direct floating point equal comparison fails on 32-bit emulation

[dlangBugzillaToGithub]

Seb reported this on 2016-07-27T17:05:54Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=16327

Description

--------
S fun(S)(in S x)
{
    return -1 / x;
}

unittest
{
    import std.meta : AliasSeq;
    foreach (S; AliasSeq!(float, double, real))
    {
        import std.stdio;
        S i = fun!S(3);
        assert(i == S(-1) / 3); // this lines passes
        assert(fun!S(3) == S(-1) / 3); // error
    }
}
--------

I tested 32-bit with this command on a x86_64 platform.

rdmd -main -unittest -m32

Assembler:
----------

.text._D3foo14__unittestL6_1FZv segment
        assume  CS:.text._D3foo14__unittestL6_1FZv
_D3foo14__unittestL6_1FZv:
                push    EBP
                mov     EBP,ESP
                sub     ESP,4
                push    dword ptr FLAT:.rodata[08h]
                call      _D3foo15__T8crazyfunTfZ8crazyfunFNaNbNiNfxfZf@PC32
                fstp    float ptr -4[EBP]
                fld     float ptr -4[EBP]
                fld     float ptr _D3foo12__ModuleInfoZ@SYM32[0Dh]
                fucompp ST(1),ST
                fstsw   AX
                sahf
                jp      L26
                je      L30
L26:            mov     EAX,0Eh
                call      _D3foo15__unittest_failFiZv@PC32
L30:            push    dword ptr _TMP3@SYM32[0Ah]
                call      _D3foo15__T8crazyfunTfZ8crazyfunFNaNbNiNfxfZf@PC32
                fld     float ptr _TMP3@SYM32[019h]
                fucompp ST(1),ST
                fstsw   AX
                sahf
                jp      L4A
                je      L54
L4A:            mov     EAX,0Fh
                call      _D3foo15__unittest_failFiZv@PC32
L54:            leave
                ret
                nop
                nop
.text._D3foo14__unittestL6_1FZv ends
.text._D3foo15__T8crazyfunTfZ8crazyfunFNaNbNiNfxfZf     segment
        assume  CS:.text._D3foo15__T8crazyfunTfZ8crazyfunFNaNbNiNfxfZf
_D3foo15__T8crazyfunTfZ8crazyfunFNaNbNiNfxfZf:
                fld     float ptr FLAT:.rodata[0Ah]
                fdiv    float ptr 4[ESP]
                ret     4
                nop
                nop
                nop
.text._D3foo15__T8crazyfunTfZ8crazyfunFNaNbNiNfxfZf     ends