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85 lines
2.7 KiB
C
85 lines
2.7 KiB
C
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/*******************************************************************************
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MIT License
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-----------
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Copyright (c) 2002-2019 Advanced Micro Devices, Inc.
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this Software and associated documentaon files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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*******************************************************************************/
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#include "libm.h"
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#include "libm_util.h"
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#define USE_INFINITY_WITH_FLAGS
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#define USE_HANDLE_ERROR
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#include "libm_inlines.h"
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#undef USE_INFINITY_WITH_FLAGS
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#undef USE_HANDLE_ERROR
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#include "libm_errno.h"
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double _logb(double x)
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{
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unsigned long long ux;
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long long u;
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GET_BITS_DP64(x, ux);
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u = ((ux & EXPBITS_DP64) >> EXPSHIFTBITS_DP64) - EXPBIAS_DP64;
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if ((ux & ~SIGNBIT_DP64) == 0)
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/* x is +/-zero. Return -infinity with div-by-zero flag. */
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return _handle_error("_logb", OP_LOGB, NINFBITPATT_DP64, _SING,
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AMD_F_DIVBYZERO, ERANGE, x, 0.0, 1);
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else if (EMIN_DP64 <= u && u <= EMAX_DP64)
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/* x is a normal number */
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return (double)u;
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else if (u > EMAX_DP64)
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{
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/* x is infinity or NaN */
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if ((ux & MANTBITS_DP64) == 0)
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/* x is +/-infinity. For VC++, return infinity of same sign. */
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return x;
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else
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/* x is NaN, result is NaN */
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return _handle_error("_logb", OP_LOGB, ux|0x0008000000000000, _DOMAIN,
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0, EDOM, x, 0.0, 1);
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}
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else
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{
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/* x is denormalized. */
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#ifdef FOLLOW_IEEE754_LOGB
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/* Return the value of the minimum exponent to ensure that
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the relationship between logb and scalb, defined in
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IEEE 754, holds. */
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return EMIN_DP64;
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#else
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/* Follow the rule set by IEEE 854 for logb */
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ux &= MANTBITS_DP64;
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u = EMIN_DP64;
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while (ux < IMPBIT_DP64)
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{
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ux <<= 1;
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u--;
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}
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return (double)u;
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#endif
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}
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}
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