A question about redudant load elimination

["Jiangning Liu" <jiangning dot liu at arm dot com>]

Hi,

For this test case,

int x;
extern void f(void);

void g(int *a)
{
        a[x] = 1;
        if (x == 100)
                f();
        a[x] = 2;
}

For trunk, the x86 assembly code is like below,

        movl    x, %eax
        movl    16(%esp), %ebx
        movl    $1, (%ebx,%eax,4)
        movl    x, %eax   // Is this a redundant one?
        cmpl    $100, %eax
        je      .L4
        movl    $2, (%ebx,%eax,4)
        addl    $8, %esp
        .cfi_remember_state
        .cfi_def_cfa_offset 8
        popl    %ebx
        .cfi_restore 3
        .cfi_def_cfa_offset 4
        ret
        .p2align 4,,7
        .p2align 3
.L4:
        .cfi_restore_state
        call    f
        movl    x, %eax
        movl    $2, (%ebx,%eax,4)
        addl    $8, %esp
        .cfi_def_cfa_offset 8
        popl    %ebx
        .cfi_restore 3
        .cfi_def_cfa_offset 4
        Ret

Is the 2nd "movl x, %eax" is a redundant one for single thread programming
model? If yes, can this be optimized away?

Thanks,
-Jiangning