59 lines
1.9 KiB
C
59 lines
1.9 KiB
C
/* Copyright (C) 2007, 2009 Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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#define BID_128RES
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#include "bid_internal.h"
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BID128_FUNCTION_ARG1_NORND_CUSTOMRESTYPE(int, bid128_logb, x)
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UINT128 CX;
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UINT64 sign_x;
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SINT64 D;
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int_float f64, fx;
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int exponent_x, bin_expon_cx, digits;
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if (!unpack_BID128_value (&sign_x, &exponent_x, &CX, x)) {
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#ifdef SET_STATUS_FLAGS
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__set_status_flags (pfpsf, INVALID_EXCEPTION);
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#endif
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BID_RETURN_VAL (0x80000000);
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}
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// find number of digits in coefficient
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// 2^64
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f64.i = 0x5f800000;
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// fx ~ CX
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fx.d = (float) CX.w[1] * f64.d + (float) CX.w[0];
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bin_expon_cx = ((fx.i >> 23) & 0xff) - 0x7f;
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digits = estimate_decimal_digits[bin_expon_cx];
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// scale = 38-estimate_decimal_digits[bin_expon_cx];
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D = CX.w[1] - power10_index_binexp_128[bin_expon_cx].w[1];
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if (D > 0 || (!D && CX.w[0] >= power10_index_binexp_128[bin_expon_cx].w[0])) {
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digits++;
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}
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exponent_x = exponent_x - DECIMAL_EXPONENT_BIAS_128 - 1 + digits;
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BID_RETURN_VAL (exponent_x);
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}
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