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User-Agent: Mozilla/4.76 [en] (X11; U; Linux 2.4.0-4GB i686)

Description of problem:
gcc 2.96-85 produces incorrect code for the function extract in the
example C code.
Rather than accessing the data from the value passed in, the code
takes it from uninitialised data on the stack. So the function
could return any value - usually one unrelated to the value passd
into the function.

Test program:
#include <stdio.h>
struct ieee {
        unsigned int m2:32;
        unsigned int m1:20;
        unsigned int e:11;
        unsigned int s:1;
};

unsigned int extract(double x)
{
        struct ieee *x_as_struct = (struct ieee *) &x;
        return x_as_struct->e;
}

int main(int argc, char **argv[])
{
        printf("Exponent = %u\n",extract(540881114.0));
        return 0;
}

The code generated by gcc for the extrcat function:
.globl extract
        .type    extract,@function
extract:
        pushl   %ebp
        movl    %esp, %ebp
        subl    $8, %esp
        movw    -2(%ebp), %ax
        shrw    $4, %ax
        andl    $2047, %eax
        leave
        ret



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


How reproducible:
Always

Steps to Reproduce:
1. Compile using gcc 2.96-85 using -O2 
2. Run the resulting executable.
3.
	

Actual Results:  Exponent = 1024


Expected Results:  Exponent = 1052


Additional info:

I have checked against GCC 2.95-2, egcs 2.91.66. These produce
the correct result. The option -fno-strict-aliasing will 
make the compiler produce the correct code.