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Diffstat (limited to 'lib/msun/src/e_fmodl.c')
| -rw-r--r-- | lib/msun/src/e_fmodl.c | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/lib/msun/src/e_fmodl.c b/lib/msun/src/e_fmodl.c new file mode 100644 index 0000000..e315f76 --- /dev/null +++ b/lib/msun/src/e_fmodl.c @@ -0,0 +1,149 @@ +/* @(#)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 <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <float.h> +#include <stdint.h> + +#include "fpmath.h" +#include "math.h" +#include "math_private.h" + +#define BIAS (LDBL_MAX_EXP - 1) + +#if LDBL_MANL_SIZE > 32 +typedef uint64_t manl_t; +#else +typedef uint32_t manl_t; +#endif + +#if LDBL_MANH_SIZE > 32 +typedef uint64_t manh_t; +#else +typedef uint32_t manh_t; +#endif + +/* + * These macros add and remove an explicit integer bit in front of the + * fractional mantissa, if the architecture doesn't have such a bit by + * default already. + */ +#ifdef LDBL_IMPLICIT_NBIT +#define SET_NBIT(hx) ((hx) | (1ULL << LDBL_MANH_SIZE)) +#define HFRAC_BITS LDBL_MANH_SIZE +#else +#define SET_NBIT(hx) (hx) +#define HFRAC_BITS (LDBL_MANH_SIZE - 1) +#endif + +#define MANL_SHIFT (LDBL_MANL_SIZE - 1) + +static const long double one = 1.0, Zero[] = {0.0, -0.0,}; + +/* + * fmodl(x,y) + * Return x mod y in exact arithmetic + * Method: shift and subtract + * + * Assumptions: + * - The low part of the mantissa fits in a manl_t exactly. + * - The high part of the mantissa fits in an int64_t with enough room + * for an explicit integer bit in front of the fractional bits. + */ +long double +fmodl(long double x, long double y) +{ + union IEEEl2bits ux, uy; + int64_t hx,hz; /* We need a carry bit even if LDBL_MANH_SIZE is 32. */ + manh_t hy; + manl_t lx,ly,lz; + int ix,iy,n,sx; + + ux.e = x; + uy.e = y; + sx = ux.bits.sign; + + /* purge off exception values */ + if((uy.bits.exp|uy.bits.manh|uy.bits.manl)==0 || /* y=0 */ + (ux.bits.exp == BIAS + LDBL_MAX_EXP) || /* or x not finite */ + (uy.bits.exp == BIAS + LDBL_MAX_EXP && + ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl)!=0)) /* or y is NaN */ + return (x*y)/(x*y); + if(ux.bits.exp<=uy.bits.exp) { + if((ux.bits.exp<uy.bits.exp) || + (ux.bits.manh<=uy.bits.manh && + (ux.bits.manh<uy.bits.manh || + ux.bits.manl<uy.bits.manl))) { + return x; /* |x|<|y| return x or x-y */ + } + if(ux.bits.manh==uy.bits.manh && ux.bits.manl==uy.bits.manl) { + return Zero[sx]; /* |x|=|y| return x*0*/ + } + } + + /* determine ix = ilogb(x) */ + if(ux.bits.exp == 0) { /* subnormal x */ + ux.e *= 0x1.0p512; + ix = ux.bits.exp - (BIAS + 512); + } else { + ix = ux.bits.exp - BIAS; + } + + /* determine iy = ilogb(y) */ + if(uy.bits.exp == 0) { /* subnormal y */ + uy.e *= 0x1.0p512; + iy = uy.bits.exp - (BIAS + 512); + } else { + iy = uy.bits.exp - BIAS; + } + + /* set up {hx,lx}, {hy,ly} and align y to x */ + hx = SET_NBIT(ux.bits.manh); + hy = SET_NBIT(uy.bits.manh); + lx = ux.bits.manl; + ly = uy.bits.manl; + + /* fix point fmod */ + n = ix - iy; + + while(n--) { + hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1; + if(hz<0){hx = hx+hx+(lx>>MANL_SHIFT); lx = lx+lx;} + else { + if ((hz|lz)==0) /* return sign(x)*0 */ + return Zero[sx]; + hx = hz+hz+(lz>>MANL_SHIFT); lx = lz+lz; + } + } + hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1; + if(hz>=0) {hx=hz;lx=lz;} + + /* convert back to floating value and restore the sign */ + if((hx|lx)==0) /* return sign(x)*0 */ + return Zero[sx]; + while(hx<(1ULL<<HFRAC_BITS)) { /* normalize x */ + hx = hx+hx+(lx>>MANL_SHIFT); lx = lx+lx; + iy -= 1; + } + ux.bits.manh = hx; /* The mantissa is truncated here if needed. */ + ux.bits.manl = lx; + if (iy < LDBL_MIN_EXP) { + ux.bits.exp = iy + (BIAS + 512); + ux.e *= 0x1p-512; + } else { + ux.bits.exp = iy + BIAS; + } + x = ux.e * one; /* create necessary signal */ + return x; /* exact output */ +} |
