52 lines
1.5 KiB
C
52 lines
1.5 KiB
C
/* s_scalbnf.c -- float version of s_scalbn.c.
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*/
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#include <math.h>
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#include <math_private.h>
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static const float
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two25 = 3.355443200e+07, /* 0x4c000000 */
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twom25 = 2.9802322388e-08, /* 0x33000000 */
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huge = 1.0e+30,
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tiny = 1.0e-30;
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float
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__scalbnf (float x, int n)
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{
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int32_t k,ix;
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GET_FLOAT_WORD(ix,x);
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k = (ix&0x7f800000)>>23; /* extract exponent */
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if (__builtin_expect(k==0, 0)) { /* 0 or subnormal x */
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if ((ix&0x7fffffff)==0) return x; /* +-0 */
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x *= two25;
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GET_FLOAT_WORD(ix,x);
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k = ((ix&0x7f800000)>>23) - 25;
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}
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if (__builtin_expect(k==0xff, 0)) return x+x; /* NaN or Inf */
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if (__builtin_expect(n< -50000, 0))
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return tiny*copysignf(tiny,x); /*underflow*/
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if (__builtin_expect(n> 50000 || k+n > 0xfe, 0))
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return huge*copysignf(huge,x); /* overflow */
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/* Now k and n are bounded we know that k = k+n does not
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overflow. */
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k = k+n;
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if (__builtin_expect(k > 0, 1)) /* normal result */
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{SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
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if (k <= -25)
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return tiny*copysignf(tiny,x); /*underflow*/
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k += 25; /* subnormal result */
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SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
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return x*twom25;
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}
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