[Bug target/23453] New: [4.0 4.1 regression] miscompilation of PARI/GP on x86

[Bug target/23453] New: [4.0 4.1 regression] miscompilation of PARI/GP on x86

[debian-gcc at lists dot debian dot org]

[forwarded from http://bugs.debian.org/309210]

rechecked with 4.0 CVS 20050816

wrong code for PARI/GP 2.2.10 on x86.
The pari source code can be found here:
<http://pari.math.u-bordeaux.fr/pub/pari/unstable/pari-2.2.10.alpha.tar.gz>

The problem is in the file src/basemath/alglin1.c, function ker0().

The compilation command used was:
gcc-4.0  -c -O3 -DGCC_INLINE -Wall -fno-strict-aliasing -fomit-frame-pointer
-DBOTH_GNUPLOT_AND_X11 -I. -I../src/headers  -o alglin1.o alglin1.i

using gcc-4.0 -O2 or gcc-3.4 -O3 generates correct code.

The problem can be reproduces running the gp interpreter:

1) download the tarball mentionned in the bug report and untar it
2) do 
CC=gcc-4.0 ./Configure
3) do 
make bench

One test-case fails (alglin).
Alternatively, you can do
make gp
./gp
matker([1,2;3,4])
  *** matker: bug in GP (Segmentation Fault), please report

More information about compiler options that fix this problem:
<http://pari.math.u-bordeaux.fr/archives/pari-dev-0505/msg00007.html>

> Can you make a stand-alone testcase?

Not at that time, unfortunately. The bug only occurs inside deeply inlined
code.

-- 
           Summary: [4.0 4.1 regression] miscompilation of PARI/GP on x86
           Product: gcc
           Version: 4.0.2
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: debian-gcc at lists dot debian dot org
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: i486-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23453

[Bug target/23453] [4.0/4.1 regression] miscompilation of PARI/GP on x86

[debian-gcc at lists dot debian dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
      Known to fail|                            |4.0.2 4.1.0
      Known to work|                            |3.4.4
            Summary|[4.0 4.1 regression]        |[4.0/4.1 regression]
                   |miscompilation of PARI/GP on|miscompilation of PARI/GP on
                   |x86                         |x86


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23453

[Bug target/23453] [4.0/4.1 regression] miscompilation of PARI/GP on x86

[debian-gcc at lists dot debian dot org]

------- Additional Comments From debian-gcc at lists dot debian dot org  2005-08-18 07:36 -------
Created an attachment (id=9526)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=9526&action=view)
preprocessed source


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23453

[Bug target/23453] [4.0/4.1 regression] miscompilation of PARI/GP on x86

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-08-18 12:05 -------
We need at least a testcase which links.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Target Milestone|---                         |4.0.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23453

[Bug target/23453] [4.0/4.1 regression] miscompilation of PARI/GP on x86

[debian-gcc at lists dot debian dot org]

------- Additional Comments From debian-gcc at lists dot debian dot org  2005-08-18 13:15 -------
testcase at http://people.debian.org/~doko/tmp/tst.tar.bz2


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23453

[Bug rtl-optimization/23453] [4.0/4.1 regression] miscompilation of PARI/GP on x86

[belyshev at depni dot sinp dot msu dot ru]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
          Component|target                      |rtl-optimization
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-08-18 21:15:51
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23453

[Bug rtl-optimization/23453] [4.0/4.1 regression] miscompilation of PARI/GP on x86 with gcse after reload

[belyshev at depni dot sinp dot msu dot ru]

------- Additional Comments From belyshev at depni dot sinp dot msu dot ru  2005-08-19 01:03 -------
Single-file testcase, compile with "-march=i486 -O2 -fomit-frame-pointer
-fno-strict-aliasing -fgcse-after-reload":

bar ()
{
  exit (0);
}

baz (x)
{
  return x;
}

foo ()
{
  abort ();
}

ker0 (int *x0, int a) 
{
  int *x, *c, *d, p, av, i, j, k, r, t, n, m, *dd;
  n = x0;
  m = x0 [0];
  x = baz (x0);
  if (a) 
    {
      if (m)
	foo ();
      for (k = 1; k <= n; k ++)
	((int **) x) [k] = foo (x [k]);
    }
  for (k = 1; k < m; k ++) 
    c [k] = 0;
  av = k;
  for (k = 0;; k ++) 
    {
      j = bar (x [k], 0, 0, 0);
      if (j > m) 
	{
	  r ++;
	  for (j = 1; j < k; j ++)
	    if (d [j])
	      ((int **) x) [k] [d [j]] = 0;
	}
      else
	{
	  foo (0, x [j]);
	  for (i = k + 1; i; i ++)
	    ((int *) x) [j] = 0;
	  for (t = 1; m; )
	    if (j) 
	      {
		p = x [t];
		for (i = k + 1; i; i ++)
		  x [t] = foo (x [i], foo (p, x [j]));
		if (av)
		  foo (k);
	      }
	}
    }
  *dd = r;
}

int main (void)
{
  int x = 0;
  ker0 (&x, 0);
  abort ();
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23453

[Bug rtl-optimization/23453] [4.0/4.1 regression] miscompilation of PARI/GP on x86 with gcse after reload

[belyshev at depni dot sinp dot msu dot ru]

------- Additional Comments From belyshev at depni dot sinp dot msu dot ru  2005-08-19 19:51 -------
gcse after reload may move loads from stack around stack pointer changes. here
is simple workaround, it is supposed to prevent gcse after reload from touching
expressions containing stack pointer at all.

Index: cse.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cse.c,v
retrieving revision 1.359
diff -u -r1.359 cse.c
--- cse.c	29 Jul 2005 05:57:37 -0000	1.359
+++ cse.c	19 Aug 2005 19:33:49 -0000
@@ -2221,6 +2221,14 @@
 		return 0;
 	      }
 	  }
+	else
+	  {
+	    if (x == stack_pointer_rtx)
+	      {
+		*do_not_record_p = 1;
+		return 0;
+	      }
+	  }
 
 	hash += ((unsigned int) REG << 7);
         hash += (have_reg_qty ? (unsigned) REG_QTY (regno) : regno);


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23453

[Bug rtl-optimization/23453] [4.0/4.1 regression] miscompilation of PARI/GP on x86 with gcse after reload

[mmitchel at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.0.2                       |4.0.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23453

[Bug rtl-optimization/23453] [4.0/4.1 regression] miscompilation of PARI/GP on x86 with gcse after reload

[steven at gcc dot gnu dot org]

------- Comment #10 from steven at gcc dot gnu dot org  2005-11-05 10:48 -------
This doesn't fail for me with the test case from comment #6...  :-(


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23453

[Bug rtl-optimization/23453] [4.0/4.1 regression] miscompilation of PARI/GP on x86 with gcse after reload

[mmitchel at gcc dot gnu dot org]

------- Comment #9 from mmitchel at gcc dot gnu dot org  2005-10-31 05:09 -------
Leaving as P2.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23453

[Bug rtl-optimization/23453] [4.0/4.1 regression] miscompilation of PARI/GP on x86 with gcse after reload

[bonzini at gcc dot gnu dot org]

------- Comment #8 from bonzini at gcc dot gnu dot org  2005-10-14 11:38 -------
> gcse after reload may move loads from stack around stack pointer changes. here
> is simple workaround, it is supposed to prevent gcse after reload from touching
> expressions containing stack pointer at all.

Off the top of my head, if GCSE-after-reload is designed to remove redundant
spills, will it do *anything* with your patch?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23453