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fb929067db
The new implementations are provided under !__OBSOLETE_MATH, they use ISO C99 code. There are several settings, with the default one the worst case error in nearest rounding mode is 0.509 ULP for exp and 0.507 ULP for exp2 when a multiply and add is contracted into an fma. They use a shared 2 KB lookup table, on aarch64 .text+.rodata size of libm.a is increased by 1868 bytes. The w_*.c wrappers are disabled for the new code as it takes care of error handling inline. The old exp2(x) code used to be just pow(2,x) so the speedup there is more significant. The file name has no special prefix to avoid any name collision with existing files. Improvements on Cortex-A72: exp latency: 3.2x exp thruput: 4.1x exp2 latency: 7.8x exp2 thruput: 18.8x
102 lines
2.9 KiB
C
102 lines
2.9 KiB
C
/* Double-precision math error handling.
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Copyright (c) 2018 ARM Ltd. All rights reserved.
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SPDX-License-Identifier: BSD-3-Clause
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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1. Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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3. The name of the company may not be used to endorse or promote
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products derived from this software without specific prior written
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permission.
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THIS SOFTWARE IS PROVIDED BY Arm LTD ``AS IS AND ANY EXPRESS OR IMPLIED
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WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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IN NO EVENT SHALL Arm LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
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#include "math_config.h"
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#if WANT_ERRNO
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#include <errno.h>
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/* NOINLINE reduces code size and avoids making math functions non-leaf
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when the error handling is inlined. */
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NOINLINE static double
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with_errno (double y, int e)
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{
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errno = e;
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return y;
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}
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#else
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#define with_errno(x, e) (x)
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#endif
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/* NOINLINE reduces code size. */
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NOINLINE static double
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xflow (uint32_t sign, double y)
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{
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y = opt_barrier_double (sign ? -y : y) * y;
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return with_errno (y, ERANGE);
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}
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HIDDEN double
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__math_uflow (uint32_t sign)
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{
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return xflow (sign, 0x1p-767);
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}
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#if WANT_ERRNO_UFLOW
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/* Underflows to zero in some non-nearest rounding mode, setting errno
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is valid even if the result is non-zero, but in the subnormal range. */
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HIDDEN double
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__math_may_uflow (uint32_t sign)
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{
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return xflow (sign, 0x1.8p-538);
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}
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#endif
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HIDDEN double
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__math_oflow (uint32_t sign)
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{
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return xflow (sign, 0x1p769);
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}
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HIDDEN double
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__math_divzero (uint32_t sign)
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{
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double y = opt_barrier_double (sign ? -1.0 : 1.0) / 0.0;
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return with_errno (y, ERANGE);
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}
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HIDDEN double
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__math_invalid (double x)
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{
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double y = (x - x) / (x - x);
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return isnan (x) ? y : with_errno (y, EDOM);
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}
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/* Check result and set errno if necessary. */
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HIDDEN double
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__math_check_uflow (double y)
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{
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return y == 0.0 ? with_errno (y, ERANGE) : y;
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}
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HIDDEN double
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__math_check_oflow (double y)
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{
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return isinf (y) ? with_errno (y, ERANGE) : y;
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}
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