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authorUlrich Drepper <drepper@redhat.com>1999-07-14 00:54:57 +0000
committerUlrich Drepper <drepper@redhat.com>1999-07-14 00:54:57 +0000
commitabfbdde177c3a7155070dda1b2cdc8292054cc26 (patch)
treee021306b596381fbf8311d2b7eb294e918ff17c8 /sysdeps/ieee754/flt-32/s_expm1f.c
parent86421aa57ecfd70963ae66848bd6a6dd3b8e0fe6 (diff)
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Update.
Diffstat (limited to 'sysdeps/ieee754/flt-32/s_expm1f.c')
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diff --git a/sysdeps/ieee754/flt-32/s_expm1f.c b/sysdeps/ieee754/flt-32/s_expm1f.c
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+/* s_expm1f.c -- float version of s_expm1.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.
+ * ====================================================
+ */
+
+#if defined(LIBM_SCCS) && !defined(lint)
+static char rcsid[] = "$NetBSD: s_expm1f.c,v 1.5 1995/05/10 20:47:11 jtc Exp $";
+#endif
+
+#include "math.h"
+#include "math_private.h"
+
+static const volatile float huge = 1.0e+30, tiny = 1.0e-30;
+
+#ifdef __STDC__
+static const float
+#else
+static float
+#endif
+one		= 1.0,
+o_threshold	= 8.8721679688e+01,/* 0x42b17180 */
+ln2_hi		= 6.9313812256e-01,/* 0x3f317180 */
+ln2_lo		= 9.0580006145e-06,/* 0x3717f7d1 */
+invln2		= 1.4426950216e+00,/* 0x3fb8aa3b */
+	/* scaled coefficients related to expm1 */
+Q1  =  -3.3333335072e-02, /* 0xbd088889 */
+Q2  =   1.5873016091e-03, /* 0x3ad00d01 */
+Q3  =  -7.9365076090e-05, /* 0xb8a670cd */
+Q4  =   4.0082177293e-06, /* 0x36867e54 */
+Q5  =  -2.0109921195e-07; /* 0xb457edbb */
+
+#ifdef __STDC__
+	float __expm1f(float x)
+#else
+	float __expm1f(x)
+	float x;
+#endif
+{
+	float y,hi,lo,c,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|>=88.721... */
+                if(hx>0x7f800000)
+		    return x+x; 	 /* NaN */
+		if(hx==0x7f800000)
+		    return (xsb==0)? x:-1.0;/* exp(+-inf)={inf,-1} */
+	        if(x > o_threshold) return huge*huge; /* overflow */
+	    }
+	    if(xsb!=0) { /* x < -27*ln2, return -1.0 with inexact */
+		if(x+tiny<(float)0.0)	/* raise inexact */
+		return tiny-one;	/* return -1 */
+	    }
+	}
+
+    /* argument reduction */
+	if(hx > 0x3eb17218) {		/* if  |x| > 0.5 ln2 */ 
+	    if(hx < 0x3F851592) {	/* and |x| < 1.5 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)?(float)0.5:(float)-0.5);
+		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 = (float)0.5*x;
+	hxs = x*hfx;
+	r1 = one+hxs*(Q1+hxs*(Q2+hxs*(Q3+hxs*(Q4+hxs*Q5))));
+	t  = (float)3.0-r1*hfx;
+	e  = hxs*((r1-t)/((float)6.0 - 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 (float)0.5*(x-e)-(float)0.5;
+	    if(k==1) {
+	       	if(x < (float)-0.25) return -(float)2.0*(e-(x+(float)0.5));
+	       	else 	      return  one+(float)2.0*(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)