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3a8617a83f
-- Begin comments from J.T. Conklin: The most significant improvement is the addition of "float" versions of the math functions that take float arguments, return floats, and do all operations in floating point. This doesn't help (performance) much on the i386, but they are still nice to have. The float versions were orginally done by Cygnus' Ian Taylor when fdlibm was integrated into the libm we support for embedded systems. I gave Ian a copy of my libm as a starting point since I had already fixed a lot of bugs & problems in Sun's original code. After he was done, I cleaned it up a bit and integrated the changes back into my libm. -- End comments Reviewed by: jkh Submitted by: jtc
113 lines
2.8 KiB
C
113 lines
2.8 KiB
C
/* e_fmodf.c -- float version of e_fmod.c.
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* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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*/
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#ifndef lint
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static char rcsid[] = "$Id: e_fmodf.c,v 1.2 1994/08/18 23:05:23 jtc Exp $";
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#endif
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/*
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* __ieee754_fmodf(x,y)
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* Return x mod y in exact arithmetic
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* Method: shift and subtract
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*/
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#include "math.h"
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#include "math_private.h"
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#ifdef __STDC__
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static const float one = 1.0, Zero[] = {0.0, -0.0,};
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#else
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static float one = 1.0, Zero[] = {0.0, -0.0,};
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#endif
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#ifdef __STDC__
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float __ieee754_fmodf(float x, float y)
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#else
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float __ieee754_fmodf(x,y)
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float x,y ;
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#endif
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{
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int32_t n,hx,hy,hz,ix,iy,sx,i;
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GET_FLOAT_WORD(hx,x);
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GET_FLOAT_WORD(hy,y);
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sx = hx&0x80000000; /* sign of x */
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hx ^=sx; /* |x| */
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hy &= 0x7fffffff; /* |y| */
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/* purge off exception values */
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if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */
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(hy>0x7f800000)) /* or y is NaN */
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return (x*y)/(x*y);
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if(hx<hy) return x; /* |x|<|y| return x */
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if(hx==hy)
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return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/
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/* determine ix = ilogb(x) */
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if(hx<0x00800000) { /* subnormal x */
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for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
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} else ix = (hx>>23)-127;
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/* determine iy = ilogb(y) */
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if(hy<0x00800000) { /* subnormal y */
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for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1;
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} else iy = (hy>>23)-127;
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/* set up {hx,lx}, {hy,ly} and align y to x */
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if(ix >= -126)
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hx = 0x00800000|(0x007fffff&hx);
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else { /* subnormal x, shift x to normal */
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n = -126-ix;
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hx = hx<<n;
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}
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if(iy >= -126)
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hy = 0x00800000|(0x007fffff&hy);
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else { /* subnormal y, shift y to normal */
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n = -126-iy;
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hy = hy<<n;
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}
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/* fix point fmod */
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n = ix - iy;
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while(n--) {
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hz=hx-hy;
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if(hz<0){hx = hx+hx;}
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else {
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if(hz==0) /* return sign(x)*0 */
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return Zero[(u_int32_t)sx>>31];
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hx = hz+hz;
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}
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}
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hz=hx-hy;
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if(hz>=0) {hx=hz;}
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/* convert back to floating value and restore the sign */
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if(hx==0) /* return sign(x)*0 */
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return Zero[(u_int32_t)sx>>31];
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while(hx<0x00800000) { /* normalize x */
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hx = hx+hx;
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iy -= 1;
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}
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if(iy>= -126) { /* normalize output */
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hx = ((hx-0x00800000)|((iy+127)<<23));
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SET_FLOAT_WORD(x,hx|sx);
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} else { /* subnormal output */
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n = -126 - iy;
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hx >>= n;
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SET_FLOAT_WORD(x,hx|sx);
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x *= one; /* create necessary signal */
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}
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return x; /* exact output */
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}
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