This is the most recent I have. I haven't used it on the GP2X yet, but the ARM ASM parts should work anyway. If yo know how to use functions this is pretty easy to use...
CODE
 
/*
 * $Id: math-sll.c,v 1.15 2002/08/20 18:01:54 andrewm Exp $
 *
 * Changed by CHUI
 *
 * Purpose
 *    A fixed point (31.32 bit) math library.
 *
 * Description
 *    Floating point packs the most accuracy in the available bits, but it
 *    often provides more accuracy than is required.  It is time consuming to
 *    carry the extra precision around, particularly on platforms that don't
 *    have a dedicated floating point processor.
 *
 *    This library is a compromise.  All math is done using the 64 bit signed
 *    "long long" format (sll), and is not intended to be portable, just as
 *    fast as possible.  Since "long long" is a elementary type, it can be
 *    passed around without resorting to the use of pointers.  Since the
 *    format used is fixed point, there is never a need to do time consuming
 *    checks and adjustments to maintain normalized numbers, as is the case
 *    in floating point.
 *
 *    Simply put, this library is limited to handling numbers with a whole
 *    part of up to 2^31 - 1 = 2.147483647e9 in magnitude, and fractional
 *    parts down to 2^-32 = 2.3283064365e-10 in magnitude.  This yields a
 *    decent range and accuracy for many applications.
 *
 * IMPORTANT
 *    No checking for arguments out of range (error).
 *    No checking for divide by zero (error).
 *    No checking for overflow (error).
 *    No checking for underflow (warning).
 *    Chops, doesn't round.
 *
 * Functions
 *    sll dbl2sll(double x)            double -> sll
 *    double slldbl(sll x)            sll -> double
 *
 *    sll slladd(sll x, sll y)        x + y
 *    sll sllsub(sll x, sll y)        x - y
 *    sll sllmul(sll x, sll y)        x * y
 *    sll slldiv(sll x, sll y)        x / y
 *
 *    sll sllinv(sll v)            1 / x
 *    sll sllmul2(sll x)            x * 2
 *    sll sllmul4(sll x)            x * 4
 *    sll sllmul2n(sll x, int n)        x * 2^n, 0 <= n <= 31
 *    sll slldiv2(sll x)            x / 2
 *    sll slldiv4(sll x)            x / 4
 *    sll slldiv2n(sll x, int n)        x / 2^n, 0 <= n <= 31
 *
 *    sll sllcos(sll x)            cos x
 *    sll sllsin(sll x)            sin x
 *    sll slltan(sll x)            tan x
 *    sll sllatan(sll x)            atan x
 *
 *    sll sllexp(sll x)            e^x
 *    sll slllog(sll x)            ln x
 *
 *    sll sllpow(sll x, sll y)        x^y
 *    sll sllsqrt(sll x)            x^(1 / 2)
 *
 */
#ifndef MATHSLL_H
#define MATHSLL_H
#ifdef __cplusplus
extern "C" {
#endif
#ifndef USE_FIXED_POINT
#include <math.h>
/*
typedef float sll;
typedef float ull;
*/
typedef double sll;
typedef double ull;
#define int2sll(X)    ((sll) (X))
#define sllvalue(X)    (X)
#define sll2int(X)    ((int) (X))
#define sll_abs(X)    ((sll)fabs((double)X))
#define sllabs(X)    ((sll)fabs((double)X))
#define sllint(X)    ((sll)floor((double)X))
#define sllfrac(X)    ((X) - ((sll)sll2int(X)))
#define sllneg(X)    (-(X))
#define slladd(X,Y)    ((X) + (Y))
#define sllsub(X,Y)    ((X) - (Y))
#define sllmul(X,Y)    ((X) * (Y))
#define slldiv(X,Y)    ((X) / (Y))
#define sll2dbl(X)    ((double)(X))
#define dbl2sll(X)    ((sll)(X))
#define sllinv(X)    (((sll)1.0) / (X))
#define sllmul2(X)    (((sll)2.0) * (X))
#define sllmul4(X)    (((sll)4.0) * (X))
#define sllmul2n(X,N)    (((sll)(1<<N)) * (X))
#define slldiv2(X)    ((X) / ((sll)2.0))
#define slldiv4(X)    ((X) / ((sll)4.0))
#define slldiv2n(X,N)    ((X) / ((sll)(1<<N)))
#define sllcos(X)    ((sll)cos((double)(X)))
#define sllsin(X)    ((sll)sin((double)(X)))
#define slltan(X)    ((sll)tan((double)(X)))
#define sllatan(X)    ((sll)atan((double)(X)))
#define sllexp(X)    ((sll)exp((double)(X)))
#define slllog(X)    ((sll)log((double)(X)))
#define sllpow(X)    ((sll)pow((double)(X)))
#define sllsqrt(X)    ((sll)sqrt((double)(X)))
#define sllrotr(X,N)    ((X) / ((sll)(1<<N)))
#define sllrotl(X,N)    ((X) * ((sll)(1<<N)))
#define SLL_CONST_0        ((sll)0.0)
#define SLL_CONST_1        ((sll)1.0)
#define SLL_CONST_2        ((sll)2.0)
#define SLL_CONST_3        ((sll)3.0)
#define SLL_CONST_4        ((sll)4.0)
#define SLL_CONST_10        ((sll)10.0)
#define SLL_CONST_15        ((sll)15.0)
#define SLL_CONST_1_2        ((sll)0.5)
#define SLL_CONST_1_3        ((sll)0.33333333333333333333333333333333)
#define SLL_CONST_1_4        ((sll)0.25)
#define SLL_CONST_1_5        ((sll)0.2)
#define SLL_CONST_1_6        ((sll)0.16666666666666666666666666666667)
#define SLL_CONST_1_7        ((sll)0.14285714285714285714285714285714)
#define SLL_CONST_1_8        ((sll)0.125)
#define SLL_CONST_1_9        ((sll)0.11111111111111111111111111111111)
#define SLL_CONST_1_10        ((sll)0.10)
#define SLL_CONST_1_11        ((sll)0.090909090909090909090909090909091)
#define SLL_CONST_1_12        ((sll)0.083333333333333333333333333333333)
#define SLL_CONST_1_20        ((sll)0.05)
#define SLL_CONST_1_30        ((sll)0.033333333333333333333333333333333)
#define SLL_CONST_1_42        ((sll)0.023809523809523809523809523809524)
#define SLL_CONST_1_56        ((sll)0.017857142857142857142857142857143)
#define SLL_CONST_1_72        ((sll)0.013888888888888888888888888888889)
#define SLL_CONST_1_90        ((sll)0.011111111111111111111111111111111)
#define SLL_CONST_1_110        ((sll)0.0090909090909090909090909090909091)
#define SLL_CONST_1_132        ((sll)0.0075757575757575757575757575757576)
#define SLL_CONST_1_156        ((sll)0.0064102564102564102564102564102564)
#define SLL_CONST_E        ((sll)2.7182818284590452354)
#define SLL_CONST_1_E        ((sll)0.36787944117144232159014926384893)
#define SLL_CONST_1_SQRTE    ((sll)0.13533528323661269189004515421424)
#define SLL_CONST_LOG10_E    ((sll)0.43429448190325182765747371064254)
#define SLL_CONST_PI        ((sll)3.1415926535897932384626433832795)
#define SLL_CONST_2PI        ((sll)6.283185307179586476925286766559)
#define SLL_CONST_4PI        ((sll)12.566370614359172953850573533118)
#define SLL_CONST_PI_2        ((sll)1.5707963267948966192313216916398)
#define SLL_CONST_PI_4        ((sll)0.78539816339744830961566084581988)
#define SLL_CONST_PI_8        ((sll)0.3926990816987242)
#define SLL_CONST_PI_12         ((sll)0.26179938779914943653855361527329)
#define SLL_CONST_1_PI        ((sll)0.31830988618379067153776752674503)
#define SLL_CONST_2_PI        ((sll)3.1415926535897932384626433832795)
#define SLL_CONST_ATAN_1    ((sll)0.785398)
#else
/* Data types */
typedef signed long long sll;
typedef unsigned long long ull;
/* Macros */
#define int2sll(X)    (((sll) (X)) << 32)
// #define sllvalue(X)    (sll2dbl(X))
#define sllvalue(X)    (X)
#define sll2int(X)    ((int) ((X) >> 32))
#define sll_abs(X)    ((X) & 0xefffffffffffffffLL)
#define sllabs(A)    (((A)<SLL_CONST_0)? -(A)

A))
#define sllint(X)    ((X) & 0xffffffff00000000LL)
#define sllfrac(X)    ((X) & 0x00000000ffffffffLL)
#define sllneg(X)    (-(X))
#define _slladd(X,Y)    ((X) + (Y))
#define _sllsub(X,Y)    ((X) - (Y))
#define sllrotl(X,N)    ((X)<<N)
#define sllrotr(X,N)    ((X)>>N)
/* Constants (converted from double) */
#define SLL_CONST_0        0x0000000000000000LL
#define SLL_CONST_1        0x0000000100000000LL
#define SLL_CONST_2        0x0000000200000000LL
#define SLL_CONST_3        0x0000000300000000LL
#define SLL_CONST_4        0x0000000400000000LL
#define SLL_CONST_10    0x0000000a00000000LL
#define SLL_CONST_15    0x0000000f00000000LL
#define SLL_CONST_1_2    0x0000000080000000LL
#define SLL_CONST_1_3    0x0000000055555555LL
#define SLL_CONST_1_4    0x0000000040000000LL
#define SLL_CONST_1_5    0x0000000033333333LL
#define SLL_CONST_1_6    0x000000002aaaaaaaLL
#define SLL_CONST_1_7    0x0000000024924924LL
#define SLL_CONST_1_8    0x0000000020000000LL
#define SLL_CONST_1_9    0x000000001c71c71cLL
#define SLL_CONST_1_10    0x0000000019999999LL
#define SLL_CONST_1_11    0x000000001745d174LL
#define SLL_CONST_1_12    0x0000000015555555LL
#define SLL_CONST_1_20    0x000000000cccccccLL
#define SLL_CONST_1_30    0x0000000008888888LL
#define SLL_CONST_1_42    0x0000000006186186LL
#define SLL_CONST_1_56    0x0000000004924924LL
#define SLL_CONST_1_72    0x00000000038e38e3LL
#define SLL_CONST_1_90    0x0000000002d82d82LL
#define SLL_CONST_1_110    0x000000000253c825LL
#define SLL_CONST_1_132    0x0000000001f07c1fLL
#define SLL_CONST_1_156    0x0000000001a41a41LL
#define SLL_CONST_E        0x00000002b7e15162LL
#define SLL_CONST_1_E    0x000000005e2d58d8LL
#define SLL_CONST_SQRTE    0x00000001a61298e1LL
#define SLL_CONST_1_SQRTE    0x000000009b4597e3LL
#define SLL_CONST_LOG2_E    0x0000000171547652LL
#define SLL_CONST_LOG10_E    0x000000006f2dec54LL
#define SLL_CONST_LN2    0x00000000b17217f7LL
#define SLL_CONST_LN10    0x000000024d763776LL
#define SLL_CONST_PI    0x00000003243f6a88LL
#define SLL_CONST_2PI    0x00000006487ED510LL
#define SLL_CONST_4PI    0x0000000C90FDAA22LL
#define SLL_CONST_PI_2    0x00000001921fb544LL
#define SLL_CONST_PI_4    0x00000000c90fdaa2LL
#define SLL_CONST_PI_8  0x000000006487ED51LL
#define SLL_CONST_PI_12 0x00000000430548E0LL
#define SLL_CONST_1_PI    0x00000000517cc1b7LL
#define SLL_CONST_2_PI    0x00000000a2f9836eLL
#define SLL_CONST_2_SQRTPI    0x0000000120dd7504LL
#define SLL_CONST_SQRT2    0x000000016a09e667LL
#define SLL_CONST_1_SQRT2    0x00000000b504f333LL
#define SLL_CONST_ATAN_1    0x00000000C90FD7E4LL
static __inline__ double sll2dbl(sll s)
{
    union {
        double d;
        unsigned u[2];
        ull _ull;
        sll _sll;
    } in, retval;
    register unsigned exp;
    register unsigned flag;
    if (s == 0)
        return 0.0;
    /* Move into memory as args might be passed in regs */
    in._sll = s;
    /* Handle the negative flag */
    if (in._sll < 1) {
        flag = 0x80000000;
        in._ull = sllneg(in._sll);
    } else
        flag = 0x00000000;
    /* Normalize */
    for (exp = 1053; in._ull && (in.u[1] & 0x80000000) == 0; exp--) {
        in._ull <<= 1;
    }
    in._ull <<= 1;
    exp++;
    in._ull >>= 12;
    retval._ull = in._ull;
    retval.u[1] |= flag | (exp << 20);
#if defined(__arm__)
    /* ARM architecture has a big-endian double */
    exp = retval.u[0];
    retval.u[0] = retval.u[1];
    retval.u[1] = exp;
#endif /* defined(__arm__) */
    return retval.d;
}
static __inline__ sll slladd(sll x, sll y)
{
    return (x + y);
}
static __inline__ sll sllsub(sll x, sll y)
{
    return (x - y);
}
/*
 * Let a = A * 2^32 + a_hi * 2^0 + a_lo * 2^(-32)
 * Let b = B * 2^32 + b_hi * 2^0 + b_lo * 2^(-32)
 *
 * Where:
 *   *_hi is the integer part
 *   *_lo the fractional part
 *   A and B are the sign (0 for positive, -1 for negative).
 *
 * a * b = (A * 2^32 + a_hi * 2^0 + a_lo * 2^-32)
 *       * (B * 2^32 + b_hi * 2^0 + b_lo * 2^-32)
 *
 * Expanding the terms, we get:
 *
 *     = A * B * 2^64 + A * b_h * 2^32 + A * b_l * 2^0
 *     + a_h * B * 2^32 + a_h * b_h * 2^0 + a_h * b_l * 2^-32
 *     + a_l * B * 2^0 + a_l * b_h * 2^-32 + a_l * b_l * 2^-64
 *
 * Grouping by powers of 2, we get:
 *
 *     = A * B * 2^64
 *     Meaningless overflow from sign extension - ignore
 *
 *     + (A * b_h + a_h * B) * 2^32
 *     Overflow which we can't handle - ignore
 *
 *     + (A * b_l + a_h * b_h + a_l * B) * 2^0
 *     We only need the low 32 bits of this term, as the rest is overflow
 *
 *     + (a_h * b_l + a_l * b_h) * 2^-32
 *     We need all 64 bits of this term
 *
 *     +  a_l * b_l * 2^-64
 *     We only need the high 32 bits of this term, as the rest is underflow
 *
 * Note that:
 *   a > 0 && b > 0: A =  0, B =  0 and the third term is a_h * b_h
 *   a < 0 && b > 0: A = -1, B =  0 and the third term is a_h * b_h - b_l
 *   a > 0 && b < 0: A =  0, B = -1 and the third term is a_h * b_h - a_l
 *   a < 0 && b < 0: A = -1, B = -1 and the third term is a_h * b_h - a_l - b_l
 */
#if defined(__arm__)
static __inline__ sll sllmul(sll left, sll right)
{
    /*
     * From gcc/config/arm/arm.h:
     *   In a pair of registers containing a DI or DF value the 'Q'
     *   operand returns the register number of the register containing
     *   the least significant part of the value.  The 'R' operand returns
     *   the register number of the register containing the most
     *   significant part of the value.
     */
    sll retval;
    __asm__ (
        "@ sllmul\n\t"
        "umull    %R0, %Q0, %Q1, %Q2\n\t"
        "mul    %R0, %R1, %R2\n\t"
        "umlal    %Q0, %R0, %Q1, %R2\n\t"
        "umlal    %Q0, %R0, %Q2, %R1\n\t"
            "tst    %R1, #0x80000000\n\t"
            "subne    %R0, %R0, %Q2\n\t"
            "tst    %R2, #0x80000000\n\t"
            "subne    %R0, %R0, %Q1\n\t"
        : "=&r" (retval)
        : "%r" (left), "r" (right)
        : "cc"
    );
    return retval;
}
#elif defined(__i386__)
static __inline__ sll sllmul(sll left, sll right)
{
    register sll retval;
    __asm__(
        "# sllmul\n\t"
        "    movl    %1, %%eax\n\t"
        "    mull     %3\n\t"
        "    movl    %%edx, %%ebx\n\t"
        "\n\t"
        "    movl    %2, %%eax\n\t"
        "    mull     %4\n\t"
        "    movl    %%eax, %%ecx\n\t"
        "\n\t"
        "    movl    %1, %%eax\n\t"
        "    mull    %4\n\t"
        "    addl    %%eax, %%ebx\n\t"
        "    adcl    %%edx, %%ecx\n\t"
        "\n\t"
        "    movl    %2, %%eax\n\t"
        "    mull    %3\n\t"
        "    addl    %%ebx, %%eax\n\t"
        "    adcl    %%ecx, %%edx\n\t"
        "\n\t"
        "    btl    $31, %2\n\t"
        "    jnc    1f\n\t"
        "    subl    %3, %%edx\n\t"
        "1:    btl    $31, %4\n\t"
        "    jnc    1f\n\t"
        "    subl    %1, %%edx\n\t"
        "1:\n\t"
        : "=&A" (retval)
        : "m" (left), "m" (((unsigned *) &left)[1]),
          "m" (right), "m" (((unsigned *) &right)[1])
        : "ebx", "ecx", "cc"
    );
    return retval;
}
#else
/* Plain C version: not optimal but portable. */
#warning Fixed Point no optimal
static __inline__ sll sllmul(sll a, sll b)
{
    unsigned int a_lo, b_lo;
    signed int a_hi, b_hi;
    sll x;
    a_lo = a;
    a_hi = (ull) a >> 32;
    b_lo = b;
    b_hi = (ull) b >> 32;
    x = ((ull) (a_hi * b_hi) << 32)
      + (((ull) a_lo * b_lo) >> 32)
      + (sll) a_lo * b_hi
      + (sll) b_lo * a_hi;
    return x;
}
#endif
static __inline__ sll sllinv(sll v)
{
    int sgn = 0;
    sll u;
    ull s = -1; //0xFFFFFFFFFFFFFFFF; //-1;
    /* Use positive numbers, or the approximation won't work */
    if (v < SLL_CONST_0) {
        v = sllneg(v);
        sgn = 1;
    }
    /* An approximation - must be larger than the actual value */
    for (u = v; u; ((ull)u) >>= 1)
        s >>= 1;
    /* Newton's Method */
    u = sllmul(s, _sllsub(SLL_CONST_2, sllmul(v, s)));
    u = sllmul(u, _sllsub(SLL_CONST_2, sllmul(v, u)));
    u = sllmul(u, _sllsub(SLL_CONST_2, sllmul(v, u)));
    u = sllmul(u, _sllsub(SLL_CONST_2, sllmul(v, u)));
    u = sllmul(u, _sllsub(SLL_CONST_2, sllmul(v, u)));
    u = sllmul(u, _sllsub(SLL_CONST_2, sllmul(v, u)));
    return ((sgn) ? sllneg(u): u);
}
static __inline__ sll slldiv(sll left, sll right)
{
    return sllmul(left, sllinv(right));
}
static __inline__ sll sllmul2(sll x)
{
    return x << 1;
}
static __inline__ sll sllmul4(sll x)
{
    return x << 2;
}
static __inline__ sll sllmul2n(sll x, int n)
{
    sll y;
#if defined(__arm__)
    /*
     * On ARM we need to do explicit assembly since the compiler
     * doesn't know the range of n is limited and decides to call
     * a library function instead.
     */
    __asm__ (
        "@ sllmul2n\n\t"
        "mov    %R0, %R1, lsl %2\n\t"
        "orr    %R0, %R0, %Q1, lsr %3\n\t"
        "mov    %Q0, %Q1, lsl %2\n\t"
        : "=r" (y)
        : "r" (x), "rM" (n), "rM" (32 - n)
    );
#else
    y = x << n;
#endif
    return y;
}
static __inline__ sll slldiv2(sll x)
{
    return x >> 1;
}
static __inline__ sll slldiv4(sll x)
{
    return x >> 2;
}
static __inline__ sll slldiv2n(sll x, int n)
{
    sll y;
#if defined(__arm__)
    /*
     * On ARM we need to do explicit assembly since the compiler
     * doesn't know the range of n is limited and decides to call
     * a library function instead.
     */
    __asm__ (
        "@ slldiv2n\n\t"
        "mov    %Q0, %Q1, lsr %2\n\t"
        "orr    %Q0, %Q0, %R1, lsl %3\n\t"
        "mov    %R0, %R1, asr %2\n\t"
        : "=r" (y)
        : "r" (x), "rM" (n), "rM" (32 - n)
    );
#else
    y = x >> n;
#endif
    return y;
}
/*
 * Unpack the IEEE floating point double format and put it in fixed point
 * sll format.
 */
static __inline__ sll dbl2sll(double dbl)
{
    union {
        double d;
        unsigned u[2];
        ull _ull;
        sll _sll;
    } in, retval;
    register unsigned exp;
    /* Move into memory as args might be passed in regs */
    in.d = dbl;
#if defined(__arm__)
    /* ARM architecture has a big-endian double */
    exp = in.u[0];
    in.u[0] = in.u[1];
    in.u[1] = exp;
#endif /* defined(__arm__) */
    /* Leading 1 is assumed by IEEE */
    retval.u[1] = 0x40000000;
    /* Unpack the mantissa into the unsigned long */
    retval.u[1] |= (in.u[1] << 10) & 0x3ffffc00;
    retval.u[1] |= (in.u[0] >> 22) & 0x000003ff;
    retval.u[0] = in.u[0] << 10;
    /* Extract the exponent and align the decimals */
    exp = (in.u[1] >> 20) & 0x7ff;
    if (exp)
        retval._ull >>= 1053 - exp;
    else
        return 0L;
    /* Negate if negative flag set */
    if (in.u[1] & 0x80000000)
        retval._sll = -retval._sll;
    return retval._sll;
}
static __inline__ sll float2sll(float f)
{
    return dbl2sll((double)f);
}
static __inline__ float sll2float(sll s)
{
    return ((float)sll2dbl(s));
}
/*
 * Calculate cos x where -pi/4 <= x <= pi/4
 *
 * Description:
 *    cos x = 1 - x^2 / 2! + x^4 / 4! - ... + x^(2N) / (2N)!
 *    Note that (pi/4)^12 / 12! < 2^-32 which is the smallest possible number.
 */
static __inline__ sll _sllcos(sll x)
{
    sll retval, x2;
    x2 = sllmul(x, x);
    /*
     * cos x = t0 + t1 + t2 + t3 + t4 + t5 + t6
     *
     * f0 =  0! =  1
     * f1 =  2! =  2 *  1 * f0 =   2 * f0
     * f2 =  4! =  4 *  3 * f1 =  12 x f1
     * f3 =  6! =  6 *  5 * f2 =  30 * f2
     * f4 =  8! =  8 *  7 * f3 =  56 * f3
     * f5 = 10! = 10 *  9 * f4 =  90 * f4
     * f6 = 12! = 12 * 11 * f5 = 132 * f5
     *
     * t0 = 1
     * t1 = -t0 * x2 /   2 = -t0 * x2 * SLL_CONST_1_2
     * t2 = -t1 * x2 /  12 = -t1 * x2 * SLL_CONST_1_12
     * t3 = -t2 * x2 /  30 = -t2 * x2 * SLL_CONST_1_30
     * t4 = -t3 * x2 /  56 = -t3 * x2 * SLL_CONST_1_56
     * t5 = -t4 * x2 /  90 = -t4 * x2 * SLL_CONST_1_90
     * t6 = -t5 * x2 / 132 = -t5 * x2 * SLL_CONST_1_132
     */
    retval = _sllsub(SLL_CONST_1, sllmul(x2, SLL_CONST_1_132));
    retval = _sllsub(SLL_CONST_1, sllmul(sllmul(x2, retval), SLL_CONST_1_90));
    retval = _sllsub(SLL_CONST_1, sllmul(sllmul(x2, retval), SLL_CONST_1_56));
    retval = _sllsub(SLL_CONST_1, sllmul(sllmul(x2, retval), SLL_CONST_1_30));
    retval = _sllsub(SLL_CONST_1, sllmul(sllmul(x2, retval), SLL_CONST_1_12));
    retval = _sllsub(SLL_CONST_1, slldiv2(sllmul(x2, retval)));
    return retval;
}
/*
 * Calculate sin x where -pi/4 <= x <= pi/4
 *
 * Description:
 *    sin x = x - x^3 / 3! + x^5 / 5! - ... + x^(2N+1) / (2N+1)!
 *    Note that (pi/4)^13 / 13! < 2^-32 which is the smallest possible number.
 */
static __inline__ sll _sllsin(sll x)
{
    sll retval, x2;
    x2 = sllmul(x, x);
    /*
     * sin x = t0 + t1 + t2 + t3 + t4 + t5 + t6
     *
     * f0 =  0! =  1
     * f1 =  3! =  3 *  2 * f0 =   6 * f0
     * f2 =  5! =  5 *  4 * f1 =  20 x f1
     * f3 =  7! =  7 *  6 * f2 =  42 * f2
     * f4 =  9! =  9 *  8 * f3 =  72 * f3
     * f5 = 11! = 11 * 10 * f4 = 110 * f4
     * f6 = 13! = 13 * 12 * f5 = 156 * f5
     *
     * t0 = 1
     * t1 = -t0 * x2 /   6 = -t0 * x2 * SLL_CONST_1_6
     * t2 = -t1 * x2 /  20 = -t1 * x2 * SLL_CONST_1_20
     * t3 = -t2 * x2 /  42 = -t2 * x2 * SLL_CONST_1_42
     * t4 = -t3 * x2 /  72 = -t3 * x2 * SLL_CONST_1_72
     * t5 = -t4 * x2 / 110 = -t4 * x2 * SLL_CONST_1_110
     * t6 = -t5 * x2 / 156 = -t5 * x2 * SLL_CONST_1_156
     */
    retval = _sllsub(x, sllmul(x2, SLL_CONST_1_156));
    retval = _sllsub(x, sllmul(sllmul(x2, retval), SLL_CONST_1_110));
    retval = _sllsub(x, sllmul(sllmul(x2, retval), SLL_CONST_1_72));
    retval = _sllsub(x, sllmul(sllmul(x2, retval), SLL_CONST_1_42));
    retval = _sllsub(x, sllmul(sllmul(x2, retval), SLL_CONST_1_20));
    retval = _sllsub(x, sllmul(sllmul(x2, retval), SLL_CONST_1_6));
    return retval;
}
static __inline__ sll sllcos(sll x)
{
    int i;
    sll retval;
    /* Calculate cos (x - i * pi/2), where -pi/4 <= x - i * pi/2 <= pi/4  */
    i = sll2int(_slladd(sllmul(x, SLL_CONST_2_PI), SLL_CONST_1_2));
    x = _sllsub(x, sllmul(int2sll(i), SLL_CONST_PI_2));
    switch (i & 3) {
        default:
        case 0:
            retval = _sllcos(x);
            break;
        case 1:
            retval = sllneg(_sllsin(x));
            break;
        case 2:
            retval = sllneg(_sllcos(x));
            break;
        case 3:
            retval = _sllsin(x);
            break;
    }
    return retval;
}
static __inline__ sll sllsin(sll x)
{
    int i;
    sll retval;
    /* Calculate sin (x - n * pi/2), where -pi/4 <= x - i * pi/2 <= pi/4 */
    i = sll2int(_slladd(sllmul(x, SLL_CONST_2_PI), SLL_CONST_1_2));
    x = _sllsub(x, sllmul(int2sll(i), SLL_CONST_PI_2));
    switch (i & 3) {
        default:
        case 0:
            retval = _sllsin(x);
            break;
        case 1:
            retval = _sllcos(x);
            break;
        case 2:
            retval = sllneg(_sllsin(x));
            break;
        case 3:
            retval = sllneg(_sllcos(x));
            break;
    }
    return retval;
}
static __inline__ sll slltan(sll x)
{
    int i;
    sll retval;
    i = sll2int(_slladd(sllmul(x, SLL_CONST_2_PI), SLL_CONST_1_2));
    x = _sllsub(x, sllmul(int2sll(i), SLL_CONST_PI_2));
    switch (i & 3) {
        default:
        case 0:
        case 2:
            retval = slldiv(_sllsin(x), _sllcos(x));
            break;
        case 1:
        case 3:
            retval = sllneg(slldiv(_sllcos(x), _sllsin(x)));
            break;
    }
    return retval;
}
/*
 * atan x = SUM[n=0,) (-1)^n * x^(2n + 1)/(2n + 1), |x| < 1
 *
 * Two term approximation
 *    a = x - x^3/3
 * Gives us
 *    atan x = a + ??
 * Let ?? = arctan ?
 *    atan x = a + arctan ?
 * Rearrange
 *    atan x - a = arctan ?
 * Apply tan to both sides
 *    tan (atan x - a) = tan arctan ?
 *    tan (atan x - a) = ?
 * Applying the standard formula
 *    tan (u - v) = (tan u - tan v) / (1 + tan u * tan v)
 * Gives us
 *    tan (atan x - a) = (tan atan x - tan a) / (1 + tan arctan x * tan a)
 * Let t = tan a
 *    tan (atan x - a) = (x - t) / (1 + x * t)
 * So finally
 *    arctan x = a + arctan ((tan x - t) / (1 + x * t))
 * And the typical worst case is x = 1.0 which converges in 3 iterations.
 */
static __inline__ sll _sllatan(sll x)
{
    sll a, t, retval;
    /* First iteration */
    a = sllmul(x, _sllsub(SLL_CONST_1, sllmul(x, sllmul(x, SLL_CONST_1_3))));
    retval = a;
    /* Second iteration */
    t = slldiv(_sllsin(a), _sllcos(a));
    x = slldiv(_sllsub(x, t), _slladd(SLL_CONST_1, sllmul(t, x)));
    a = sllmul(x, _sllsub(SLL_CONST_1, sllmul(x, sllmul(x, SLL_CONST_1_3))));
    retval = _slladd(retval, a);
    /* Third  iteration */
    t = slldiv(_sllsin(a), _sllcos(a));
    x = slldiv(_sllsub(x, t), _slladd(SLL_CONST_1, sllmul(t, x)));
    a = sllmul(x, _sllsub(SLL_CONST_1, sllmul(x, sllmul(x, SLL_CONST_1_3))));
    return _slladd(retval, a);
}
static __inline__ sll sllatan(sll x)
{
    sll retval;
    if (x < -sllneg(SLL_CONST_1))
        retval = sllneg(SLL_CONST_PI_2);
    else if (x > SLL_CONST_1)
        retval = SLL_CONST_PI_2;
    else
        return _sllatan(x);
    return _sllsub(retval, _sllatan(sllinv(x)));
}
/*
 * Calculate e^x where -0.5 <= x <= 0.5
 *
 * Description:
 *    e^x = x^0 / 0! + x^1 / 1! + ... + x^N / N!
 *    Note that 0.5^11 / 11! < 2^-32 which is the smallest possible number.
 */
static __inline__ sll _sllexp(sll x)
{
    sll retval;
    retval = _slladd(SLL_CONST_1, sllmul(0, sllmul(x, SLL_CONST_1_11)));
    retval = _slladd(SLL_CONST_1, sllmul(retval, sllmul(x, SLL_CONST_1_11)));
    retval = _slladd(SLL_CONST_1, sllmul(retval, sllmul(x, SLL_CONST_1_10)));
    retval = _slladd(SLL_CONST_1, sllmul(retval, sllmul(x, SLL_CONST_1_9)));
    retval = _slladd(SLL_CONST_1, sllmul(retval, slldiv2n(x, 3)));
    retval = _slladd(SLL_CONST_1, sllmul(retval, sllmul(x, SLL_CONST_1_7)));
    retval = _slladd(SLL_CONST_1, sllmul(retval, sllmul(x, SLL_CONST_1_6)));
    retval = _slladd(SLL_CONST_1, sllmul(retval, sllmul(x, SLL_CONST_1_5)));
    retval = _slladd(SLL_CONST_1, sllmul(retval, slldiv4(x)));
    retval = _slladd(SLL_CONST_1, sllmul(retval, sllmul(x, SLL_CONST_1_3)));
    retval = _slladd(SLL_CONST_1, sllmul(retval, slldiv2(x)));
    return retval;
}
/*
 * Calculate e^x where x is arbitrary
 */
static __inline__ sll sllexp(sll x)
{
    int i;
    sll e, retval;
    e = SLL_CONST_E;
    /* -0.5 <= x <= 0.5  */
    i = sll2int(_slladd(x, SLL_CONST_1_2));
    retval = _sllexp(_sllsub(x, int2sll(i)));
    /* i >= 0 */
    if (i < 0) {
        i = -i;
        e = SLL_CONST_1_E;
    }
    /* Scale the result */
    for (;i; i >>= 1) {
        if (i & 1)
            retval = sllmul(retval, e);
        e = sllmul(e, e);
    }
    return retval;
}
/*
 * Calculate natural logarithm using Netwton-Raphson method
 */
static __inline__ sll slllog(sll x)
{
    sll x1, ln = 0;
    /* Scale: e^(-1/2) <= x <= e^(1/2) */
    while (x < SLL_CONST_1_SQRTE) {
        ln = _sllsub(ln, SLL_CONST_1);
        x = sllmul(x, SLL_CONST_E);
    }
    while (x > SLL_CONST_SQRTE) {
        ln = _slladd(ln, SLL_CONST_1);
        x = sllmul(x, SLL_CONST_1_E);
    }
    /* First iteration */
    x1 = sllmul(_sllsub(x, SLL_CONST_1), slldiv2(_sllsub(x, SLL_CONST_3)));
    ln = _sllsub(ln, x1);
    x = sllmul(x, _sllexp(x1));
    /* Second iteration */
    x1 = sllmul(_sllsub(x, SLL_CONST_1), slldiv2(_sllsub(x, SLL_CONST_3)));
    ln = _sllsub(ln, x1);
    x = sllmul(x, _sllexp(x1));
    /* Third iteration */
    x1 = sllmul(_sllsub(x, SLL_CONST_1), slldiv2(_sllsub(x, SLL_CONST_3)));
    ln = _sllsub(ln, x1);
    return ln;
}
/*
 * ln x^y = y * log x
 * e^(ln x^y) = e^(y * log x)
 * x^y = e^(y * ln x)
 */
static __inline__ sll sllpow(sll x, sll y)
{
    if (y == SLL_CONST_0)
        return SLL_CONST_1;
    return sllexp(sllmul(y, slllog(x)));
}
/*
 * Consider a parabola centered on the y-axis
 *     y = a * x^2 + b
 * Has zeros (y = 0)  at
 *    a * x^2 + b = 0
 *    a * x^2 = -b
 *    x^2 = -b / a
 *    x = +- (-b / a)^(1 / 2)
 * Letting a = 1 and b = -X
 *    y = x^2 - X
 *    x = +- X^(1 / 2)
 * Which is convenient since we want to find the square root of X, and we can
 * use Newton's Method to find the zeros of any f(x)
 *    xn = x - f(x) / f'(x)
 * Applied Newton's Method to our parabola
 *    f(x) = x^2 - X
 *    xn = x - (x^2 - X) / (2 * x)
 *    xn = x - (x - X / x) / 2
 * To make this converge quickly, we scale X so that
 *    X = 4^N * z
 * Taking the roots of both sides
 *    X^(1 / 2) = (4^n * z)^(1 / 2)
 *    X^(1 / 2) = 2^n * z^(1 / 2)
 * Let N = 2^n
 *    x^(1 / 2) = N * z^(1 / 2)
 * We want this to converge to the positive root, so we must start at a point
 *    0 < start <= x^(1 / 2)
 * or
 *    x^(1/2) <= start <= infinity
 * since
 *    (1/2)^(1/2) = 0.707
 *    2^(1/2) = 1.414
 * A good choice is 1 which lies in the middle, and takes 4 iterations to
 * converge from either extreme.
 */
static __inline__ sll sllsqrt(sll x)
{
    sll n, xn;
    /* Start with a scaling factor of 1 */
    n = SLL_CONST_1;
    /* Quick solutions for the simple cases */
    if (x <= SLL_CONST_0 || x == SLL_CONST_1)
        return x;
    /* Scale x so that 0.5 <= x < 2 */
    while (x >= SLL_CONST_2) {
        x = slldiv4(x);
        n = sllmul2(n);
    }
    while (x < SLL_CONST_1_2) {
        x = sllmul4(x);
        n = slldiv2(n);
    }
    /* Simple solution if x = 4^n */
    if (x == SLL_CONST_1)
        return n;
    /* The starting point */
    xn = SLL_CONST_1;
    /* Four iterations will be enough */
    xn = _sllsub(xn, slldiv2(_sllsub(xn, slldiv(x, xn))));
    xn = _sllsub(xn, slldiv2(_sllsub(xn, slldiv(x, xn))));
    xn = _sllsub(xn, slldiv2(_sllsub(xn, slldiv(x, xn))));
    xn = _sllsub(xn, slldiv2(_sllsub(xn, slldiv(x, xn))));
    /* Scale the result */
    return sllmul(n, xn);
}
#endif
static inline sll sllatan2(sll x, sll y)
{
    register sll ret;
    register sll d=slldiv(y,x);
    if (d <= SLL_CONST_1 && d >= sllneg(SLL_CONST_1))
        ret=sllmul(SLL_CONST_ATAN_1, d);
    else
        ret=sllatan(d);
    if (x > SLL_CONST_0)
            ret= slladd(ret, SLL_CONST_PI);
    return ret;
}
#ifdef __cplusplus
}
#endif
#endif /* MATHSLL_H */