Missing if optimization

[Uros Bizjak]

Hello!

The if optimization, which produces quite optimized code for integer 
case is missing for floatin-point compares.

This code:

int test(int a) {
        return a == 0 ? 0 : (a > 0 ? 1 : -1);
}

produces (with -O2  -fomit-frame-pointer):

test:
        xorl    %eax, %eax
        cmpl    $0, 4(%esp)
        je      .L4
        setg    %al
        movzbl  %al, %eax
        leal    -1(%eax,%eax), %eax
.L4:
        ret

However, fp compares:

double testf(double a) {
        return a == 0.0 ? 0.0 : (a > 0.0 ? 1.0 : -1.0);
}

Produce somehow unoptimized code (-O2 -ffast-math -fomit-frame-pointer):

testf:
        fldl    4(%esp)
        ftst
        fnstsw  %ax
        sahf
        jne     .L9
        fstp    %st(0)
        fldz
        ret
        .p2align 4,,7
.L9:
        ftst
        fnstsw  %ax
        fstp    %st(0)
        sahf
        ja      .L12
        flds    .LC1
        ret
        .p2align 4,,7
.L12:
        fld1
        .p2align 4,,2
        ret

There is no need for second fp compare, two conditional jumps after 
first fp compare would be enough.

Uros.