[Bug optimization/15112] New: optimizer generates code to write to unchanging memory

[Bug optimization/15112] New: optimizer generates code to write to unchanging memory

[p dot van-hoof at qub dot ac dot uk]

This is another incarnation of the problem where the optimizer generates code
that uses unchanging memory as a spill spot. The problem can be reproduced as
follows:

dogbert> gcc -c -O3 -funroll-loops a.c i.c
dogbert> gcc a.o i.o
dogbert> a.out
Segmentation fault

In this case the const int q is being written to. This problem occurs only in
gcc 3.4.0, not in gcc 3.3.3 or the mainline.

-- 
           Summary: optimizer generates code to write to unchanging memory
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: p dot van-hoof at qub dot ac dot uk
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15112

[Bug optimization/15112] optimizer generates code to write to unchanging memory

[p dot van-hoof at qub dot ac dot uk]

------- Additional Comments From p dot van-hoof at qub dot ac dot uk  2004-04-24 10:33 -------
Created an attachment (id=6155)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=6155&action=view)
code that triggers the bug


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15112

[Bug optimization/15112] optimizer generates code to write to unchanging memory

[ebotcazou at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ebotcazou at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15112

[Bug optimization/15112] [3.4 Regression] optimizer generates code to write to unchanging memory

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-04-24 13:45 -------
Confirmed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |wrong-code
   Last reconfirmed|0000-00-00 00:00:00         |2004-04-24 13:45:48
               date|                            |
            Summary|optimizer generates code to |[3.4 Regression] optimizer
                   |write to unchanging memory  |generates code to write to
                   |                            |unchanging memory
   Target Milestone|---                         |3.4.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15112

[Bug optimization/15112] [3.4 Regression] optimizer generates code to write to unchanging memory

[ebotcazou at gcc dot gnu dot org]

------- Additional Comments From ebotcazou at gcc dot gnu dot org  2004-04-28 14:27 -------
Investigating.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|ebotcazou at gcc dot gnu dot|
                   |org                         |
         AssignedTo|unassigned at gcc dot gnu   |ebotcazou at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15112

[Bug optimization/15112] [3.4 Regression] optimizer generates code to write to unchanging memory

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-05-02 12:37 -------
Subject: Bug 15112

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_4-branch
Changes by:	ebotcazou@gcc.gnu.org	2004-05-02 12:37:25

Modified files:
	gcc            : ChangeLog reload1.c 

Log message:
	PR optimization/15112
	* reload1.c (reload): Don't record unchanging memory locations.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=2.2326.2.428&r2=2.2326.2.429
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/reload1.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.419.4.4&r2=1.419.4.5



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15112

[Bug optimization/15112] [3.4 Regression] optimizer generates code to write to unchanging memory

[ebotcazou at gcc dot gnu dot org]

------- Additional Comments From ebotcazou at gcc dot gnu dot org  2004-05-02 12:42 -------
Fixed on 3.4 branch, see http://gcc.gnu.org/ml/gcc-patches/2004-05/msg00019.html .

I'm closing this PR and will open a new one for mainline because we could devise
more sophisticated ways to address the problem.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15112