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Merged from double precision case (e_pow.c 1.10: sign fixes).

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This commit is contained in:
Bruce Evans 2004-06-01 19:33:30 +00:00
parent 302b450136
commit f88a48cc43
1 changed files with 14 additions and 13 deletions
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27
lib/msun/src/e_powf.c
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@ -57,7 +57,7 @@ float
__ieee754_powf(float x, float y)
{
float z,ax,z_h,z_l,p_h,p_l;
float y1,t1,t2,r,s,t,u,v,w;
float y1,t1,t2,r,s,sn,t,u,v,w;
int32_t i,j,k,yisint,n;
int32_t hx,hy,ix,iy,is;
@ -120,14 +120,19 @@ __ieee754_powf(float x, float y)
return z;
}
n = ((u_int32_t)hx>>31)-1;
/* (x<0)**(non-int) is NaN */
if(((((u_int32_t)hx>>31)-1)|yisint)==0) return (x-x)/(x-x);
if((n|yisint)==0) return (x-x)/(x-x);
sn = one; /* s (sign of result -ve**odd) = -1 else = 1 */
if((n|(yisint-1))==0) sn = -one;/* (-ve)**(odd int) */
/* |y| is huge */
if(iy>0x4d000000) { /* if |y| > 2**27 */
/* over/underflow if x is not close to one */
if(ix<0x3f7ffff8) return (hy<0)? huge*huge:tiny*tiny;
if(ix>0x3f800007) return (hy>0)? huge*huge:tiny*tiny;
if(ix<0x3f7ffff8) return (hy<0)? sn*huge*huge:sn*tiny*tiny;
if(ix>0x3f800007) return (hy>0)? sn*huge*huge:sn*tiny*tiny;
/* now |1-x| is tiny <= 2**-20, suffice to compute
log(x) by x-x^2/2+x^3/3-x^4/4 */
t = ax-1; /* t has 20 trailing zeros */
@ -192,10 +197,6 @@ __ieee754_powf(float x, float y)
t2 = z_l-(((t1-t)-dp_h[k])-z_h);
}
s = one; /* s (sign of result -ve**odd) = -1 else = 1 */
if(((((u_int32_t)hx>>31)-1)|(yisint-1))==0)
s = -one; /* (-ve)**(odd int) */
/* split up y into y1+y2 and compute (y1+y2)*(t1+t2) */
GET_FLOAT_WORD(is,y);
SET_FLOAT_WORD(y1,is&0xfffff000);
@ -204,14 +205,14 @@ __ieee754_powf(float x, float y)
z = p_l+p_h;
GET_FLOAT_WORD(j,z);
if (j>0x43000000) /* if z > 128 */
return s*huge*huge; /* overflow */
return sn*huge*huge; /* overflow */
else if (j==0x43000000) { /* if z == 128 */
if(p_l+ovt>z-p_h) return s*huge*huge; /* overflow */
if(p_l+ovt>z-p_h) return sn*huge*huge; /* overflow */
}
else if ((j&0x7fffffff)>0x43160000) /* z <= -150 */
return s*tiny*tiny; /* underflow */
return sn*tiny*tiny; /* underflow */
else if (j==0xc3160000){ /* z == -150 */
if(p_l<=z-p_h) return s*tiny*tiny; /* underflow */
if(p_l<=z-p_h) return sn*tiny*tiny; /* underflow */
}
/*
* compute 2**(p_h+p_l)
@ -242,5 +243,5 @@ __ieee754_powf(float x, float y)
j += (n<<23);
if((j>>23)<=0) z = scalbnf(z,n); /* subnormal output */
else SET_FLOAT_WORD(z,j);
return s*z;
return sn*z;
}