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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 2 | pj | 1 | /* e_sqrtf.c -- float version of e_sqrt.c. |
| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
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| 3 | */ |
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| 4 | |||
| 5 | /* |
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| 6 | * ==================================================== |
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| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 8 | * |
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| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 10 | * Permission to use, copy, modify, and distribute this |
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| 11 | * software is freely granted, provided that this notice |
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| 12 | * is preserved. |
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| 13 | * ==================================================== |
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| 14 | */ |
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| 15 | |||
| 16 | #ifndef lint |
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| 17 | static char rcsid[] = "$\Id: e_sqrtf.c,v 1.2 1995/05/30 05:48:52 rgrimes Exp $"; |
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| 18 | #endif |
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| 19 | |||
| 20 | #include "math.h" |
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| 21 | #include "math_private.h" |
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| 22 | |||
| 23 | #ifdef __STDC__ |
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| 24 | static const float one = 1.0, tiny=1.0e-30; |
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| 25 | #else |
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| 26 | static float one = 1.0, tiny=1.0e-30; |
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| 27 | #endif |
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| 28 | |||
| 29 | #ifdef __STDC__ |
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| 30 | float __ieee754_sqrtf(float x) |
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| 31 | #else |
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| 32 | float __ieee754_sqrtf(x) |
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| 33 | float x; |
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| 34 | #endif |
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| 35 | { |
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| 36 | float z; |
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| 37 | int32_t sign = (int)0x80000000; |
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| 38 | int32_t ix,s,q,m,t,i; |
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| 39 | u_int32_t r; |
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| 40 | |||
| 41 | GET_FLOAT_WORD(ix,x); |
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| 42 | |||
| 43 | /* take care of Inf and NaN */ |
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| 44 | if((ix&0x7f800000)==0x7f800000) { |
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| 45 | return x*x+x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf |
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| 46 | sqrt(-inf)=sNaN */ |
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| 47 | } |
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| 48 | /* take care of zero */ |
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| 49 | if(ix<=0) { |
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| 50 | if((ix&(~sign))==0) return x;/* sqrt(+-0) = +-0 */ |
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| 51 | else if(ix<0) |
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| 52 | return (x-x)/(x-x); /* sqrt(-ve) = sNaN */ |
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| 53 | } |
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| 54 | /* normalize x */ |
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| 55 | m = (ix>>23); |
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| 56 | if(m==0) { /* subnormal x */ |
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| 57 | for(i=0;(ix&0x00800000)==0;i++) ix<<=1; |
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| 58 | m -= i-1; |
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| 59 | } |
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| 60 | m -= 127; /* unbias exponent */ |
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| 61 | ix = (ix&0x007fffff)|0x00800000; |
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| 62 | if(m&1) /* odd m, double x to make it even */ |
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| 63 | ix += ix; |
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| 64 | m >>= 1; /* m = [m/2] */ |
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| 65 | |||
| 66 | /* generate sqrt(x) bit by bit */ |
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| 67 | ix += ix; |
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| 68 | q = s = 0; /* q = sqrt(x) */ |
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| 69 | r = 0x01000000; /* r = moving bit from right to left */ |
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| 70 | |||
| 71 | while(r!=0) { |
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| 72 | t = s+r; |
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| 73 | if(t<=ix) { |
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| 74 | s = t+r; |
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| 75 | ix -= t; |
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| 76 | q += r; |
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| 77 | } |
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| 78 | ix += ix; |
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| 79 | r>>=1; |
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| 80 | } |
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| 81 | |||
| 82 | /* use floating add to find out rounding direction */ |
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| 83 | if(ix!=0) { |
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| 84 | z = one-tiny; /* trigger inexact flag */ |
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| 85 | if (z>=one) { |
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| 86 | z = one+tiny; |
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| 87 | if (z>one) |
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| 88 | q += 2; |
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| 89 | else |
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| 90 | q += (q&1); |
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| 91 | } |
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| 92 | } |
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| 93 | ix = (q>>1)+0x3f000000; |
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| 94 | ix += (m <<23); |
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| 95 | SET_FLOAT_WORD(z,ix); |
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| 96 | return z; |
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| 97 | } |