1 /* k_rem_pio2f.c -- float version of k_rem_pio2.c
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
13 * ====================================================
17 static char rcsid[] = "$Id$";
21 #include "math_private.h"
23 /* In the float version, the input parameter x contains 8 bit
24 integers, not 24 bit integers. 113 bit precision is not supported. */
27 static const int init_jk[] = {4,7,9}; /* initial value for jk */
29 static int init_jk[] = {4,7,9};
33 static const float PIo2[] = {
35 static float PIo2[] = {
37 1.5703125000e+00, /* 0x3fc90000 */
38 4.5776367188e-04, /* 0x39f00000 */
39 2.5987625122e-05, /* 0x37da0000 */
40 7.5437128544e-08, /* 0x33a20000 */
41 6.0026650317e-11, /* 0x2e840000 */
42 7.3896444519e-13, /* 0x2b500000 */
43 5.3845816694e-15, /* 0x27c20000 */
44 5.6378512969e-18, /* 0x22d00000 */
45 8.3009228831e-20, /* 0x1fc40000 */
46 3.2756352257e-22, /* 0x1bc60000 */
47 6.3331015649e-25, /* 0x17440000 */
57 two8 = 2.5600000000e+02, /* 0x43800000 */
58 twon8 = 3.9062500000e-03; /* 0x3b800000 */
61 int __kernel_rem_pio2f(float *x, float *y, int e0, int nx, int prec, const int32_t *ipio2)
63 int __kernel_rem_pio2f(x,y,e0,nx,prec,ipio2)
64 float x[], y[]; int e0,nx,prec; int32_t ipio2[];
67 int32_t jz,jx,jv,jp,jk,carry,n,iq[20],i,j,k,m,q0,ih;
68 float z,fw,f[20],fq[20],q[20];
74 /* determine jx,jv,q0, note that 3>q0 */
76 jv = (e0-3)/8; if(jv<0) jv=0;
79 /* set up f[0] to f[jx+jk] where f[jx+jk] = ipio2[jv+jk] */
81 for(i=0;i<=m;i++,j++) f[i] = (j<0)? zero : (float) ipio2[j];
83 /* compute q[0],q[1],...q[jk] */
85 for(j=0,fw=0.0;j<=jx;j++) fw += x[j]*f[jx+i-j]; q[i] = fw;
90 /* distill q[] into iq[] reversingly */
91 for(i=0,j=jz,z=q[jz];j>0;i++,j--) {
92 fw = (float)((int32_t)(twon8* z));
93 iq[i] = (int32_t)(z-two8*fw);
98 z = scalbnf(z,q0); /* actual value of z */
99 z -= (float)8.0*floorf(z*(float)0.125); /* trim off integer >= 8 */
103 if(q0>0) { /* need iq[jz-1] to determine n */
104 i = (iq[jz-1]>>(8-q0)); n += i;
105 iq[jz-1] -= i<<(8-q0);
106 ih = iq[jz-1]>>(7-q0);
108 else if(q0==0) ih = iq[jz-1]>>8;
109 else if(z>=(float)0.5) ih=2;
111 if(ih>0) { /* q > 0.5 */
113 for(i=0;i<jz ;i++) { /* compute 1-q */
117 carry = 1; iq[i] = 0x100- j;
119 } else iq[i] = 0xff - j;
121 if(q0>0) { /* rare case: chance is 1 in 12 */
124 iq[jz-1] &= 0x7f; break;
126 iq[jz-1] &= 0x3f; break;
131 if(carry!=0) z -= scalbnf(one,q0);
135 /* check if recomputation is needed */
138 for (i=jz-1;i>=jk;i--) j |= iq[i];
139 if(j==0) { /* need recomputation */
140 for(k=1;iq[jk-k]==0;k++); /* k = no. of terms needed */
142 for(i=jz+1;i<=jz+k;i++) { /* add q[jz+1] to q[jz+k] */
143 f[jx+i] = (float) ipio2[jv+i];
144 for(j=0,fw=0.0;j<=jx;j++) fw += x[j]*f[jx+i-j];
152 /* chop off zero terms */
155 while(iq[jz]==0) { jz--; q0-=8;}
156 } else { /* break z into 8-bit if necessary */
159 fw = (float)((int32_t)(twon8*z));
160 iq[jz] = (int32_t)(z-two8*fw);
162 iq[jz] = (int32_t) fw;
163 } else iq[jz] = (int32_t) z ;
166 /* convert integer "bit" chunk to floating-point value */
167 fw = scalbnf(one,q0);
169 q[i] = fw*(float)iq[i]; fw*=twon8;
172 /* compute PIo2[0,...,jp]*q[jz,...,0] */
174 for(fw=0.0,k=0;k<=jp&&k<=jz-i;k++) fw += PIo2[k]*q[i+k];
178 /* compress fq[] into y[] */
182 for (i=jz;i>=0;i--) fw += fq[i];
183 y[0] = (ih==0)? fw: -fw;
188 for (i=jz;i>=0;i--) fw += fq[i];
189 y[0] = (ih==0)? fw: -fw;
191 for (i=1;i<=jz;i++) fw += fq[i];
192 y[1] = (ih==0)? fw: -fw;
194 case 3: /* painful */
205 for (fw=0.0,i=jz;i>=2;i--) fw += fq[i];
207 y[0] = fq[0]; y[1] = fq[1]; y[2] = fw;
209 y[0] = -fq[0]; y[1] = -fq[1]; y[2] = -fw;