Bug 163058

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Description of problem:
The output from the compiler is broken with '-O2' optimisation turned on. After two levels of function calls, the arguments to the final function are the same when they should be different.

Here is a simple program that reproduces the problem:

struct number {
        int value;
        int only_here_to_cause_a_bug_1;
        int only_here_to_cause_a_bug_2;
};

int different(struct number a, struct number b);
int still_different(struct number a, struct number b);

int main(int argc, char **argv)
{
        struct number three, seven;

        three.value = 3;
        seven.value = 7;

        return ! different(three, seven);
}

int different(struct number a, struct number b)
{
        return still_different(b, a);
}

int still_different(struct number a, struct number b) {
        return (a.value != b.value);
}

Version-Release number of selected component (if applicable):
gcc-4.0.0-8

How reproducible:
Always

Steps to Reproduce:
1.Save the above program in a file try.c
2.Run '/usr/bin/gcc -O2 try.c'
3.Run './a.out'
  

Actual Results:  The program exits with an error status

Expected Results:  It should exit without an error status.

Additional info:

Removing the unused fields from the structure removes the problem.

Reducing the optimisation removes the problem.

Reversing the order of the arguments in the call to the function "still_different"   
 removes the problem.