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f165e244e4
Refactor the generic implementation to use math_config.h definitions, and add an alternative one if the ABI supports truncf instructions (gated through math-use-builtins-trunc.h). The generic implementation generates similar code on x86_64, while the optimization one for aarch64 (where truncf is supported as a builtin by through frintz), the improvements are: reciprocal-throughput master patch difference workload-0_1 3.0595 3.0698 -0.34% workload-1_maxint 5.1747 3.0542 40.98% workload-maxint_maxfloat 3.4391 3.0349 11.75% workload-integral 3.2732 3.0293 7.45% latency master patch difference workload-0_1 3.5267 4.7107 -33.57% workload-1_maxint 6.9074 4.7282 31.55% workload-maxint_maxfloat 3.7210 4.7506 -27.67% workload-integral 3.8634 4.8137 -24.60% Checked on aarch64-linux-gnu and x86_64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
70 lines
1.8 KiB
C
70 lines
1.8 KiB
C
/* Extract signed integral and fractional values.
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Copyright (C) 1993-2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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, see
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<https://www.gnu.org/licenses/>. */
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#include <math.h>
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#include <libm-alias-double.h>
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#include "math_config.h"
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#include <math-use-builtins-trunc.h>
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double
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__modf (double x, double *iptr)
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{
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uint64_t t = asuint64 (x);
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#if USE_TRUNC_BUILTIN
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if (is_inf (t))
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{
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*iptr = x;
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return copysign (0.0, x);
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}
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*iptr = trunc (x);
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return copysign (x - *iptr, x);
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#else
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int e = get_exponent (t);
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/* No fraction part. */
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if (e < MANTISSA_WIDTH)
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{
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if (e < 0)
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{
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/* |x|<1 -> *iptr = +-0 */
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*iptr = asdouble (t & SIGN_MASK);
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return x;
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}
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uint64_t i = MANTISSA_MASK >> e;
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if ((t & i) == 0)
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{
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/* x in integral, return +-0 */
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*iptr = x;
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return asdouble (t & SIGN_MASK);
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}
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*iptr = asdouble (t & ~i);
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return x - *iptr;
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}
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/* Set invalid operation for sNaN. */
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*iptr = x * 1.0;
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if ((e == 0x400) && (t & MANTISSA_MASK))
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return *iptr;
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return asdouble (t & SIGN_MASK);
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#endif
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}
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#ifndef __modf
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libm_alias_double (__modf, modf)
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#endif
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