From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 19355 invoked by alias); 23 May 2011 16:44:04 -0000 Received: (qmail 19196 invoked by uid 22791); 23 May 2011 16:44:02 -0000 X-SWARE-Spam-Status: No, hits=-2.7 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 23 May 2011 16:43:48 +0000 From: "vries at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/49121] [4.7 Regression] FAIL: gcc.dg/tree-ssa/ivopt_infer_2.c scan-tree-dump-times ivopts "Replacing" 0 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: tree-optimization X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: vries at gcc dot gnu.org X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: vries at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.7.0 X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Date: Mon, 23 May 2011 16:44:00 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2011-05/txt/msg02089.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49121 --- Comment #3 from vries at gcc dot gnu.org 2011-05-23 16:07:04 UTC --- test case: ... #ifndef TYPE #define TYPE char* #endif extern int a[]; /* Can not infer loop iteration from array -- exit test can not be replaced. */ void foo (int i_width, TYPE dst, TYPE src1, TYPE src2) { TYPE dstn= dst + i_width; TYPE dst0 = dst; unsigned long long i = 0; for( ; dst <= dstn; ) { dst0[i] = ( src1[i] + src2[i] + 1 +a[i]) >> 1; dst++; i += 16; } } ... test case representation at ivopts: ... foo (int i_width, char * dst, char * src1, char * src2) { long long unsigned int i; char * dstn; char D.2707; int D.2706; int D.2705; int D.2704; int D.2703; int D.2702; int D.2701; char D.2700; char * D.2699; int D.2698; char D.2697; char * D.2696; char * D.2695; long unsigned int D.2694; : D.2694_4 = (long unsigned int) i_width_3(D); dstn_6 = dst_5(D) + D.2694_4; if (dst_5(D) <= dstn_6) goto ; else goto ; : : # dst_32 = PHI # i_33 = PHI D.2695_9 = dst_5(D) + i_33; D.2696_11 = src1_10(D) + i_33; D.2697_12 = *D.2696_11; D.2698_13 = (int) D.2697_12; D.2699_15 = src2_14(D) + i_33; D.2700_16 = *D.2699_15; D.2701_17 = (int) D.2700_16; D.2702_18 = D.2698_13 + D.2701_17; D.2703_19 = D.2702_18 + 1; D.2704_20 = a[i_33]; D.2705_21 = D.2703_19 + D.2704_20; D.2706_22 = D.2705_21 >> 1; D.2707_23 = (char) D.2706_22; *D.2695_9 = D.2707_23; dst_24 = dst_32 + 1; i_25 = i_33 + 16; if (dstn_6 >= dst_24) goto ; else goto ; : goto ; : : return; } ... the patch causes estimated_loop_iterations (loop, true, &max_niter) in may_eliminate_iv to return a different value: without patch: 0x10000000000000000 with patch: 0x01000000000000000 The analysis in the patch concludes that the pointer arithmetic statement D.2695_9 = dst_5(D) + i_33 can only be executed 0x01000000000000000 times, based on the fact that i is incremented with 16 each iteration. Note that the statement corresponds to the pointer arithmetic in 'dst0[i]'. Since the proposed new char pointer iterator can represent 0x10000000000000000 distinct values, may_eliminate_iv returns true, and the exit test is replaced: ... Replacing exit test: if (dstn_6 >= dst_24) ... This causes the check: ... /* { dg-final { scan-tree-dump-times "Replacing" 0 "ivopts"} } */ ... to fail. The test case needs to be adapted.