From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-333863-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 26295 invoked by alias); 15 Oct 2010 00:53:26 -0000
Received: (qmail 26286 invoked by uid 22791); 15 Oct 2010 00:53:25 -0000
X-SWARE-Spam-Status: No, hits=-2.4 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00,MISSING_MID
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; Fri, 15 Oct 2010 00:53:21 +0000
From: "zsojka at seznam dot cz" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/46029] -ftree-loop-if-convert-stores causes FAIL: libstdc++-v3/testsuite/ext/pb_ds/example/tree_intervals.cc
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: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: zsojka at seznam dot cz
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Changed-Fields:
In-Reply-To: <bug-46029-4@http.gcc.gnu.org/bugzilla/>
References: <bug-46029-4@http.gcc.gnu.org/bugzilla/>
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Date: Fri, 15 Oct 2010 00:53:00 -0000
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2010-10/txt/msg01252.txt.bz2
Message-ID: <20101015005300.ev3i-RrO2idlxTptM5YbyXPIChctxpV3Kiriy6DUBzU@z>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46029

--- Comment #1 from Zdenek Sojka <zsojka at seznam dot cz> 2010-10-15 00:53:15 UTC ---
Created attachment 22048
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22048
hopefully reduced testcase

$ g++ -O -ftree-loop-if-convert-stores pr46029.C
$ ./a.out 
Segmentation fault

In the assembly, with -ftree-loop-if-convert-stores, "nd_it.get_l_child
().get_metadata ()" in apply_update() is loaded unconditionally.

62a64
>       mov     esi, 0  # tmp69,
64,69c66,70
<       mov     rcx, QWORD PTR [rax]    # D.2294, p_nd_32->m_p_left
<       mov     edx, 0  # l_max_endpoint,
<       test    rcx, rcx        # D.2294
<       je      .L3     #,
<       mov     edx, DWORD PTR [rcx+16] # l_max_endpoint, MEM[(unsigned int
&)D.2294_12 + 16]
< .L3:
---
>       mov     rdx, QWORD PTR [rax]    # D.2294, p_nd_32->m_p_left
>       mov     ecx, DWORD PTR [rdx+16] # l_max_endpoint, MEM[(unsigned int &)D.2294_12 + 16]
>       test    rdx, rdx        # D.2294
>       mov     edx, esi        # l_max_endpoint, tmp69
>       cmovne  edx, ecx        # l_max_endpoint,, l_max_endpoint

In the first case, memory is not accessed if the pointer is NULL, but in the
second, "mov ecx, DWORD PTR [rdx+16]" reads invalid memory.