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Diffstat (limited to 'src/math/fmodl.c')
| -rw-r--r-- | src/math/fmodl.c | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/src/math/fmodl.c b/src/math/fmodl.c new file mode 100644 index 00000000..2e3eec1f --- /dev/null +++ b/src/math/fmodl.c @@ -0,0 +1,159 @@ +/* origin: FreeBSD /usr/src/lib/msun/src/e_fmodl.c */ +/*- + * ==================================================== + * 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 "libm.h" + +#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024 +long double fmodl(long double x, long double y) +{ + return fmod(x, y); +} +#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384 + +#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))) /* |x|<|y| return x or x-y */ + return x; + 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 */ +} +#endif |