gcc produces incorrect minimization code

[Matthias Klose <doko@klose.in-berlin.de>]

>Submitter-Id:	net
>Originator:	camm@enhanced.com
>Organization:	The Debian Project
>Confidential:	no
>Synopsis:	
>Severity:	non-critical
>Priority:	low
>Category:	c
>Class:		wrong-code
>Release:	3.1 (Debian) (Debian unstable)
>Environment:
System: Debian GNU/Linux (unstable)
Architecture: i686
	
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Installed/Config-files/Unpacked/Failed-config/Half-installed
|/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err: uppercase=bad)
||/ Name           Version        Description
+++-==============-==============-============================================
ii  gcc-3.1        3.1-2          The GNU C compiler.
ii  binutils       2.12.90.0.7-1  The GNU assembler, linker and binary utiliti
ii  libc6          2.2.5-6        GNU C Library: Shared libraries and Timezone
host: i386-linux
configured with: /mnt/data/gcc-3.1/gcc-3.1-3.1ds2/src/configure -v --enable-languages=c,c++,java,f77,proto,objc,ada --prefix=/usr --mandir=$\(prefix\)/share/man --infodir=$\(prefix\)/share/info --with-gxx-include-dir=$\(prefix\)/include/g++-v3-3.1 --enable-shared --with-system-zlib --enable-long-long --enable-nls --without-included-gettext --enable-clocale=gnu --enable-threads=posix --enable-java-gc=boehm --enable-objc-gc i386-linux
>Description:
[ Reported to the Debian BTS as report #40189.
  Please CC 40189@bugs.debian.org on replies.
  Log of report can be found at http://bugs.debian.org/40189 ]

The following program inconsistently chooses minimal
array elements in case of equal elements being present.

intech19:~$ gcc -g ttr.c -o ttr
intech19:~$ ./ttr
ir=0
ir=3

On all other optimization levels (-Os, -O1 and up) the "expected"
output is:

intech19:~$ ./ttr
ir=0
ir=0

Here is the code (ttr.c):
------------------------
#include <stdio.h>
#include <float.h>
#include <math.h>


int
main() {

  double a[4]={0.006776,2.5,3.0,0.006776},
         w[4]={0.000030,3.7,3.0,0.000030},
         t,
         amin;
  int ir, i, nr = 4;
  double tol = 9.31322574615479e-10 * 3.0;

  for (i=0, ir=-1, amin = DBL_MAX; i < nr; i++) 
    if (a[i] > tol) {
      t = w[i] / a[i];
      if (t < amin || ir == -1) {
	amin = t;
	ir = i;
      }
    }
  
  printf("ir=%d\n", ir);

  for (i = 0, ir = -1, amin = DBL_MAX; i < nr; i++) 
    if (a[i] > tol && ((t = w[i] / a[i]) < amin || ir == -1)) {
	amin = t;
	ir = i;
      }
  
  printf("ir=%d\n", ir);

  return 0;
}
	
>How-To-Repeat:
	
>Fix:
	


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