c/1910: incorrect long long return value with -O2 optimization

[djk at super dot org]

>Number:         1910
>Category:       c
>Synopsis:       incorrect long long return value with -O2 optimization
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Thu Feb 08 05:16:02 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     daniel kopetzky
>Release:        GCC: (GNU) 2.97 20010207 (experimental)
>Organization:
>Environment:
intel
>Description:
-O2 generates incorrect code and causes the following
example routine to return a long long value from an
uninitialized stack location.

struct cl {
        int one, two;
};
const char *error = "edx should get 0, eax should get ebp[4]";
long long broken (int a){
        struct cl val;
        val.one = a;
        val.two = 0;

        return *(long long *)&val;
}

--------------
the codesourcery compile server gave this answer today:
        .file   "@5412.7.c"
        .version        "01.01"
gcc2_compiled.:
.globl error
        .section        .rodata
        .align 32
.LC0:
        .string "edx should get 0, eax should get ebp[4]"
        .data
        .align 4
        .type   error,@object
        .size   error,4
error:
        .long   .LC0
        .text
        .align 4
.globl broken
        .type   broken,@function
broken:
        pushl   %ebp
        movl    %esp, %ebp
        subl    $8, %esp
        movl    -8(%ebp), %eax
        movl    -4(%ebp), %edx
        leave
        ret
.Lfe1:
        .size   broken,.Lfe1-broken
        .ident  "GCC: (GNU) 2.97 20010207 (experimental)"

------------------------

Looks like the optimizer removed the two assignments to
the structure (one is a parameter, the other is a zero).
>How-To-Repeat:
gcc -O2 -S bug.c
inspect eax & edx values returned from function. 
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: