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/* 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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/* |
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* 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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static const float one = 1.0, Zero[] = {0.0, -0.0,}; |
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float |
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fmodf(float x, float y) |
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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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DEF_STD(fmodf); |