[Bug optimization/11198] New: -O2 -frename-registers generates wrong code

[Bug optimization/11198] New: -O2 -frename-registers generates wrong code

[jhr.walter@t-online.de]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198

           Summary: -O2 -frename-registers generates wrong code
           Product: gcc
           Version: 3.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jhr.walter@t-online.de
                CC: gcc-bugs@gcc.gnu.org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu

The following program

----------
#include <iostream>

#include <boost/numeric/ublas/config.hpp>
#include <boost/numeric/ublas/vector.hpp>
#include <boost/numeric/ublas/matrix.hpp>
#include <boost/numeric/ublas/banded.hpp>
#include <boost/numeric/ublas/io.hpp>

namespace ublas = boost::numeric::ublas;

template<class M>
void initialize_matrix (M &m) {
    int size1 = m.size1 ();
    int size2 = m.size2 ();
    for (int i = 0; i < size1; ++ i)
        for (int j = std::max (i - 1, 0); j < std::min (i + 2, size2); ++ j)
            m (i, j) = i * size1 + j + 1.f;
}

int main () {
    ublas::banded_matrix<double> m1 (3, 3, 1, 1), m2 (3, 3, 1, 1);
    ublas::banded_adaptor<ublas::banded_matrix<double> > bam1 (m1, 1, 1), bam2 
(m2, 1, 1);
    initialize_matrix (bam1);
    initialize_matrix (bam2);
    bam1.swap (bam2);
    std::cout << "bam1.swap (bam2) = " << bam1 << " " << bam2 << std::endl;
}

----------

works as intended when compiled with -O2 and core dumps in swap() when 
compiled with -O2 -frename-registers like

----------
g++ -v -save-temps -I/usr/local/lib/boost_dev/boost -fabi-version=0 -DNDEBUG 
-O2 -frename-registers    bug.cpp   -o bug
Reading specs from /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3/specs
Configured with: ./configure
Thread model: posix
gcc version 3.3
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3/cc1plus -E -D__GNUG__=3 -quiet 
-v -I/usr/local/lib/boost_dev/boost -D__GNUC__=3 -D__GNUC_MINOR__=3 
-D__GNUC_PATCHLEVEL__=0 -D_GNU_SOURCE -DNDEBUG bug.cpp -fabi-version=0 
-frename-registers -O2 bug.ii
ignoring nonexistent directory "NONE/include"
ignoring nonexistent directory "/usr/local/i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/lib/boost_dev/boost
 /usr/local/include/c++/3.3
 /usr/local/include/c++/3.3/i686-pc-linux-gnu
 /usr/local/include/c++/3.3/backward
 /usr/local/include
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3/include
 /usr/include
End of search list.
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3/cc1plus -fpreprocessed bug.ii 
-quiet -dumpbase bug.cpp -auxbase bug -O2 -version -fabi-version=0 
-frename-registers -o bug.s
GNU C++ version 3.3 (i686-pc-linux-gnu)
	compiled by GNU C version 2.95.3 20010315 (SuSE).
GGC heuristics: --param ggc-min-expand=47 --param ggc-min-heapsize=31945
 as -V -Qy -o bug.o bug.s
GNU assembler version 2.11.90.0.29 (i486-suse-linux) using BFD version 
2.11.90.0.29
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3/collect2 -m elf_i386 
-dynamic-linker /lib/ld-linux.so.2 -o bug /usr/lib/crt1.o /usr/lib/crti.o 
/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3/crtbegin.o 
-L/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3 
-L/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3/../../.. bug.o -lstdc++ -lm 
-lgcc_s -lgcc -lc -lgcc_s -lgcc 
/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3/crtend.o /usr/lib/crtn.o

----------

The program work correct when compiled with -O2 -frename-registers under GCC 
3.2.1.

[Bug optimization/11198] -O2 -frename-registers generates wrong code

[jhr.walter@t-online.de]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198



------- Additional Comments From jhr.walter@t-online.de  2003-06-15 17:57 -------
Created an attachment (id=4226)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=4226&action=view)
Preprocessed source

[Bug optimization/11198] -O2 -frename-registers generates wrong code

[pinskia at physics dot uc dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198


pinskia at physics dot uc dot edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING


------- Additional Comments From pinskia at physics dot uc dot edu  2003-06-18 17:17 -------
This is very hard to isolate is there any way you could make a smaller example?

[Bug optimization/11198] -O2 -frename-registers generates wrong code

[jhr dot walter at t-online dot de]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198



------- Additional Comments From jhr dot walter at t-online dot de  2003-06-23 21:39 -------
Subject: Re:  -O2 -frename-registers generates wrong code

Hi Andrew,

I've just tried to reduce the test case for that bug once again (eliminating
some std:: dependencies), but failed. It would be great, if someone (means
you ;-) could give me some advice on how to advance.

Thanks,
Joerg

----- Original Message -----
From: "pinskia at physics dot uc dot edu" <gcc-bugzilla@gcc.gnu.org>
To: <jhr.walter@t-online.de>
Sent: Wednesday, June 18, 2003 7:17 PM
Subject: [Bug optimization/11198] -O2 -frename-registers generates wrong
code


> PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198
>
>
> pinskia at physics dot uc dot edu changed:
>
>            What    |Removed                     |Added
> --------------------------------------------------------------------------
--
>              Status|UNCONFIRMED                 |WAITING
>
>
> ------- Additional Comments From pinskia at physics dot uc dot edu
2003-06-18 17:17 -------
> This is very hard to isolate is there any way you could make a smaller
example?
>
>
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.

[Bug optimization/11198] -O2 -frename-registers generates wrong code

[pinskia at physics dot uc dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198


pinskia at physics dot uc dot edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2003-06-28 19:44:44
               date|                            |


------- Additional Comments From pinskia at physics dot uc dot edu  2003-06-28 19:44 -------
No one has figuared out how to reduce this but it still is a bug.

[Bug optimization/11198] [3.3/3.4? regression] -O2 -frename-registers generates wrong code

[giovannibajo at libero dot it]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198


giovannibajo at libero dot it changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |critical
           Keywords|                            |wrong-code
           Priority|P2                          |P1
            Summary|-O2 -frename-registers      |[3.3/3.4? regression] -O2 -
                   |generates wrong code        |frename-registers generates
                   |                            |wrong code

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[reichelt at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198


reichelt at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[3.3/3.4? regression] -O2 - |[3.3 regression] -O2 -
                   |frename-registers generates |frename-registers generates
                   |wrong code                  |wrong code


------- Additional Comments From reichelt at gcc dot gnu dot org  2003-07-03 20:46 -------
Reducing this stuff from ~34500 line to roughly 400 was quite a nightmare.
Alas, I'm stuck now: If I try to further simplify the code (e.g. by removing
unused template parameters) the bug vanishes.

I'm afraid somebody has to debug this stuff to find the bug in gcc.

The good news is, the bug doesn't seem to show up in mainline or releases
before gcc 3.3.

Regards,
Volker

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[reichelt at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198



------- Additional Comments From reichelt at gcc dot gnu dot org  2003-07-03 23:04 -------
It looks as if the problem appeared with Eric's patch

http://gcc.gnu.org/ml/gcc-cvs/2003-03/msg00627.html

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[pinskia at physics dot uc dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198



------- Additional Comments From pinskia at physics dot uc dot edu  2003-07-04 01:18 -------
If it was Eric's patch, then this is a binutils bug because the asm looks the same between the two 
versions (except for use of different registers), note this is still present in the latest cvs version of 
binutils:
GNU assembler version 2.14.90 (i686-pc-linux-gnu) using BFD version 2.14.90 20030703.

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[pinskia at physics dot uc dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198



------- Additional Comments From pinskia at physics dot uc dot edu  2003-07-04 02:23 -------
Good asm:
	pushl	%ebp
	movl	%esp, %ebp
	subl	$56, %esp
	movl	$0, -16(%ebp)
	movl	8(%ebp), %eax
	movl	12(%ebp), %edx
	movl	$0, -52(%ebp)
	movl	(%eax), %ecx
	movl	%eax, -24(%ebp)
	movl	-32(%ebp), %eax
	movl	%ecx, -20(%ebp)
	movl	$0, -32(%ebp)
	movl	%eax, -12(%ebp)
	movl	(%edx), %eax
	movl	%ecx, -40(%ebp)
	movl	%edx, -40(%ebp)
	movl	%eax, -36(%ebp)
	movl	%eax, -56(%ebp)
	movl	-48(%ebp), %eax
	movl	%eax, -28(%ebp)
	xorl	%eax, %eax
	cmpl	(%ecx), %eax; dies here in bad, ecx = -40(%ebp)

Bad:

	pushl	%ebp
	movl	%esp, %ebp
	subl	$56, %esp
	movl	$0, -16(%ebp)
	movl	8(%ebp), %eax
	movl	12(%ebp), %edx
	movl	$0, -52(%ebp)
	movl	(%eax), %ecx
	movl	%eax, -24(%ebp)
	movl	-32(%ebp), %eax
	movl	%edx, -40(%ebp)
	movl	%ecx, -20(%ebp)
	movl	%eax, -12(%ebp)
	movl	(%edx), %eax
	movl	-48(%ebp), %edx
	movl	$0, -32(%ebp)
	movl	%eax, -36(%ebp)
	movl	%edx, -28(%ebp)
	xorl	%edx, %edx
	cmpl	(%ecx), %edx ; dies here, ecx =  -20(%ebp), not the -40(%ebp) where the good 
one is.

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[ebotcazou at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198



------- Additional Comments From ebotcazou at gcc dot gnu dot org  2003-07-04 08:02 -------
Not quite. Don't forget that the AT&T style uses 'mov src,dest'.

According to GDB, the problem is rather here:
0x08048458      29            if (j < size2_ && i-j < 2)

 804844f:       dd 00                   fldl   (%eax)
 8048451:       8b 4d d8                mov    0xffffffd8(%ebp),%ecx
 8048454:       8b 11                   mov    (%ecx),%edx
 8048456:       31 c9                   xor    %ecx,%ecx
 8048458:       3b 0a                   cmp    (%edx),%ecx

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[ebotcazou at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198



------- Additional Comments From ebotcazou at gcc dot gnu dot org  2003-07-04 09:20 -------
Here's the code at stake (from the buggy version, but functionally identical to
the correct version):

.L17:
	fldl	(%eax)
	movl	-40(%ebp), %ecx
	movl	(%ecx), %edx
	xorl	%ecx, %ecx
	cmpl	(%edx), %ecx

The problem is the contents of -40(%ebp).

In the correct version, -40(%ebp) is written twice in a row

	movl	(%edx), %eax
	movl	%ecx, -40(%ebp)
	movl	%edx, -40(%ebp)
	movl	%eax, -36(%ebp)

In the buggy version, -40(%ebp) is written twice too, but in the reverse order

	movl	%edx, -40(%ebp)
	movl	%ecx, -20(%ebp)
	movl	%eax, -12(%ebp)
	movl	(%edx), %eax
	movl	-48(%ebp), %edx
	movl	$0, -32(%ebp)
	movl	%eax, -36(%ebp)
	movl	%edx, -28(%ebp)
	xorl	%edx, %edx
	cmpl	(%ecx), %edx
	movl	%ecx, -40(%ebp)

The 2nd scheduling pass swaps the two sets, because the memory locations are not
marked as aliasing:

(insn:HI 27 21 40 0 0x4020fc08 (set (mem/s:SI (plus:SI (reg/f:SI 6 ebp)
                (const_int -40 [0xffffffd8])) [7 <variable>.dead1+0 S4 A32])
        (reg/v/f:SI 2 ecx [64])) 38 {*movsi_1} (insn_list 21 (nil))
    (nil))

(insn:HI 83 73 87 0 0x4020fd10 (set (mem/s:SI (plus:SI (reg/f:SI 6 ebp)
                (const_int -40 [0xffffffd8])) [5 <variable>.a+0 S4 A32])
        (reg/v/u/f:SI 1 edx [59])) 38 {*movsi_1} (nil)
    (expr_list:REG_DEAD (reg/v/u/f:SI 1 edx [59])
        (nil)))

If I understand correctly the code, the variable 'dead1' comes from the first
iterator it1, while the variable 'a' comes from the second iterator it2. For
some reason, they are wrongly given the same stack slot.

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[schwab at suse dot de]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198


schwab at suse dot de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |schwab at suse dot de


------- Additional Comments From schwab at suse dot de  2003-07-04 09:38 -------
Could this be the same as bug 11320?

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[reichelt at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198


reichelt at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4                         |3.3.1

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[ebotcazou at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198



------- Additional Comments From ebotcazou at gcc dot gnu dot org  2003-07-04 13:12 -------
If bug 11320 is indeed a reload bug, no.

The problem pertains to aliasing here: the slot assigned to the temporary

   matrix<>::iterator1(bam1.m)

is reused for

   adaptor<>::a_iterator1 it2

because the types conflict according to objects_must_conflict_p. The reasoning
is probably that, since the types conflicts, operations on objects of these
types cannot be reordered by the scheduling passes later.

The problem is that at least one member of the first type (dead1) doesn't
conflict with at least one member of the second type (a), so the scheduling pass
swaps insn 27 and insn 83.

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[ebotcazou at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198


ebotcazou at gcc dot gnu dot org changed:

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

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[cvs-commit at gcc dot gnu dot org]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198



------- Additional Comments From cvs-commit at gcc dot gnu dot org  2003-07-07 07:25 -------
Subject: Bug 11198

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	ebotcazou@gcc.gnu.org	2003-07-07 07:25:36

Modified files:
	gcc            : ChangeLog alias.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/g++.dg/opt: stack1.C 

Log message:
	PR optimization/11198
	* alias.c (objects_must_conflict_p): Return 1 if the types have
	the same alias set, not if the alias sets only conflict.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.372&r2=2.373
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/alias.c.diff?cvsroot=gcc&r1=1.195&r2=1.196
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.2845&r2=1.2846
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/opt/stack1.C.diff?cvsroot=gcc&r1=NONE&r2=1.1

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[cvs-commit at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198



------- Additional Comments From cvs-commit at gcc dot gnu dot org  2003-07-07 07:31 -------
Subject: Bug 11198

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_3-branch
Changes by:	ebotcazou@gcc.gnu.org	2003-07-07 07:31:48

Modified files:
	gcc            : ChangeLog alias.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/g++.dg/opt: stack1.C 

Log message:
	PR optimization/11198
	* alias.c (objects_must_conflict_p): Return 1 if the types have
	the same alias set, not if the alias sets only conflict.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.16114.2.636&r2=1.16114.2.637
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/alias.c.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.181.2.1&r2=1.181.2.2
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.2261.2.220&r2=1.2261.2.221
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/opt/stack1.C.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=NONE&r2=1.1.2.1

[Bug optimization/11198] [3.3 regression] -O2 -frename-registers generates wrong code

[ebotcazou at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11198


ebotcazou at gcc dot gnu dot org changed:

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


------- Additional Comments From ebotcazou at gcc dot gnu dot org  2003-07-07 07:37 -------
See http://gcc.gnu.org/ml/gcc-patches/2003-07/msg00564.html