1 /* @(#)e_fmod.c 1.3 95/01/18 */
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 * Developed at SunSoft, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
10 * ====================================================
13 #include <sys/cdefs.h>
19 #include "math_private.h"
21 #define BIAS (LDBL_MAX_EXP - 1)
23 #if LDBL_MANL_SIZE > 32
24 typedef uint64_t manl_t;
26 typedef uint32_t manl_t;
29 #if LDBL_MANH_SIZE > 32
30 typedef uint64_t manh_t;
32 typedef uint32_t manh_t;
36 * These macros add and remove an explicit integer bit in front of the
37 * fractional mantissa, if the architecture doesn't have such a bit by
40 #ifdef LDBL_IMPLICIT_NBIT
41 #define SET_NBIT(hx) ((hx) | (1ULL << LDBL_MANH_SIZE))
42 #define HFRAC_BITS LDBL_MANH_SIZE
44 #define SET_NBIT(hx) (hx)
45 #define HFRAC_BITS (LDBL_MANH_SIZE - 1)
48 #define MANL_SHIFT (LDBL_MANL_SIZE - 1)
50 static const long double Zero[] = {0.0L, -0.0L};
53 * Return the IEEE remainder and set *quo to the last n bits of the
54 * quotient, rounded to the nearest integer. We choose n=31 because
55 * we wind up computing all the integer bits of the quotient anyway as
56 * a side-effect of computing the remainder by the shift and subtract
57 * method. In practice, this is far more bits than are needed to use
58 * remquo in reduction algorithms.
61 * - The low part of the mantissa fits in a manl_t exactly.
62 * - The high part of the mantissa fits in an int64_t with enough room
63 * for an explicit integer bit in front of the fractional bits.
66 remquol(long double x, long double y, int *quo)
68 union IEEEl2bits ux, uy;
69 int64_t hx,hz; /* We need a carry bit even if LDBL_MANH_SIZE is 32. */
77 sxy = sx ^ uy.bits.sign;
78 ux.bits.sign = 0; /* |x| */
79 uy.bits.sign = 0; /* |y| */
81 /* purge off exception values */
82 if((uy.bits.exp|uy.bits.manh|uy.bits.manl)==0 || /* y=0 */
83 (ux.bits.exp == BIAS + LDBL_MAX_EXP) || /* or x not finite */
84 (uy.bits.exp == BIAS + LDBL_MAX_EXP &&
85 ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl)!=0)) /* or y is NaN */
86 return nan_mix_op(x, y, *)/nan_mix_op(x, y, *);
87 if(ux.bits.exp<=uy.bits.exp) {
88 if((ux.bits.exp<uy.bits.exp) ||
89 (ux.bits.manh<=uy.bits.manh &&
90 (ux.bits.manh<uy.bits.manh ||
91 ux.bits.manl<uy.bits.manl))) {
93 goto fixup; /* |x|<|y| return x or x-y */
95 if(ux.bits.manh==uy.bits.manh && ux.bits.manl==uy.bits.manl) {
96 *quo = (sxy ? -1 : 1);
97 return Zero[sx]; /* |x|=|y| return x*0*/
101 /* determine ix = ilogb(x) */
102 if(ux.bits.exp == 0) { /* subnormal x */
104 ix = ux.bits.exp - (BIAS + 512);
106 ix = ux.bits.exp - BIAS;
109 /* determine iy = ilogb(y) */
110 if(uy.bits.exp == 0) { /* subnormal y */
112 iy = uy.bits.exp - (BIAS + 512);
114 iy = uy.bits.exp - BIAS;
117 /* set up {hx,lx}, {hy,ly} and align y to x */
118 hx = SET_NBIT(ux.bits.manh);
119 hy = SET_NBIT(uy.bits.manh);
127 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
128 if(hz<0){hx = hx+hx+(lx>>MANL_SHIFT); lx = lx+lx;}
129 else {hx = hz+hz+(lz>>MANL_SHIFT); lx = lz+lz; q++;}
132 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
133 if(hz>=0) {hx=hz;lx=lz;q++;}
135 /* convert back to floating value and restore the sign */
136 if((hx|lx)==0) { /* return sign(x)*0 */
138 *quo = (sxy ? -q : q);
141 while(hx<(1ULL<<HFRAC_BITS)) { /* normalize x */
142 hx = hx+hx+(lx>>MANL_SHIFT); lx = lx+lx;
145 ux.bits.manh = hx; /* The integer bit is truncated here if needed. */
147 if (iy < LDBL_MIN_EXP) {
148 ux.bits.exp = iy + (BIAS + 512);
151 ux.bits.exp = iy + BIAS;
156 if (y < LDBL_MIN * 2) {
157 if (x+x>y || (x+x==y && (q & 1))) {
161 } else if (x>0.5*y || (x==0.5*y && (q & 1))) {
169 *quo = (sxy ? -q : q);