Быстрые мат. функции на си (нашел где-то)

fast_x86_math_func.c

int floor(float a)
{
    int b = (int)a;
    if (a >= 0 || (a - b) == 0)
        return b;
    else
        return b - 1;
}

int trunc(float r)
{
    __asm {
        FLD DWORD [ESP]   ; Load r into ST(0)
        SUB ESP, 0CH
        FSTCW [ESP]
        FSTCW [ESP+2]
        OR WORD[ESP+2], 0F00H
        FLDCW [ESP+2]
        FISTP QWORD[ESP+4]
        FLDCW [ESP]
        POP ECX
        POP EAX
        POP EDX
    }
}

int round(float r)
{
    __asm {
        FLD DWORD [ESP]   ; Load r into ST(0)
        FISTP DWORD [ESP] ; Store ST(0) in [ESP] and pop ST(0)
        POP EAX           ; EAX = [ESP]
    }
}

int truncate_int(double x)
{
    assert(x > static_cast(INT_MIN / 2) – 1.0);
    assert(x < static_cast(INT_MAX / 2) + 1.0);
    const float round_towards_m_i = -0.5f;
    int i;
    __asm {
        fld x
        fadd st, st(0)
        fabs
        fadd round_towards_m_i
        fistp i
        sar i, 1
    }
    if (x < 0)
        i = -i;
    return i;
}