Again -march=i686 -O bug

[Gerhard Heinzel]

Sorry to repeat this, but the bug is STILL present in the just announced 
19981130 snapshot.

The program below is miscompiled and prints "NaN" instead of "0", when
compiled with -march=i686 -O.


--------------- Compiler specs -----------------------

Reading specs from
/usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.92.25/specs
gcc version egcs-2.92.25 19981130 (gcc2 ss-980609 experimental)
 /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.92.25/cpp -lang-c -v
-undef -D__GNUC__=2 -D__GNUC_MINOR__=92 -D__ELF__ -Dunix -D__i386__ -Dlinux
-D__ELF__ -D__unix__ -D__i386__ -D__linux__ -D__unix -D__linux
-Asystem(posix) -D__OPTIMIZE__ -Acpu(i386) -Amachine(i386) -Di386 -D__i386
-D__i386__ -Di686 -Dpentiumpro -D__i686 -D__i686__ -D__pentiumpro
-D__pentiumpro__ err.c /tmp/ccZssesp.i
GNU CPP version egcs-2.92.25 19981130 (gcc2 ss-980609 experimental) (i386
Linux/ELF)
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.92.25/../../../../i686-pc-linux-gnulibc1/include
 /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.92.25/include
 /usr/include
End of search list.
 /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.92.25/cc1
/tmp/ccZssesp.i -quiet -dumpbase err.c -march=i686 -O -version -o
/tmp/ccIQYx5O.s
GNU C version egcs-2.92.25 19981130 (gcc2 ss-980609 experimental)
(i686-pc-linux-gnulibc1) compiled by GNU C version egcs-2.92.25 19981130
(gcc2 ss-980609 experimental).
 as -V -Qy -o /tmp/ccp1KMqn.o /tmp/ccIQYx5O.s
GNU assembler version 2.8.1 (i486-linux), using BFD version 2.8.1
 /usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.92.25/collect2 -m
elf_i386 -dynamic-linker /lib/ld-linux.so.1 -o err /usr/lib/crt1.o
/usr/lib/crti.o
/usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.92.25/crtbegin.o
-L/usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.92.25
-L/usr/local/i686-pc-linux-gnulibc1/lib -L/usr/local/lib /tmp/ccp1KMqn.o
-lgcc -lc -lgcc
/usr/local/lib/gcc-lib/i686-pc-linux-gnulibc1/egcs-2.92.25/crtend.o
/usr/lib/crtn.o
 

-------------------- Test program -------------------------------

#include <stdio.h>
#include <math.h>
#define SIZE 10

int
main (void)
{
  int i, j, k;
  double a[SIZE * SIZE], ainv[SIZE * SIZE];
  double diff, sum, soll, maxd;

  /* matrix addressing : a(i,j) = a[n*i+j] */

  /* Normally here 'a' is a double matrix and 'ainv' its inverse */
  /* For testing, set 'a' and 'ainv' as unity matrices */
  for (i = 0; i < SIZE; i++)
    for (j = 0; j < SIZE; j++)
      a[i * SIZE + j] = ainv[i * SIZE + j] = ((i == j) ? 1 : 0);

  /* compute the product a*ainv element by element and compare to
     unity matrix */

  maxd = 0;			/* maximum of difference */
  for (i = 0; i < SIZE; i++)
    for (j = 0; j < SIZE; j++)
      /* compute element (i,j) of product */
      {
/*1*/	sum = 0;
/*2*/	soll = ((i == j) ? 1 : 0);	/* this should be the result */
	for (k = 0; k < SIZE; k++)
	  sum += a[i * SIZE + k] * ainv[k * SIZE + j];
	diff = fabs (sum - soll);	/* measure difference */
	if (diff > maxd)	/* record maximum difference */
	  maxd = diff;
      }
  printf ("maxd=%g \n", maxd);
  return 0;
}


Cheers

Gerhard

=====================================================================
 Gerhard Heinzel                            E-mail:   ghh@mpq.mpg.de
 Max-Planck-Institut fuer Quantenoptik   Phone: +49(89)32905-268/252
 Hans-Kopfermann-Str. 1            Phone (30m Lab): +49(89)3299-3282
 D-85748 Garching                              Fax: +49(89)32905-200  
 Germany                                        http://130.183.90.63
=====================================================================