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220622dde5
This patch adds a new macro, libm_alias_finite, to define all _finite symbol. It sets all _finite symbol as compat symbol based on its first version (obtained from the definition at built generated first-versions.h). The <fn>f128_finite symbols were introduced in GLIBC 2.26 and so need special treatment in code that is shared between long double and float128. It is done by adding a list, similar to internal symbol redifinition, on sysdeps/ieee754/float128/float128_private.h. Alpha also needs some tricky changes to ensure we still emit 2 compat symbols for sqrt(f). Passes buildmanyglibc. Co-authored-by: Adhemerval Zanella <adhemerval.zanella@linaro.org> Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
115 lines
3.2 KiB
C
115 lines
3.2 KiB
C
/* Single-precision e^x function.
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Copyright (C) 2017-2020 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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#ifdef __expf
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# undef libm_hidden_proto
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# define libm_hidden_proto(ignored)
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#endif
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#include <math.h>
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#include <math-narrow-eval.h>
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#include <stdint.h>
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#include <libm-alias-finite.h>
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#include <libm-alias-float.h>
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#include "math_config.h"
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/*
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EXP2F_TABLE_BITS = 5
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EXP2F_POLY_ORDER = 3
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ULP error: 0.502 (nearest rounding.)
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Relative error: 1.69 * 2^-34 in [-ln2/64, ln2/64] (before rounding.)
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Wrong count: 170635 (all nearest rounding wrong results with fma.)
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Non-nearest ULP error: 1 (rounded ULP error)
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*/
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#define N (1 << EXP2F_TABLE_BITS)
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#define InvLn2N __exp2f_data.invln2_scaled
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#define T __exp2f_data.tab
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#define C __exp2f_data.poly_scaled
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static inline uint32_t
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top12 (float x)
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{
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return asuint (x) >> 20;
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}
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float
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__expf (float x)
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{
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uint32_t abstop;
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uint64_t ki, t;
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/* double_t for better performance on targets with FLT_EVAL_METHOD==2. */
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double_t kd, xd, z, r, r2, y, s;
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xd = (double_t) x;
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abstop = top12 (x) & 0x7ff;
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if (__glibc_unlikely (abstop >= top12 (88.0f)))
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{
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/* |x| >= 88 or x is nan. */
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if (asuint (x) == asuint (-INFINITY))
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return 0.0f;
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if (abstop >= top12 (INFINITY))
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return x + x;
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if (x > 0x1.62e42ep6f) /* x > log(0x1p128) ~= 88.72 */
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return __math_oflowf (0);
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if (x < -0x1.9fe368p6f) /* x < log(0x1p-150) ~= -103.97 */
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return __math_uflowf (0);
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#if WANT_ERRNO_UFLOW
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if (x < -0x1.9d1d9ep6f) /* x < log(0x1p-149) ~= -103.28 */
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return __math_may_uflowf (0);
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#endif
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}
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/* x*N/Ln2 = k + r with r in [-1/2, 1/2] and int k. */
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z = InvLn2N * xd;
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/* Round and convert z to int, the result is in [-150*N, 128*N] and
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ideally ties-to-even rule is used, otherwise the magnitude of r
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can be bigger which gives larger approximation error. */
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#if TOINT_INTRINSICS
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kd = roundtoint (z);
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ki = converttoint (z);
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#else
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# define SHIFT __exp2f_data.shift
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kd = math_narrow_eval ((double) (z + SHIFT)); /* Needs to be double. */
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ki = asuint64 (kd);
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kd -= SHIFT;
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#endif
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r = z - kd;
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/* exp(x) = 2^(k/N) * 2^(r/N) ~= s * (C0*r^3 + C1*r^2 + C2*r + 1) */
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t = T[ki % N];
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t += ki << (52 - EXP2F_TABLE_BITS);
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s = asdouble (t);
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z = C[0] * r + C[1];
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r2 = r * r;
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y = C[2] * r + 1;
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y = z * r2 + y;
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y = y * s;
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return (float) y;
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}
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#ifndef __expf
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hidden_def (__expf)
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strong_alias (__expf, __ieee754_expf)
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libm_alias_finite (__ieee754_expf, __expf)
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versioned_symbol (libm, __expf, expf, GLIBC_2_27);
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libm_alias_float_other (__exp, exp)
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#endif
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