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[/] [openrisc/] [trunk/] [gnu-stable/] [newlib-1.18.0/] [newlib/] [libm/] [common/] [sf_remquo.c] - Rev 207
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/* Adapted for Newlib, 2009. (Allow for int < 32 bits; return *quo=0 during * errors to make test scripts easier.) */ /* @(#)e_fmod.c 1.3 95/01/18 */ /*- * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunSoft, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== */ #include <math.h> #include "fdlibm.h" /* For quotient, return either all 31 bits that can from calculation (using * int32_t), or as many as can fit into an int that is smaller than 32 bits. */ #if INT_MAX > 0x7FFFFFFFL #define QUO_MASK 0x7FFFFFFF # else #define QUO_MASK INT_MAX #endif static const float Zero[] = {0.0, -0.0,}; /* * Return the IEEE remainder and set *quo to the last n bits of the * quotient, rounded to the nearest integer. We choose n=31--if that many fit-- * we wind up computing all the integer bits of the quotient anyway as * a side-effect of computing the remainder by the shift and subtract * method. In practice, this is far more bits than are needed to use * remquo in reduction algorithms. */ float remquof(float x, float y, int *quo) { __int32_t n,hx,hy,hz,ix,iy,sx,i; __uint32_t q,sxy; GET_FLOAT_WORD(hx,x); GET_FLOAT_WORD(hy,y); sxy = (hx ^ hy) & 0x80000000; sx = hx&0x80000000; /* sign of x */ hx ^=sx; /* |x| */ hy &= 0x7fffffff; /* |y| */ /* purge off exception values */ if(hy==0||hx>=0x7f800000||hy>0x7f800000) { /* y=0,NaN;or x not finite */ *quo = 0; /* Not necessary, but return consistent value */ return (x*y)/(x*y); } if(hx<hy) { q = 0; goto fixup; /* |x|<|y| return x or x-y */ } else if(hx==hy) { *quo = 1; return Zero[(__uint32_t)sx>>31]; /* |x|=|y| return x*0*/ } /* determine ix = ilogb(x) */ if(hx<0x00800000) { /* subnormal x */ for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; } else ix = (hx>>23)-127; /* determine iy = ilogb(y) */ if(hy<0x00800000) { /* subnormal y */ for (iy = -126,i=(hy<<8); i>0; i<<=1) iy -=1; } else iy = (hy>>23)-127; /* set up {hx,lx}, {hy,ly} and align y to x */ if(ix >= -126) hx = 0x00800000|(0x007fffff&hx); else { /* subnormal x, shift x to normal */ n = -126-ix; hx <<= n; } if(iy >= -126) hy = 0x00800000|(0x007fffff&hy); else { /* subnormal y, shift y to normal */ n = -126-iy; hy <<= n; } /* fix point fmod */ n = ix - iy; q = 0; while(n--) { hz=hx-hy; if(hz<0) hx = hx << 1; else {hx = hz << 1; q++;} q <<= 1; } hz=hx-hy; if(hz>=0) {hx=hz;q++;} /* convert back to floating value and restore the sign */ if(hx==0) { /* return sign(x)*0 */ *quo = (sxy ? -q : q); return Zero[(__uint32_t)sx>>31]; } while(hx<0x00800000) { /* normalize x */ hx <<= 1; iy -= 1; } if(iy>= -126) { /* normalize output */ hx = ((hx-0x00800000)|((iy+127)<<23)); } else { /* subnormal output */ n = -126 - iy; hx >>= n; } fixup: SET_FLOAT_WORD(x,hx); y = fabsf(y); if (y < 0x1p-125f) { if (x+x>y || (x+x==y && (q & 1))) { q++; x-=y; } } else if (x>0.5f*y || (x==0.5f*y && (q & 1))) { q++; x-=y; } GET_FLOAT_WORD(hx,x); SET_FLOAT_WORD(x,hx^sx); q &= 0x7fffffff; *quo = (sxy ? -q : q); return x; }
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