diff options
Diffstat (limited to 'sysdeps/libm-ieee754/e_pow.c')
| -rw-r--r-- | sysdeps/libm-ieee754/e_pow.c | 160 |
1 files changed, 102 insertions, 58 deletions
diff --git a/sysdeps/libm-ieee754/e_pow.c b/sysdeps/libm-ieee754/e_pow.c index 4b9ba3d5eb..02b16c5171 100644 --- a/sysdeps/libm-ieee754/e_pow.c +++ b/sysdeps/libm-ieee754/e_pow.c @@ -9,6 +9,9 @@ * is preserved. * ==================================================== */ +/* Modified by Naohiko Shimizu/Tokai University, Japan 1997/08/25, + for performance improvement on pipelined processors. +*/ #if defined(LIBM_SCCS) && !defined(lint) static char rcsid[] = "$NetBSD: e_pow.c,v 1.9 1995/05/12 04:57:32 jtc Exp $"; @@ -61,6 +64,33 @@ static char rcsid[] = "$NetBSD: e_pow.c,v 1.9 1995/05/12 04:57:32 jtc Exp $"; #include "math.h" #include "math_private.h" +#define zero C[0] +#define one C[1] +#define two C[2] +#define two53 C[3] +#define huge C[4] +#define tiny C[5] +#define L1 C[6] +#define L2 C[7] +#define L3 C[8] +#define L4 C[9] +#define L5 C[10] +#define L6 C[11] +#define P1 C[12] +#define P2 C[13] +#define P3 C[14] +#define P4 C[15] +#define P5 C[16] +#define lg2 C[17] +#define lg2_h C[18] +#define lg2_l C[19] +#define ovt C[20] +#define cp C[21] +#define cp_h C[22] +#define cp_l C[23] +#define ivln2 C[24] +#define ivln2_h C[25] +#define ivln2_l C[26] #ifdef __STDC__ static const double @@ -70,34 +100,34 @@ static double bp[] = {1.0, 1.5,}, dp_h[] = { 0.0, 5.84962487220764160156e-01,}, /* 0x3FE2B803, 0x40000000 */ dp_l[] = { 0.0, 1.35003920212974897128e-08,}, /* 0x3E4CFDEB, 0x43CFD006 */ -zero = 0.0, -one = 1.0, -two = 2.0, -two53 = 9007199254740992.0, /* 0x43400000, 0x00000000 */ -huge = 1.0e300, -tiny = 1.0e-300, - /* poly coefs for (3/2)*(log(x)-2s-2/3*s**3 */ -L1 = 5.99999999999994648725e-01, /* 0x3FE33333, 0x33333303 */ -L2 = 4.28571428578550184252e-01, /* 0x3FDB6DB6, 0xDB6FABFF */ -L3 = 3.33333329818377432918e-01, /* 0x3FD55555, 0x518F264D */ -L4 = 2.72728123808534006489e-01, /* 0x3FD17460, 0xA91D4101 */ -L5 = 2.30660745775561754067e-01, /* 0x3FCD864A, 0x93C9DB65 */ -L6 = 2.06975017800338417784e-01, /* 0x3FCA7E28, 0x4A454EEF */ -P1 = 1.66666666666666019037e-01, /* 0x3FC55555, 0x5555553E */ -P2 = -2.77777777770155933842e-03, /* 0xBF66C16C, 0x16BEBD93 */ -P3 = 6.61375632143793436117e-05, /* 0x3F11566A, 0xAF25DE2C */ -P4 = -1.65339022054652515390e-06, /* 0xBEBBBD41, 0xC5D26BF1 */ -P5 = 4.13813679705723846039e-08, /* 0x3E663769, 0x72BEA4D0 */ -lg2 = 6.93147180559945286227e-01, /* 0x3FE62E42, 0xFEFA39EF */ -lg2_h = 6.93147182464599609375e-01, /* 0x3FE62E43, 0x00000000 */ -lg2_l = -1.90465429995776804525e-09, /* 0xBE205C61, 0x0CA86C39 */ -ovt = 8.0085662595372944372e-0017, /* -(1024-log2(ovfl+.5ulp)) */ -cp = 9.61796693925975554329e-01, /* 0x3FEEC709, 0xDC3A03FD =2/(3ln2) */ -cp_h = 9.61796700954437255859e-01, /* 0x3FEEC709, 0xE0000000 =(float)cp */ -cp_l = -7.02846165095275826516e-09, /* 0xBE3E2FE0, 0x145B01F5 =tail of cp_h*/ -ivln2 = 1.44269504088896338700e+00, /* 0x3FF71547, 0x652B82FE =1/ln2 */ -ivln2_h = 1.44269502162933349609e+00, /* 0x3FF71547, 0x60000000 =24b 1/ln2*/ -ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/ +C[] = { +0.0, +1.0, +2.0, +9007199254740992.0 , +1.0e300, +1.0e-300, +5.99999999999994648725e-01 , +4.28571428578550184252e-01 , +3.33333329818377432918e-01 , +2.72728123808534006489e-01 , +2.30660745775561754067e-01 , +2.06975017800338417784e-01 , +1.66666666666666019037e-01 , +-2.77777777770155933842e-03 , +6.61375632143793436117e-05 , +-1.65339022054652515390e-06 , +4.13813679705723846039e-08 , +6.93147180559945286227e-01 , +6.93147182464599609375e-01 , +-1.90465429995776804525e-09 , +8.0085662595372944372e-0017 , +9.61796693925975554329e-01 , +9.61796700954437255859e-01 , +-7.02846165095275826516e-09 , +1.44269504088896338700e+00 , +1.44269502162933349609e+00 , +1.92596299112661746887e-08 }; #ifdef __STDC__ double __ieee754_pow(double x, double y) @@ -107,7 +137,7 @@ ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/ #endif { double z,ax,z_h,z_l,p_h,p_l; - double y1,t1,t2,r,s,t,u,v,w; + double y1,t1,t2,r,s,t,u,v,w, t12,t14,r_1,r_2,r_3; int32_t i,j,k,yisint,n; int32_t hx,hy,ix,iy; u_int32_t lx,ly; @@ -117,7 +147,7 @@ ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/ ix = hx&0x7fffffff; iy = hy&0x7fffffff; /* y==zero: x**0 = 1 */ - if((iy|ly)==0) return one; + if((iy|ly)==0) return C[1]; /* +-NaN return x+y */ if(ix > 0x7ff00000 || ((ix==0x7ff00000)&&(lx!=0)) || @@ -150,12 +180,12 @@ ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/ if(((ix-0x3ff00000)|lx)==0) return y - y; /* inf**+-1 is NaN */ else if (ix >= 0x3ff00000)/* (|x|>1)**+-inf = inf,0 */ - return (hy>=0)? y: zero; + return (hy>=0)? y: C[0]; else /* (|x|<1)**-,+inf = inf,0 */ - return (hy<0)?-y: zero; + return (hy<0)?-y: C[0]; } if(iy==0x3ff00000) { /* y is +-1 */ - if(hy<0) return one/x; else return x; + if(hy<0) return C[1]/x; else return x; } if(hy==0x40000000) return x*x; /* y is 2 */ if(hy==0x3fe00000) { /* y is 0.5 */ @@ -169,7 +199,7 @@ ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/ if(lx==0) { if(ix==0x7ff00000||ix==0||ix==0x3ff00000){ z = ax; /*x is +-0,+-inf,+-1*/ - if(hy<0) z = one/z; /* z = (1/|x|) */ + if(hy<0) z = C[1]/z; /* z = (1/|x|) */ if(hx<0) { if(((ix-0x3ff00000)|yisint)==0) { z = (z-z)/(z-z); /* (-1)**non-int is NaN */ @@ -186,27 +216,27 @@ ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/ /* |y| is huge */ if(iy>0x41e00000) { /* if |y| > 2**31 */ if(iy>0x43f00000){ /* if |y| > 2**64, must o/uflow */ - if(ix<=0x3fefffff) return (hy<0)? huge*huge:tiny*tiny; - if(ix>=0x3ff00000) return (hy>0)? huge*huge:tiny*tiny; + if(ix<=0x3fefffff) return (hy<0)? C[4]*C[4]:C[5]*C[5]; + if(ix>=0x3ff00000) return (hy>0)? C[4]*C[4]:C[5]*C[5]; } /* over/underflow if x is not close to one */ - if(ix<0x3fefffff) return (hy<0)? huge*huge:tiny*tiny; - if(ix>0x3ff00000) return (hy>0)? huge*huge:tiny*tiny; + if(ix<0x3fefffff) return (hy<0)? C[4]*C[4]:C[5]*C[5]; + if(ix>0x3ff00000) return (hy>0)? C[4]*C[4]:C[5]*C[5]; /* now |1-x| is tiny <= 2**-20, suffice to compute log(x) by x-x^2/2+x^3/3-x^4/4 */ t = x-1; /* t has 20 trailing zeros */ w = (t*t)*(0.5-t*(0.3333333333333333333333-t*0.25)); - u = ivln2_h*t; /* ivln2_h has 21 sig. bits */ - v = t*ivln2_l-w*ivln2; + u = C[25]*t; /* ivln2_h has 21 sig. bits */ + v = t*C[26]-w*C[24]; t1 = u+v; SET_LOW_WORD(t1,0); t2 = v-(t1-u); } else { - double s2,s_h,s_l,t_h,t_l; + double s2,s_h,s_l,t_h,t_l,s22,s24,s26,r1,r2,r3; n = 0; /* take care subnormal number */ if(ix<0x00100000) - {ax *= two53; n -= 53; GET_HIGH_WORD(ix,ax); } + {ax *= C[3]; n -= 53; GET_HIGH_WORD(ix,ax); } n += ((ix)>>20)-0x3ff; j = ix&0x000fffff; /* determine interval */ @@ -218,18 +248,25 @@ ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/ /* compute s = s_h+s_l = (x-1)/(x+1) or (x-1.5)/(x+1.5) */ u = ax-bp[k]; /* bp[0]=1.0, bp[1]=1.5 */ - v = one/(ax+bp[k]); + v = C[1]/(ax+bp[k]); s = u*v; s_h = s; SET_LOW_WORD(s_h,0); /* t_h=ax+bp[k] High */ - t_h = zero; + t_h = C[0]; SET_HIGH_WORD(t_h,((ix>>1)|0x20000000)+0x00080000+(k<<18)); t_l = ax - (t_h-bp[k]); s_l = v*((u-s_h*t_h)-s_h*t_l); /* compute log(ax) */ s2 = s*s; +#ifdef DO_NOT_USE_THIS r = s2*s2*(L1+s2*(L2+s2*(L3+s2*(L4+s2*(L5+s2*L6))))); +#else + r1 = C[10]+s2*C[11]; s22=s2*s2; + r2 = C[8]+s2*C[9]; s24=s22*s22; + r3 = C[6]+s2*C[7]; s26=s24*s22; + r = r3*s22 + r2*s24 + r1*s26; +#endfi r += s_l*(s_h+s); s2 = s_h*s_h; t_h = 3.0+s2+r; @@ -242,8 +279,8 @@ ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/ p_h = u+v; SET_LOW_WORD(p_h,0); p_l = v-(p_h-u); - z_h = cp_h*p_h; /* cp_h+cp_l = 2/(3*log2) */ - z_l = cp_l*p_h+p_l*cp+dp_l[k]; + z_h = C[22]*p_h; /* cp_h+cp_l = 2/(3*log2) */ + z_l = C[23]*p_h+p_l*C[21]+dp_l[k]; /* log2(ax) = (s+..)*2/(3*log2) = n + dp_h + z_h + z_l */ t = (double)n; t1 = (((z_h+z_l)+dp_h[k])+t); @@ -251,9 +288,9 @@ ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/ t2 = z_l-(((t1-t)-dp_h[k])-z_h); } - s = one; /* s (sign of result -ve**odd) = -1 else = 1 */ + s = C[1]; /* s (sign of result -ve**odd) = -1 else = 1 */ if(((((u_int32_t)hx>>31)-1)|(yisint-1))==0) - s = -one;/* (-ve)**(odd int) */ + s = -C[1];/* (-ve)**(odd int) */ /* split up y into y1+y2 and compute (y1+y2)*(t1+t2) */ y1 = y; @@ -264,15 +301,15 @@ ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/ EXTRACT_WORDS(j,i,z); if (j>=0x40900000) { /* z >= 1024 */ if(((j-0x40900000)|i)!=0) /* if z > 1024 */ - return s*huge*huge; /* overflow */ + return s*C[4]*C[4]; /* overflow */ else { - if(p_l+ovt>z-p_h) return s*huge*huge; /* overflow */ + if(p_l+C[20]>z-p_h) return s*C[4]*C[4]; /* overflow */ } } else if((j&0x7fffffff)>=0x4090cc00 ) { /* z <= -1075 */ if(((j-0xc090cc00)|i)!=0) /* z < -1075 */ - return s*tiny*tiny; /* underflow */ + return s*C[5]*C[5]; /* underflow */ else { - if(p_l<=z-p_h) return s*tiny*tiny; /* underflow */ + if(p_l<=z-p_h) return s*C[5]*C[5]; /* underflow */ } } /* @@ -284,7 +321,7 @@ ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/ if(i>0x3fe00000) { /* if |z| > 0.5, set n = [z+0.5] */ n = j+(0x00100000>>(k+1)); k = ((n&0x7fffffff)>>20)-0x3ff; /* new k for n */ - t = zero; + t = C[0]; SET_HIGH_WORD(t,n&~(0x000fffff>>k)); n = ((n&0x000fffff)|0x00100000)>>(20-k); if(j<0) n = -n; @@ -292,14 +329,21 @@ ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/ } t = p_l+p_h; SET_LOW_WORD(t,0); - u = t*lg2_h; - v = (p_l-(t-p_h))*lg2+t*lg2_l; + u = t*C[18]; + v = (p_l-(t-p_h))*C[17]+t*C[19]; z = u+v; w = v-(z-u); t = z*z; - t1 = z - t*(P1+t*(P2+t*(P3+t*(P4+t*P5)))); - r = (z*t1)/(t1-two)-(w+z*w); - z = one-(r-z); +#ifdef DO_NOT_USE_THIS + t1 = z - t*(C[12]+t*(C[13]+t*(C[14]+t*(C[15]+t*C[16])))); +#else + r_1 = C[15]+t*C[16]; t12 = t*t; + r_2 = C[13]+t*C[14]; t14 = t12*t12; + r_3 = t*C[12]; + t1 = z - r_3 - t12*r_2 - t14*r_1; +#endif + r = (z*t1)/(t1-C[2])-(w+z*w); + z = C[1]-(r-z); GET_HIGH_WORD(j,z); j += (n<<20); if((j>>20)<=0) z = __scalbn(z,n); /* subnormal output */ |