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64 lines
2.1 KiB
C
64 lines
2.1 KiB
C
/* Math functions for i387.
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Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by John C. Bowman <bowman@ipp-garching.mpg.de>, 1995.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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Boston, MA 02110-1301, USA.
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*/
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#include <math.h>
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double exp (double __x);
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double exp (double __x)
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{
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#ifdef __GNUC__
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register double __value, __exponent;
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__asm __volatile__
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("fldl2e # e^x = 2^(x * log2(e))\n\t"
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"fmul %%st(1) # x * log2(e)\n\t"
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"fst %%st(1)\n\t"
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"frndint # int(x * log2(e))\n\t"
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"fxch\n\t"
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"fsub %%st(1) # fract(x * log2(e))\n\t"
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"f2xm1 # 2^(fract(x * log2(e))) - 1\n\t"
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: "=t" (__value), "=u" (__exponent) : "0" (__x));
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__value += 1.0;
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__asm __volatile__
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("fscale"
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: "=t" (__value) : "0" (__value), "u" (__exponent));
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return __value;
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#else
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register double __val;
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__asm
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{
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fld1 // store 1.0 for later use
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fld __x
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fldl2e // e^x = 2^(x * log2(e))
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fmul st,st(1) // x * log2(e)
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fld st(0)
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frndint // int(x * log2(e))
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fsub st,st(1) // fract(x * log2(e))
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fxch
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f2xm1 // 2^(fract(x * log2(e))) - 1
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fadd st,st(3) // + 1.0
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fscale
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fstp __val
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}
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return __val;
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#endif /*__GNUC__*/
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}
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