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Date: Wed, 09 Apr 2008 10:33:00 -0000
Subject: [Bug c/35885]  New: unsinged long long and while loop evaluation regression?
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From: "wilbert at jdg dot info" <gcc-bugzilla@gcc.gnu.org>
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The following program:
#include <stdio.h>

int main(int argc, char **argv) {
        unsigned int    testu32a = 0x506f85f;
        unsigned long long      testu64a = 0x9afa246709018f48ULL;

        printf("before: testu64a = %08x%08x, testu32a = %08x\n", (unsigned
int)( testu64a >> 32 ), (unsigned int)( testu64a & 0xffffffff ), testu32a );

        while ((unsigned long long)testu32a * (unsigned long long)0xffffffff <
testu64a)
                testu64a /= 2;

        printf("after: testu64a = %08x%08x, testu32a = %08x\n", (unsigned int)(
testu64a >> 32 ), (unsigned int)( testu64a & 0xffffffff ), testu32a );

        return 0;
}


When compiled under freebsd 6 using "gcc -o test test.c" gives different
results when using gcc 3.4.4 or gcc 4.2.4:

Using 3.4.4:
before: testu64a = 9afa246709018f48, testu32a = 0506f85f
after: testu64a = 04d7d12338480c7a, testu32a = 0506f85f

Using 4.2.4:
before: testu64a = 9afa246709018f48, testu32a = 0506f85f
after: testu64a = 9afa246709018f48, testu32a = 0506f85f


The behavior of 4.2.4 has also been seen on a linux gentoo machine running gcc
4.1.2, a 64bit xp machine running gcc 4.2.1, and a regular xp machine running
gcc 4.2.1.


-- 
           Summary: unsinged long long and while loop evaluation regression?
           Product: gcc
           Version: 4.2.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: wilbert at jdg dot info
 GCC build triplet: several
  GCC host triplet: several
GCC target triplet: several


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35885