From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 40876 invoked by alias); 27 Oct 2015 12:50:00 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 39306 invoked by uid 89); 27 Oct 2015 12:49:58 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.6 required=5.0 tests=AWL,BAYES_00,KAM_ASCII_DIVIDERS,RP_MATCHES_RCVD,SPF_PASS autolearn=no version=3.3.2 X-HELO: mx2.suse.de Received: from mx2.suse.de (HELO mx2.suse.de) (195.135.220.15) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (CAMELLIA256-SHA encrypted) ESMTPS; Tue, 27 Oct 2015 12:49:57 +0000 Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id EF82BAC6A for ; Tue, 27 Oct 2015 12:49:56 +0000 (UTC) Date: Tue, 27 Oct 2015 12:50:00 -0000 From: Richard Biener To: gcc-patches@gcc.gnu.org Subject: [PATCH] Fix PR68067 Message-ID: User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-SW-Source: 2015-10/txt/msg02884.txt.bz2 The following patch adjusts negate_expr_p to account for the fact that we can't generally change a - (b - c) to (c - b) + a because -INF - 0 is ok while 0 - -INF not. Similarly for a - (b + c). While creating testcases I noticed that MULT_EXPR handling is bogus as well as with -INF/2 * 2 neither operand can be negated safely. I believe the division case is also still wrong but I refrained from touching it with this patch. Bootstrapped and tested on x86_64-unknown-linux-gnu. Richard. 2015-10-27 Richard Biener PR middle-end/68067 * fold-const.c (negate_expr_p): We cannot negate plus or minus if overflow is not wrapping. Likewise multiplication unless one operand is constant and not power of two. (fold_negate_expr): Adjust accordingly. * gcc.dg/torture/pr68067-1.c: New testcase. * gcc.dg/torture/pr68067-2.c: Likewise. Index: gcc/fold-const.c =================================================================== --- gcc/fold-const.c (revision 229404) +++ gcc/fold-const.c (working copy) @@ -443,7 +443,9 @@ negate_expr_p (tree t) case PLUS_EXPR: if (HONOR_SIGN_DEPENDENT_ROUNDING (element_mode (type)) - || HONOR_SIGNED_ZEROS (element_mode (type))) + || HONOR_SIGNED_ZEROS (element_mode (type)) + || (INTEGRAL_TYPE_P (type) + && ! TYPE_OVERFLOW_WRAPS (type))) return false; /* -(A + B) -> (-B) - A. */ if (negate_expr_p (TREE_OPERAND (t, 1)) @@ -457,12 +459,23 @@ negate_expr_p (tree t) /* We can't turn -(A-B) into B-A when we honor signed zeros. */ return !HONOR_SIGN_DEPENDENT_ROUNDING (element_mode (type)) && !HONOR_SIGNED_ZEROS (element_mode (type)) + && (! INTEGRAL_TYPE_P (type) + || TYPE_OVERFLOW_WRAPS (type)) && reorder_operands_p (TREE_OPERAND (t, 0), TREE_OPERAND (t, 1)); case MULT_EXPR: - if (TYPE_UNSIGNED (TREE_TYPE (t))) - break; + if (TYPE_UNSIGNED (type)) + break; + /* INT_MIN/n * n doesn't overflow while negating one operand it does + if n is a power of two. */ + if (INTEGRAL_TYPE_P (TREE_TYPE (t)) + && ! TYPE_OVERFLOW_WRAPS (TREE_TYPE (t)) + && ! ((TREE_CODE (TREE_OPERAND (t, 0)) == INTEGER_CST + && ! integer_pow2p (TREE_OPERAND (t, 0))) + || (TREE_CODE (TREE_OPERAND (t, 1)) == INTEGER_CST + && ! integer_pow2p (TREE_OPERAND (t, 1))))) + break; /* Fall through. */ Index: gcc/testsuite/gcc.dg/torture/pr68067-1.c =================================================================== --- gcc/testsuite/gcc.dg/torture/pr68067-1.c (revision 0) +++ gcc/testsuite/gcc.dg/torture/pr68067-1.c (working copy) @@ -0,0 +1,12 @@ +/* { dg-do run } */ + +int main() +{ + int a = -1; + static int b = -2147483647 - 1; + static int c = 0; + int t = a - (b - c); + if (t != 2147483647) + __builtin_abort(); + return 0; +} Index: gcc/testsuite/gcc.dg/torture/pr68067-2.c =================================================================== --- gcc/testsuite/gcc.dg/torture/pr68067-2.c (revision 0) +++ gcc/testsuite/gcc.dg/torture/pr68067-2.c (working copy) @@ -0,0 +1,13 @@ +/* { dg-do run } */ + +int main() +{ + int a = -1; + static int b = -2147483647 - 1; + static int c = 0; + int t = a - (b + c*-2); + if (t != 2147483647) + __builtin_abort(); + return 0; +} +