/* See the import.pl script for potential modifications */
/* s_expm1f.c -- Simple version of s_expm1.c.
 * Conversion to Simple 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.
  * ====================================================
  */

#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: s_expm1f.c,v 1.5f 1995/05/10 20:47:11 jtc Exp $";
#endif

#include "SMath.h"
#include "math_private.h"

static const Simple huge = 1.0e+30f;
static const Simple tiny = 1.0e-30f;

namespace streflop_libm {
#ifdef __STDC__
	static const Simple
#else
	static Simple
#endif
		one = 1.0f,
		o_threshold = 8.8721679688e+01f,/* 0x42b17180 */
		ln2_hi = 6.9313812256e-01f,/* 0x3f317180 */
		ln2_lo = 9.0580006145e-06f,/* 0x3717f7d1 */
		invln2 = 1.4426950216e+00f,/* 0x3fb8aa3b */
			/* scaled coefficients related to expm1 */
		Q1 = -3.3333335072e-02f, /* 0xbd088889 */
		Q2 = 1.5873016091e-03f, /* 0x3ad00d01 */
		Q3 = -7.9365076090e-05f, /* 0xb8a670cd */
		Q4 = 4.0082177293e-06f, /* 0x36867e54 */
		Q5 = -2.0109921195e-07f; /* 0xb457edbb */

#ifdef __STDC__
	Simple __expm1f(Simple x)
#else
	Simple __expm1f(x)
		Simple x;
#endif
	{
		Simple y, hi, lo, c = 0, t, e, hxs, hfx, r1;
		int32_t k, xsb;
		u_int32_t hx;

		GET_FLOAT_WORD(hx, x);
		xsb = hx & 0x80000000;		/* sign bit of x */
		if (xsb == 0) y = x; else y = -x;	/* y = |x| */
		hx &= 0x7fffffff;		/* high word of |x| */

		/* filter out huge and non-finite argument */
		if (hx >= 0x4195b844) {			/* if |x|>=27*ln2 */
			if (hx >= 0x42b17218) {		/* if |x|>=88.721f... */
				if (hx > 0x7f800000)
					return x + x; 	 /* NaN */
				if (hx == 0x7f800000)
					return (xsb == 0) ? x : -Simple(1.0f);/* exp(+-inf)={inf,-1} */
				if (x > o_threshold) return huge*huge; /* overflow */
			}
			if (xsb != 0) { /* x < -27*ln2, return -1.0f with inexact */
				if (x + tiny < (Simple)0.0f)	/* raise inexact */
					return tiny - one;	/* return -1 */
			}
		}

		/* argument reduction */
		if (hx > 0x3eb17218) {		/* if  |x| > 0.5f ln2 */
			if (hx < 0x3F851592) {	/* and |x| < 1.5f ln2 */
				if (xsb == 0) {
					hi = x - ln2_hi; lo = ln2_lo;  k = 1;
				} else {
					hi = x + ln2_hi; lo = -ln2_lo;  k = -1;
				}
			} else {
				k = invln2*x + ((xsb == 0) ? (Simple)0.5f : (Simple) -0.5f);
				t = k;
				hi = x - t*ln2_hi;	/* t*ln2_hi is exact here */
				lo = t*ln2_lo;
			}
			x = hi - lo;
			c = (hi - x) - lo;
		} else if (hx < 0x33000000) {  	/* when |x|<2**-25, return x */
			t = huge + x;	/* return x with inexact flags when x!=0 */
			return x - (t - (huge + x));
		} else k = 0;

		/* x is now in primary range */
		hfx = (Simple)0.5f*x;
		hxs = x*hfx;
		r1 = one + hxs*(Q1 + hxs*(Q2 + hxs*(Q3 + hxs*(Q4 + hxs*Q5))));
		t = (Simple)3.0f - r1*hfx;
		e = hxs*((r1 - t) / ((Simple)6.0f - x*t));
		if (k == 0) return x - (x*e - hxs);		/* c is 0 */
		else {
			e = (x*(e - c) - c);
			e -= hxs;
			if (k == -1) return (Simple)0.5f*(x - e) - (Simple)0.5f;
			if (k == 1) {
				if (x < (Simple) -0.25f) return -(Simple)2.0f*(e - (x + (Simple)0.5f));
				else 	      return  one + (Simple)2.0f*(x - e);
			}
			if (k <= -2 || k > 56) {   /* suffice to return exp(x)-1 */
				int32_t i;
				y = one - (e - x);
				GET_FLOAT_WORD(i, y);
				SET_FLOAT_WORD(y, i + (k << 23));	/* add k to y's exponent */
				return y - one;
			}
			t = one;
			if (k < 23) {
				int32_t i;
				SET_FLOAT_WORD(t, 0x3f800000 - (0x1000000 >> k)); /* t=1-2^-k */
				y = t - (e - x);
				GET_FLOAT_WORD(i, y);
				SET_FLOAT_WORD(y, i + (k << 23));	/* add k to y's exponent */
			} else {
				int32_t i;
				SET_FLOAT_WORD(t, ((0x7f - k) << 23));	/* 2^-k */
				y = x - (e + t);
				y += one;
				GET_FLOAT_WORD(i, y);
				SET_FLOAT_WORD(y, i + (k << 23));	/* add k to y's exponent */
			}
		}
		return y;
	}
	weak_alias(__expm1f, expm1f)
}
