From patchwork Mon Oct 18 13:37:57 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiufu Guo X-Patchwork-Id: 46347 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 081983858402 for ; Mon, 18 Oct 2021 13:38:38 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 081983858402 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1634564318; bh=xxVGfnFPf9+9aTZPOeNePJvsZ6bThxPc34+bunT59YE=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=bzdcHO/Y0jvHyGJH4yB15+cr9g7OLowi1TUsEEIbtxHYQQOVw0IB2voyDj4RcCyVE m8wLfxzJxYGz9VOVaoHp0yxbeVxJ9/TTg1YVzlIZitcMIqE7SvNdJe4MuGPDhQ76YT B0vs5AC7BoqPX3pi517l44N9qSxUNcM8m/nQt3Qk= X-Original-To: gcc-patches@gcc.gnu.org Delivered-To: gcc-patches@gcc.gnu.org Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by sourceware.org (Postfix) with ESMTPS id 0C3213858400 for ; Mon, 18 Oct 2021 13:38:07 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 0C3213858400 Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 19ICMok2000582; Mon, 18 Oct 2021 09:38:06 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3bs8vkst6c-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 18 Oct 2021 09:38:06 -0400 Received: from m0098410.ppops.net (m0098410.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 19ICNHXw001181; Mon, 18 Oct 2021 09:38:05 -0400 Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 3bs8vkst4s-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 18 Oct 2021 09:38:05 -0400 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 19IDbkI2023157; Mon, 18 Oct 2021 13:38:03 GMT Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by ppma03ams.nl.ibm.com with ESMTP id 3bqpc9f4up-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 18 Oct 2021 13:38:03 +0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 19IDbxqn48562650 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 18 Oct 2021 13:37:59 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F0CFF11C052; Mon, 18 Oct 2021 13:37:58 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D6C1C11C05E; Mon, 18 Oct 2021 13:37:57 +0000 (GMT) Received: from pike.rch.stglabs.ibm.com (unknown [9.5.12.127]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 18 Oct 2021 13:37:57 +0000 (GMT) To: gcc-patches@gcc.gnu.org Subject: [RFC] Overflow check in simplifying exit cond comparing two IVs. Date: Mon, 18 Oct 2021 21:37:57 +0800 Message-Id: <20211018133757.3960-1-guojiufu@linux.ibm.com> X-Mailer: git-send-email 2.17.1 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: _LKC43gm7PNCzYdkdwcifEv3wGvilMNP X-Proofpoint-ORIG-GUID: CWK7WfiQosemhnKvEQ-71E6T05q0MAz2 X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.0.607.475 definitions=2021-10-18_05,2021-10-14_02,2020-04-07_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 mlxlogscore=999 bulkscore=0 clxscore=1011 suspectscore=0 adultscore=0 phishscore=0 mlxscore=0 spamscore=0 lowpriorityscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109230001 definitions=main-2110180084 X-Spam-Status: No, score=-12.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Jiufu Guo via Gcc-patches From: Jiufu Guo Reply-To: Jiufu Guo Cc: rguenther@suse.de, segher@kernel.crashing.org, wschmidt@linux.ibm.com, jlaw@tachyum.com, dje.gcc@gmail.com Errors-To: gcc-patches-bounces+patchwork=sourceware.org@gcc.gnu.org Sender: "Gcc-patches" With reference the discussions in: https://gcc.gnu.org/pipermail/gcc-patches/2021-July/574334.html https://gcc.gnu.org/pipermail/gcc-patches/2021-June/572006.html https://gcc.gnu.org/pipermail/gcc-patches/2021-September/578672.html Base on the patches in above discussion, we may draft a patch to fix the issue. In this patch, to make sure it is ok to change '{b0,s0} op {b1,s1}' to '{b0,s0-s1} op {b1,0}', we also compute the condition which could assume both 2 ivs are not overflow/wrap: the niter "of '{b0,s0-s1} op {b1,0}'" < the niter "of untill wrap for iv0 or iv1". Does this patch make sense? BR, Jiufu Guo gcc/ChangeLog: PR tree-optimization/100740 * tree-ssa-loop-niter.c (number_of_iterations_cond): Add assume condition for combining of two IVs gcc/testsuite/ChangeLog: * gcc.c-torture/execute/pr100740.c: New test. --- gcc/tree-ssa-loop-niter.c | 103 +++++++++++++++--- .../gcc.c-torture/execute/pr100740.c | 11 ++ 2 files changed, 99 insertions(+), 15 deletions(-) create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr100740.c diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c index 75109407124..f2987a4448d 100644 --- a/gcc/tree-ssa-loop-niter.c +++ b/gcc/tree-ssa-loop-niter.c @@ -1863,29 +1863,102 @@ number_of_iterations_cond (class loop *loop, provided that either below condition is satisfied: - a) the test is NE_EXPR; - b) iv0.step - iv1.step is integer and iv0/iv1 don't overflow. + a) iv0.step - iv1.step is integer and iv0/iv1 don't overflow. + b) assumptions in below table also need to be satisfied. + + | iv0 | iv1 | assum (iv0step > iv1->step; + The second three rows: iv0->step < iv1->step. This rarely occurs in practice, but it is simple enough to manage. */ if (!integer_zerop (iv0->step) && !integer_zerop (iv1->step)) { + if (TREE_CODE (iv0->step) != INTEGER_CST + || TREE_CODE (iv1->step) != INTEGER_CST) + return false; + if (!iv0->no_overflow || !iv1->no_overflow) + return false; + tree step_type = POINTER_TYPE_P (type) ? sizetype : type; - tree step = fold_binary_to_constant (MINUS_EXPR, step_type, - iv0->step, iv1->step); - - /* No need to check sign of the new step since below code takes care - of this well. */ - if (code != NE_EXPR - && (TREE_CODE (step) != INTEGER_CST - || !iv0->no_overflow || !iv1->no_overflow)) + tree step + = fold_binary_to_constant (MINUS_EXPR, step_type, iv0->step, iv1->step); + + if (code != NE_EXPR && tree_int_cst_sign_bit (step)) return false; - iv0->step = step; - if (!POINTER_TYPE_P (type)) - iv0->no_overflow = false; + bool positive0 = !tree_int_cst_sign_bit (iv0->step); + bool positive1 = !tree_int_cst_sign_bit (iv1->step); - iv1->step = build_int_cst (step_type, 0); - iv1->no_overflow = true; + /* Cases in rows 2 and 4 of above table. */ + if ((positive0 && !positive1) || (!positive0 && positive1)) + { + iv0->step = step; + iv1->step = build_int_cst (step_type, 0); + return number_of_iterations_cond (loop, type, iv0, code, iv1, + niter, only_exit, every_iteration); + } + + affine_iv i_0, i_1; + class tree_niter_desc num; + i_0 = *iv0; + i_1 = *iv1; + i_0.step = step; + i_1.step = build_int_cst (step_type, 0); + if (!number_of_iterations_cond (loop, type, &i_0, code, &i_1, &num, + only_exit, every_iteration)) + return false; + + affine_iv i0, i1; + class tree_niter_desc num_wrap; + i0 = *iv0; + i1 = *iv1; + + /* Reset iv0 and iv1 to calculate the niter which cause overflow. */ + if (tree_int_cst_lt (i1.step, i0.step)) + { + if (positive0 && positive1) + i0.step = build_int_cst (step_type, 0); + else if (!positive0 && !positive1) + i1.step = build_int_cst (step_type, 0); + if (code == NE_EXPR) + code = LT_EXPR; + } + else + { + if (positive0 && positive1) + i1.step = build_int_cst (step_type, 0); + else if (!positive0 && !positive1) + i0.step = build_int_cst (step_type, 0); + gcc_assert (code == NE_EXPR); + code = GT_EXPR; + } + + /* Calculate the niter which cause overflow. */ + if (!number_of_iterations_cond (loop, type, &i0, code, &i1, &num_wrap, + only_exit, every_iteration)) + return false; + + /* Make assumption there is no overflow. */ + tree assum + = fold_build2 (LE_EXPR, boolean_type_node, num.niter, + fold_convert (TREE_TYPE (num.niter), num_wrap.niter)); + num.assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, + num.assumptions, assum); + + *iv0 = i_0; + *iv1 = i_1; + *niter = num; + return true; } /* If the result of the comparison is a constant, the loop is weird. More diff --git a/gcc/testsuite/gcc.c-torture/execute/pr100740.c b/gcc/testsuite/gcc.c-torture/execute/pr100740.c new file mode 100644 index 00000000000..8fcdaffef3b --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/execute/pr100740.c @@ -0,0 +1,11 @@ +/* PR tree-optimization/100740 */ + +unsigned a, b; +int main() { + unsigned c = 0; + for (a = 0; a < 2; a++) + for (b = 0; b < 2; b++) + if (++c < a) + __builtin_abort (); + return 0; +}