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From: "krebbel at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/60181] New: constant folding of complex number incorrect
Date: Thu, 13 Feb 2014 16:19:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60181

            Bug ID: 60181
           Summary: constant folding of complex number incorrect
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: krebbel at gcc dot gnu.org

The following testcase fails on s390x and Power.  Constant folding and runtime
execution of a division of complex numbers produce different results.

The testcase works fine on x86 so it looks like S/390 and Power do something
different here.

It looks somewhat like:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30789

#include <complex.h>
#include <stdio.h>
#include <stdlib.h>

_Complex float __attribute__ ((noinline))
calc (_Complex float a, _Complex float b)
{
  return a / b;
}

int
main (int argc, char **argv)
{
  _Complex float a = calc (10 + 6 * I, 5 + 12 * I);
  _Complex float b = (10 + 6 * I) / (5 + 12 * I);

  printf ("%ap + %ap * i\n", creal (a), cimag (a));
  printf ("%ap + %ap * i\n", creal (b), cimag (b));

  if (a != b)
    abort ();

  return 0;
}

gcc -O0 t.c -o f

./f
0x1.719c08p-1p + -0x1.10a9a8p-1p * i
0x1.719c06p-1p + -0x1.10a9a8p-1p * i
Aborted