From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by sourceware.org (Postfix) with ESMTP id B32753858D32 for ; Sun, 17 Sep 2023 15:29:06 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org B32753858D32 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A95911FB; Sun, 17 Sep 2023 08:29:43 -0700 (PDT) Received: from localhost (e121540-lin.manchester.arm.com [10.32.110.72]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CF4793F67D; Sun, 17 Sep 2023 08:29:05 -0700 (PDT) From: Richard Sandiford To: Juzhe-Zhong Mail-Followup-To: Juzhe-Zhong ,gcc-patches@gcc.gnu.org, rguenther@suse.de, richard.sandiford@arm.com Cc: gcc-patches@gcc.gnu.org, rguenther@suse.de Subject: Re: [PATCH V2] internal-fn: Support undefined rtx for uninitialized SSA_NAME References: <20230917144749.1032038-1-juzhe.zhong@rivai.ai> Date: Sun, 17 Sep 2023 16:29:04 +0100 In-Reply-To: <20230917144749.1032038-1-juzhe.zhong@rivai.ai> (Juzhe-Zhong's message of "Sun, 17 Sep 2023 22:47:49 +0800") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Spam-Status: No, score=-24.8 required=5.0 tests=BAYES_00,GIT_PATCH_0,KAM_DMARC_NONE,KAM_DMARC_STATUS,KAM_LAZY_DOMAIN_SECURITY,KAM_SHORT,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Juzhe-Zhong writes: > According to PR: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110751 > > As Richard and Richi suggested, we recognize uninitialized SSA_NAME and convert it > into SCRATCH rtx if the target predicate allows SCRATCH. > > It can help to reduce redundant data move instructions of targets like RISC-V. > > gcc/ChangeLog: > > * internal-fn.cc (expand_fn_using_insn): Support undefined rtx. > * optabs.cc (maybe_legitimize_operand): Ditto. > (can_reuse_operands_p): Ditto. > * optabs.h (enum expand_operand_type): Ditto. > (create_undefined_input_operand): Ditto. > > --- > gcc/internal-fn.cc | 4 ++++ > gcc/optabs.cc | 16 ++++++++++++++++ > gcc/optabs.h | 14 +++++++++++++- > 3 files changed, 33 insertions(+), 1 deletion(-) > > diff --git a/gcc/internal-fn.cc b/gcc/internal-fn.cc > index 0fd34359247..61d5a9e4772 100644 > --- a/gcc/internal-fn.cc > +++ b/gcc/internal-fn.cc > @@ -247,6 +247,10 @@ expand_fn_using_insn (gcall *stmt, insn_code icode, unsigned int noutputs, > create_convert_operand_from (&ops[opno], rhs_rtx, > TYPE_MODE (rhs_type), > TYPE_UNSIGNED (rhs_type)); > + else if (TREE_CODE (rhs) == SSA_NAME > + && SSA_NAME_IS_DEFAULT_DEF (rhs) > + && VAR_P (SSA_NAME_VAR (rhs))) > + create_undefined_input_operand (&ops[opno], TYPE_MODE (rhs_type)); > else > create_input_operand (&ops[opno], rhs_rtx, TYPE_MODE (rhs_type)); > opno += 1; > diff --git a/gcc/optabs.cc b/gcc/optabs.cc > index 32ff379ffc3..d8c771547a3 100644 > --- a/gcc/optabs.cc > +++ b/gcc/optabs.cc > @@ -8102,6 +8102,21 @@ maybe_legitimize_operand (enum insn_code icode, unsigned int opno, > goto input; > } > break; > + > + case EXPAND_UNDEFINED: > + { > + mode = insn_data[(int) icode].operand[opno].mode; > + rtx scratch = gen_rtx_SCRATCH (mode); A scratch of the right mode should already be available in op->value, since it was created by create_undefined_input_operand. If that doesn't work for some reason, then it would be better for create_undefined_input_operand to pass NULL_RTX as the "value" argument to create_expand_operand. > + /* For SCRATCH rtx which is converted from uninitialized > + SSA, we convert it as fresh pseudo when target doesn't > + allow scratch rtx in predicate. Otherwise, return true. */ > + if (!insn_operand_matches (icode, opno, scratch)) > + { > + op->value = gen_reg_rtx (mode); The mode should come from op->mode. > + goto input; > + } > + return true; > + } > } > return insn_operand_matches (icode, opno, op->value); > } > @@ -8147,6 +8162,7 @@ can_reuse_operands_p (enum insn_code icode, > case EXPAND_INPUT: > case EXPAND_ADDRESS: > case EXPAND_INTEGER: > + case EXPAND_UNDEFINED: > return true; I think this should be in the "return false" block instead. > > case EXPAND_CONVERT_TO: > diff --git a/gcc/optabs.h b/gcc/optabs.h > index c80b7f4dc1b..4eb1f9ee09a 100644 > --- a/gcc/optabs.h > +++ b/gcc/optabs.h > @@ -37,7 +37,8 @@ enum expand_operand_type { > EXPAND_CONVERT_TO, > EXPAND_CONVERT_FROM, > EXPAND_ADDRESS, > - EXPAND_INTEGER > + EXPAND_INTEGER, > + EXPAND_UNDEFINED Sorry, this was my bad suggestion. I should have suggested EXPAND_UNDEFINED_INPUT, to match the name of the function. Thanks, Richard > }; > > /* Information about an operand for instruction expansion. */ > @@ -117,6 +118,17 @@ create_input_operand (class expand_operand *op, rtx value, > create_expand_operand (op, EXPAND_INPUT, value, mode, false); > } > > +/* Make OP describe an undefined input operand for uninitialized > + SSA. It's the scratch operand with mode MODE; MODE cannot be > + VOIDmode. */ > + > +inline void > +create_undefined_input_operand (class expand_operand *op, machine_mode mode) > +{ > + create_expand_operand (op, EXPAND_UNDEFINED, gen_rtx_SCRATCH (mode), mode, > + false); > +} > + > /* Like create_input_operand, except that VALUE must first be converted > to mode MODE. UNSIGNED_P says whether VALUE is unsigned. */