniform_vector_p
> + expand_vec_cmp_expr_p
> + bitmask_inv_cst_vector_p)
> +
> +/* Operator lists. */
> +(define_operator_list tcc_comparison
> + lt le eq ne ge gt unordered ordered unlt unle ungt unge uneq
> ltgt)
> +
> +#include "cfn-operators.pd"
> diff --git a/gcc/gimple-isel.cc b/gcc/gimple-isel.cc
> index
> b193e27b183e1a83d73369b629c81ea0d7db43cd..b834c05d65eab82b06e6b0be00b73d50384a734e
> 100644
> --- a/gcc/gimple-isel.cc
> +++ b/gcc/gimple-isel.cc
> @@ -40,6 +40,39 @@ along with GCC; see the file COPYING3. If not see
> #include "gimple-fold.h"
> #include "internal-fn.h"
> #include "fold-const.h"
> +#include "gimple-match.h"
> +
> +extern bool gimple_isel_simplify (gimple_match_op *, gimple_seq *,
> + tree (*) (tree));
> +
> +/* Try to apply the instruction-selection-specific match.pd rules to *GSI.
> */
> +
> +static bool
> +gimple_isel_match_stmt (gimple_stmt_iterator *gsi)
> +{
So that's basically fold_stmt (), right? Why not provide an
overload for that specifying the simplifier?
Did you consider a gimple_match_op::set_simplifier () and tracking
the simplifier there?
> + gimple *stmt = gsi_stmt (*gsi);
> + if (!gimple_has_lhs (stmt))
> + return false;
> +
> + gimple_seq seq = NULL;
> + gimple_match_op res_op;
> + if (!gimple_simplify (stmt, &res_op, &seq, NULL, NULL,
> + gimple_isel_simplify))
> + {
> + gimple_seq_discard (seq);
> + return false;
> + }
> +
> + tree lhs = gimple_get_lhs (stmt);
> + if (!maybe_push_res_to_seq (&res_op, &seq, lhs))
> + {
> + gimple_seq_discard (seq);
> + return false;
> + }
> +
> + gsi_replace_with_seq_vops (gsi, seq);
> + return true;
> +}
>
> /* Expand all ARRAY_REF(VIEW_CONVERT_EXPR) gimple assignments into calls to
> internal function based on vector type of selected expansion.
> @@ -1360,6 +1393,9 @@ pass_gimple_isel::execute (struct function *fun)
> /* Give the target first try at replacing the instruction. */
> cfg_changed |= targetm.instruction_selection (fun, &gsi);
>
> + /* Apply gimple-isel-match.pd patterns. */
> + gimple_isel_match_stmt (&gsi);
> +
> /* Pre-expand VEC_COND_EXPRs to .VCOND* internal function
> calls mapping to supported optabs. */
> gimple *g = gimple_expand_vec_cond_expr (&gsi);
> @@ -1400,4 +1436,3 @@ make_pass_gimple_isel (gcc::context *ctxt)
> {
> return new pass_gimple_isel (ctxt);
> }
> -
>
>
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Jochen Jaser, Andrew McDonald; (HRB 36809, AG Nuernberg)
