1*f3087befSAndrew Turner /*
2*f3087befSAndrew Turner * Double-precision SVE cospi(x) function.
3*f3087befSAndrew Turner *
4*f3087befSAndrew Turner * Copyright (c) 2023-2024, Arm Limited.
5*f3087befSAndrew Turner * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
6*f3087befSAndrew Turner */
7*f3087befSAndrew Turner
8*f3087befSAndrew Turner #include "sv_math.h"
9*f3087befSAndrew Turner #include "mathlib.h"
10*f3087befSAndrew Turner #include "test_sig.h"
11*f3087befSAndrew Turner #include "test_defs.h"
12*f3087befSAndrew Turner #include "sv_poly_f64.h"
13*f3087befSAndrew Turner
14*f3087befSAndrew Turner static const struct data
15*f3087befSAndrew Turner {
16*f3087befSAndrew Turner double poly[10];
17*f3087befSAndrew Turner double range_val;
18*f3087befSAndrew Turner } data = {
19*f3087befSAndrew Turner /* Polynomial coefficients generated using Remez algorithm,
20*f3087befSAndrew Turner see sinpi.sollya for details. */
21*f3087befSAndrew Turner .poly = { 0x1.921fb54442d184p1, -0x1.4abbce625be53p2, 0x1.466bc6775ab16p1,
22*f3087befSAndrew Turner -0x1.32d2cce62dc33p-1, 0x1.507834891188ep-4, -0x1.e30750a28c88ep-8,
23*f3087befSAndrew Turner 0x1.e8f48308acda4p-12, -0x1.6fc0032b3c29fp-16,
24*f3087befSAndrew Turner 0x1.af86ae521260bp-21, -0x1.012a9870eeb7dp-25 },
25*f3087befSAndrew Turner .range_val = 0x1p53,
26*f3087befSAndrew Turner };
27*f3087befSAndrew Turner
28*f3087befSAndrew Turner /* A fast SVE implementation of cospi.
29*f3087befSAndrew Turner Maximum error 3.20 ULP:
30*f3087befSAndrew Turner _ZGVsMxv_cospi(0x1.f18ba32c63159p-6) got 0x1.fdabf595f9763p-1
31*f3087befSAndrew Turner want 0x1.fdabf595f9766p-1. */
SV_NAME_D1(cospi)32*f3087befSAndrew Turner svfloat64_t SV_NAME_D1 (cospi) (svfloat64_t x, const svbool_t pg)
33*f3087befSAndrew Turner {
34*f3087befSAndrew Turner const struct data *d = ptr_barrier (&data);
35*f3087befSAndrew Turner
36*f3087befSAndrew Turner /* Using cospi(x) = sinpi(0.5 - x)
37*f3087befSAndrew Turner range reduction and offset into sinpi range -1/2 .. 1/2
38*f3087befSAndrew Turner r = 0.5 - |x - rint(x)|. */
39*f3087befSAndrew Turner svfloat64_t n = svrinta_x (pg, x);
40*f3087befSAndrew Turner svfloat64_t r = svsub_x (pg, x, n);
41*f3087befSAndrew Turner r = svsub_x (pg, sv_f64 (0.5), svabs_x (pg, r));
42*f3087befSAndrew Turner
43*f3087befSAndrew Turner /* Result should be negated based on if n is odd or not.
44*f3087befSAndrew Turner If ax >= 2^53, the result will always be positive. */
45*f3087befSAndrew Turner svbool_t cmp = svaclt (pg, x, d->range_val);
46*f3087befSAndrew Turner svuint64_t intn = svreinterpret_u64 (svcvt_s64_z (pg, n));
47*f3087befSAndrew Turner svuint64_t sign = svlsl_z (cmp, intn, 63);
48*f3087befSAndrew Turner
49*f3087befSAndrew Turner /* y = sin(r). */
50*f3087befSAndrew Turner svfloat64_t r2 = svmul_x (pg, r, r);
51*f3087befSAndrew Turner svfloat64_t r4 = svmul_x (pg, r2, r2);
52*f3087befSAndrew Turner svfloat64_t y = sv_pw_horner_9_f64_x (pg, r2, r4, d->poly);
53*f3087befSAndrew Turner y = svmul_x (pg, y, r);
54*f3087befSAndrew Turner
55*f3087befSAndrew Turner return svreinterpret_f64 (sveor_x (pg, svreinterpret_u64 (y), sign));
56*f3087befSAndrew Turner }
57*f3087befSAndrew Turner
58*f3087befSAndrew Turner #if WANT_TRIGPI_TESTS
59*f3087befSAndrew Turner TEST_ULP (SV_NAME_D1 (cospi), 2.71)
60*f3087befSAndrew Turner TEST_DISABLE_FENV (SV_NAME_D1 (cospi))
61*f3087befSAndrew Turner TEST_SYM_INTERVAL (SV_NAME_D1 (cospi), 0, 0x1p-63, 5000)
62*f3087befSAndrew Turner TEST_SYM_INTERVAL (SV_NAME_D1 (cospi), 0x1p-63, 0.5, 10000)
63*f3087befSAndrew Turner TEST_SYM_INTERVAL (SV_NAME_D1 (cospi), 0.5, 0x1p51, 10000)
64*f3087befSAndrew Turner TEST_SYM_INTERVAL (SV_NAME_D1 (cospi), 0x1p51, inf, 100000)
65*f3087befSAndrew Turner #endif
66*f3087befSAndrew Turner CLOSE_SVE_ATTR
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