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e302e10213
This includes a fix for big-endian in AdvSIMD log, some cosmetic changes, and numerous small optimisations mainly around inlining and using indexed variants of MLA intrinsics. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
113 lines
3.8 KiB
C
113 lines
3.8 KiB
C
/* Single-precision SVE atan2
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Copyright (C) 2023-2024 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 "sv_math.h"
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#include "poly_sve_f32.h"
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static const struct data
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{
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float32_t poly[8];
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float32_t pi_over_2;
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} data = {
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/* Coefficients of polynomial P such that atan(x)~x+x*P(x^2) on
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[2**-128, 1.0]. */
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.poly = { -0x1.55555p-2f, 0x1.99935ep-3f, -0x1.24051ep-3f, 0x1.bd7368p-4f,
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-0x1.491f0ep-4f, 0x1.93a2c0p-5f, -0x1.4c3c60p-6f, 0x1.01fd88p-8f },
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.pi_over_2 = 0x1.921fb6p+0f,
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};
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/* Special cases i.e. 0, infinity, nan (fall back to scalar calls). */
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static svfloat32_t NOINLINE
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special_case (svfloat32_t y, svfloat32_t x, svfloat32_t ret,
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const svbool_t cmp)
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{
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return sv_call2_f32 (atan2f, y, x, ret, cmp);
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}
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/* Returns a predicate indicating true if the input is the bit representation
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of 0, infinity or nan. */
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static inline svbool_t
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zeroinfnan (svuint32_t i, const svbool_t pg)
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{
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return svcmpge (pg, svsub_x (pg, svlsl_x (pg, i, 1), 1),
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sv_u32 (2 * 0x7f800000lu - 1));
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}
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/* Fast implementation of SVE atan2f based on atan(x) ~ shift + z + z^3 *
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P(z^2) with reduction to [0,1] using z=1/x and shift = pi/2. Maximum
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observed error is 2.95 ULP:
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_ZGVsMxvv_atan2f (0x1.93836cp+6, 0x1.8cae1p+6) got 0x1.967f06p-1
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want 0x1.967f00p-1. */
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svfloat32_t SV_NAME_F2 (atan2) (svfloat32_t y, svfloat32_t x, const svbool_t pg)
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{
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const struct data *data_ptr = ptr_barrier (&data);
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svuint32_t ix = svreinterpret_u32 (x);
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svuint32_t iy = svreinterpret_u32 (y);
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svbool_t cmp_x = zeroinfnan (ix, pg);
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svbool_t cmp_y = zeroinfnan (iy, pg);
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svbool_t cmp_xy = svorr_z (pg, cmp_x, cmp_y);
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svfloat32_t ax = svabs_x (pg, x);
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svfloat32_t ay = svabs_x (pg, y);
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svuint32_t iax = svreinterpret_u32 (ax);
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svuint32_t iay = svreinterpret_u32 (ay);
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svuint32_t sign_x = sveor_x (pg, ix, iax);
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svuint32_t sign_y = sveor_x (pg, iy, iay);
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svuint32_t sign_xy = sveor_x (pg, sign_x, sign_y);
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svbool_t pred_aygtax = svcmpgt (pg, ay, ax);
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/* Set up z for call to atan. */
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svfloat32_t n = svsel (pred_aygtax, svneg_x (pg, ax), ay);
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svfloat32_t d = svsel (pred_aygtax, ay, ax);
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svfloat32_t z = svdiv_x (pg, n, d);
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/* Work out the correct shift. */
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svfloat32_t shift = svreinterpret_f32 (svlsr_x (pg, sign_x, 1));
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shift = svsel (pred_aygtax, sv_f32 (1.0), shift);
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shift = svreinterpret_f32 (svorr_x (pg, sign_x, svreinterpret_u32 (shift)));
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shift = svmul_x (pg, shift, sv_f32 (data_ptr->pi_over_2));
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/* Use pure Estrin scheme for P(z^2) with deg(P)=7. */
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svfloat32_t z2 = svmul_x (pg, z, z);
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svfloat32_t z4 = svmul_x (pg, z2, z2);
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svfloat32_t z8 = svmul_x (pg, z4, z4);
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svfloat32_t ret = sv_estrin_7_f32_x (pg, z2, z4, z8, data_ptr->poly);
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/* ret = shift + z + z^3 * P(z^2). */
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svfloat32_t z3 = svmul_x (pg, z2, z);
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ret = svmla_x (pg, z, z3, ret);
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ret = svadd_m (pg, ret, shift);
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/* Account for the sign of x and y. */
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if (__glibc_unlikely (svptest_any (pg, cmp_xy)))
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return special_case (
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y, x,
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svreinterpret_f32 (sveor_x (pg, svreinterpret_u32 (ret), sign_xy)),
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cmp_xy);
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return svreinterpret_f32 (sveor_x (pg, svreinterpret_u32 (ret), sign_xy));
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}
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