/* ef_pow.c -- float version of e_pow.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#include "fdlibm.h"
#include "math_config.h"

#if __OBSOLETE_MATH_FLOAT

#ifdef __v810__
#define const
#endif

static const float
bp[] = {1.0, 1.5,},
dp_h[] = { 0.0, 5.84960938e-01,}, /* 0x3f15c000 */
dp_l[] = { 0.0, 1.56322085e-06,}, /* 0x35d1cfdc */
zero    =  0.0,
one	=  1.0,
two	=  2.0,
two24	=  16777216.0,	/* 0x4b800000 */
	/* poly coefs for (3/2)*(log(x)-2s-2/3*s**3 */
L1  =  6.0000002384e-01, /* 0x3f19999a */
L2  =  4.2857143283e-01, /* 0x3edb6db7 */
L3  =  3.3333334327e-01, /* 0x3eaaaaab */
L4  =  2.7272811532e-01, /* 0x3e8ba305 */
L5  =  2.3066075146e-01, /* 0x3e6c3255 */
L6  =  2.0697501302e-01, /* 0x3e53f142 */
P1   =  1.6666667163e-01, /* 0x3e2aaaab */
P2   = -2.7777778450e-03, /* 0xbb360b61 */
P3   =  6.6137559770e-05, /* 0x388ab355 */
P4   = -1.6533901999e-06, /* 0xb5ddea0e */
P5   =  4.1381369442e-08, /* 0x3331bb4c */
lg2  =  6.9314718246e-01, /* 0x3f317218 */
lg2_h  =  6.93145752e-01, /* 0x3f317200 */
lg2_l  =  1.42860654e-06, /* 0x35bfbe8c */
ovt =  4.2995665694e-08, /* -(128-log2(ovfl+.5ulp)) */
cp    =  9.6179670095e-01, /* 0x3f76384f =2/(3ln2) */
cp_h  =  9.6179199219e-01, /* 0x3f763800 =head of cp */
cp_l  =  4.7017383622e-06, /* 0x369dc3a0 =tail of cp_h */
ivln2    =  1.4426950216e+00, /* 0x3fb8aa3b =1/ln2 */
ivln2_h  =  1.4426879883e+00, /* 0x3fb8aa00 =16b 1/ln2*/
ivln2_l  =  7.0526075433e-06; /* 0x36eca570 =1/ln2 tail*/

float
powf(float x, float y)
{
    float z, ax, z_h, z_l, p_h, p_l;
    float y1, t1, t2, r, s, t, u, v, w;
    __int32_t i, j, k, yisint, n;
    __int32_t hx, hy, ix, iy, is;

    GET_FLOAT_WORD(hx, x);
    GET_FLOAT_WORD(hy, y);
    ix = hx & 0x7fffffff;
    iy = hy & 0x7fffffff;

    /* y==zero: x**0 = 1 */
    if (FLT_UWORD_IS_ZERO(iy)) {
        if (issignalingf_inline(x))
            return x + y;
        return one;
    }

    /* x|y==NaN return NaN unless x==1 then return 1 */
    if (FLT_UWORD_IS_NAN(ix) || FLT_UWORD_IS_NAN(iy)) {
        if (hx == 0x3f800000 && !issignalingf_inline(y))
            return one;
        else
            return x + y;
    }

    /* determine if y is an odd int when x < 0
     * yisint = 0	... y is not an integer
     * yisint = 1	... y is an odd int
     * yisint = 2	... y is an even int
     */
    yisint = 0;
    if (hx < 0) {
        if (iy >= 0x4b800000)
            yisint = 2; /* even integer y */
        else if (iy >= 0x3f800000) {
            k = (iy >> 23) - 0x7f; /* exponent */
            j = iy >> (23 - k);
            if ((j << (23 - k)) == iy)
                yisint = 2 - (j & 1);
        }
    }

    /* special value of y */
    if (FLT_UWORD_IS_INFINITE(iy)) { /* y is +-inf */
        if (ix == 0x3f800000)
            return one; /* +-1**+-inf = 1 */
        else if (ix > 0x3f800000) /* (|x|>1)**+-inf = inf,0 */
            return (hy >= 0) ? y : zero;
        else /* (|x|<1)**-,+inf = inf,0 */
            return (hy < 0) ? -y : zero;
    }
    if (iy == 0x3f800000) { /* y is  +-1 */
        if (hy < 0) {
            if (x == 0)
                return __math_divzerof(hx < 0);
            return one / x;
        } else
            return x;
    }
    if (hy == 0x40000000 && ix < 0x5f800000 && ix > 0x1a000000)
        return x * x; /* y is  2 */
    if (hy == 0x3f000000) { /* y is  0.5 */
        if (hx >= 0) /* x >= +0 */
            return sqrtf(x);
    }

    ax = fabsf(x);
    /* special value of x */
    if (FLT_UWORD_IS_INFINITE(ix) || ix == 0x3f800000) {
        z = ax; /*x is +-inf,+-1*/
        if (hy < 0)
            z = one / z; /* z = (1/|x|) */
        if (hx < 0) {
            if (((ix - 0x3f800000) | yisint) == 0) {
                return __math_invalidf(x); /* (-1)**non-int is NaN */
            } else if (yisint == 1)
                z = -z; /* (x<0)**odd = -(|x|**odd) */
        }
        return z;
    }

    if (FLT_UWORD_IS_ZERO(ix)) {
        if (hy < 0)
            return __math_divzerof(hx < 0 && yisint == 1);
        if (yisint != 1)
            x = ax;
        return x;
    }

    /* (x<0)**(non-int) is NaN */
    if (((((__uint32_t)hx >> 31) - 1) | yisint) == 0)
        return __math_invalidf(x);

    /* |y| is huge */
    if (iy > 0x4d000000) { /* if |y| > 2**27 */
        /* over/underflow if x is not close to one */
        if (ix < 0x3f7ffff4)
            return (hy < 0) ? __math_oflowf(0) : __math_uflowf(0);
        if (ix > 0x3f800007)
            return (hy > 0) ? __math_oflowf(0) : __math_uflowf(0);
        /* now |1-x| is tiny <= 2**-20, suffice to compute
	   log(x) by x-x^2/2+x^3/3-x^4/4 */
        t = ax - 1; /* t has 20 trailing zeros */
        w = (t * t) *
            ((float)0.5 - t * ((float)0.333333333333 - t * (float)0.25));
        u = ivln2_h * t; /* ivln2_h has 16 sig. bits */
        v = t * ivln2_l - w * ivln2;
        t1 = u + v;
        GET_FLOAT_WORD(is, t1);
        SET_FLOAT_WORD(t1, is & 0xfffff000);
        t2 = v - (t1 - u);
    } else {
        float s2, s_h, s_l, t_h, t_l;
        n = 0;
        /* take care subnormal number */
        if (FLT_UWORD_IS_SUBNORMAL(ix)) {
            ax *= two24;
            n -= 24;
            GET_FLOAT_WORD(ix, ax);
        }
        n += ((ix) >> 23) - 0x7f;
        j = ix & 0x007fffff;
        /* determine interval */
        ix = j | 0x3f800000; /* normalize ix */
        if (j <= 0x1cc471)
            k = 0; /* |x|<sqrt(3/2) */
        else if (j < 0x5db3d7)
            k = 1; /* |x|<sqrt(3)   */
        else {
            k = 0;
            n += 1;
            ix -= 0x00800000;
        }
        SET_FLOAT_WORD(ax, ix);

        /* compute s = s_h+s_l = (x-1)/(x+1) or (x-1.5)/(x+1.5) */
        u = ax - bp[k]; /* bp[0]=1.0, bp[1]=1.5 */
        v = one / (ax + bp[k]);
        s = u * v;
        s_h = s;
        GET_FLOAT_WORD(is, s_h);
        SET_FLOAT_WORD(s_h, is & 0xfffff000);
        /* t_h=ax+bp[k] High */
        SET_FLOAT_WORD(t_h, ((ix >> 1) | 0x20000000) + 0x0040000 + (k << 21));
        t_l = ax - (t_h - bp[k]);
        s_l = v * ((u - s_h * t_h) - s_h * t_l);
        /* compute log(ax) */
        s2 = s * s;
        r = s2 * s2 *
            (L1 + s2 * (L2 + s2 * (L3 + s2 * (L4 + s2 * (L5 + s2 * L6)))));
        r += s_l * (s_h + s);
        s2 = s_h * s_h;
        t_h = (float)3.0 + s2 + r;
        GET_FLOAT_WORD(is, t_h);
        SET_FLOAT_WORD(t_h, is & 0xfffff000);
        t_l = r - ((t_h - (float)3.0) - s2);
        /* u+v = s*(1+...) */
        u = s_h * t_h;
        v = s_l * t_h + t_l * s;
        /* 2/(3log2)*(s+...) */
        p_h = u + v;
        GET_FLOAT_WORD(is, p_h);
        SET_FLOAT_WORD(p_h, is & 0xfffff000);
        p_l = v - (p_h - u);
        z_h = cp_h * p_h; /* cp_h+cp_l = 2/(3*log2) */
        z_l = cp_l * p_h + p_l * cp + dp_l[k];
        /* log2(ax) = (s+..)*2/(3*log2) = n + dp_h + z_h + z_l */
        t = (float)n;
        t1 = (((z_h + z_l) + dp_h[k]) + t);
        GET_FLOAT_WORD(is, t1);
        SET_FLOAT_WORD(t1, is & 0xfffff000);
        t2 = z_l - (((t1 - t) - dp_h[k]) - z_h);
    }

    s = one; /* s (sign of result -ve**odd) = -1 else = 1 */
    if (((((__uint32_t)hx >> 31) - 1) | (yisint - 1)) == 0)
        s = -one; /* (-ve)**(odd int) */

    /* split up y into y1+y2 and compute (y1+y2)*(t1+t2) */
    GET_FLOAT_WORD(is, y);
    SET_FLOAT_WORD(y1, is & 0xfffff000);
    p_l = (y - y1) * t1 + y * t2;
    p_h = y1 * t1;
    z = p_l + p_h;
    GET_FLOAT_WORD(j, z);
    i = j & 0x7fffffff;
    if (j > 0) {
        if (i > FLT_UWORD_EXP_MAX)
            return __math_oflowf(s < 0); /* overflow */
        else if (i == FLT_UWORD_EXP_MAX)
            if (p_l + ovt > z - p_h)
                return __math_oflowf(s < 0); /* overflow */
    } else {
        if (i > FLT_UWORD_EXP_MIN)
            return __math_uflowf(s < 0); /* underflow */
        else if (i == FLT_UWORD_EXP_MIN)
            if (p_l <= z - p_h)
                return __math_uflowf(s < 0); /* underflow */
    }
    /*
     * compute 2**(p_h+p_l)
     */
    k = (i >> 23) - 0x7f;
    n = 0;
    if (i > 0x3f000000) { /* if |z| > 0.5, set n = [z+0.5] */
        n = j + (0x00800000 >> (k + 1));
        k = ((n & 0x7fffffff) >> 23) - 0x7f; /* new k for n */
        SET_FLOAT_WORD(t, n & ~(0x007fffff >> k));
        n = ((n & 0x007fffff) | 0x00800000) >> (23 - k);
        if (j < 0)
            n = -n;
        p_h -= t;
    }
    t = p_l + p_h;
    GET_FLOAT_WORD(is, t);
    SET_FLOAT_WORD(t, is & 0xfffff000);
    u = t * lg2_h;
    v = (p_l - (t - p_h)) * lg2 + t * lg2_l;
    z = u + v;
    w = v - (z - u);
    t = z * z;
    t1 = z - t * (P1 + t * (P2 + t * (P3 + t * (P4 + t * P5))));
    r = (z * t1) / (t1 - two) - (w + z * w);
    z = one - (r - z);
    GET_FLOAT_WORD(j, z);
    j += (n << 23);
    if ((j >> 23) <= 0)
        z = scalbnf(z, (int)n); /* subnormal output */
    else
        SET_FLOAT_WORD(z, j);
    return s * z;
}

#if defined(_HAVE_ALIAS_ATTRIBUTE)
#ifndef __clang__
#pragma GCC diagnostic ignored "-Wmissing-attributes"
#endif
__strong_reference(powf, _powf);
#endif

_MATH_ALIAS_f_ff(pow)

#else
#include "../common/sf_pow.c"
#endif /* __OBSOLETE_MATH_FLOAT */
