1 /*
2 * Single-precision SVE cospi(x) function.
3 *
4 * Copyright (c) 2023-2024, Arm Limited.
5 * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
6 */
7
8 #include "sv_math.h"
9 #include "mathlib.h"
10 #include "test_sig.h"
11 #include "test_defs.h"
12 #include "sv_poly_f32.h"
13
14 static const struct data
15 {
16 float poly[6];
17 float range_val;
18 } data = {
19 /* Taylor series coefficents for sin(pi * x). */
20 .poly = { 0x1.921fb6p1f, -0x1.4abbcep2f, 0x1.466bc6p1f, -0x1.32d2ccp-1f,
21 0x1.50783p-4f, -0x1.e30750p-8f },
22 .range_val = 0x1p31f,
23 };
24
25 /* A fast SVE implementation of cospif.
26 Maximum error: 2.60 ULP:
27 _ZGVsMxv_cospif(+/-0x1.cae664p-4) got 0x1.e09c9ep-1
28 want 0x1.e09c98p-1. */
SV_NAME_F1(cospi)29 svfloat32_t SV_NAME_F1 (cospi) (svfloat32_t x, const svbool_t pg)
30 {
31 const struct data *d = ptr_barrier (&data);
32
33 /* Using cospi(x) = sinpi(0.5 - x)
34 range reduction and offset into sinpi range -1/2 .. 1/2
35 r = 0.5 - |x - rint(x)|. */
36 svfloat32_t n = svrinta_x (pg, x);
37 svfloat32_t r = svsub_x (pg, x, n);
38 r = svsub_x (pg, sv_f32 (0.5f), svabs_x (pg, r));
39
40 /* Result should be negated based on if n is odd or not.
41 If ax >= 2^31, the result will always be positive. */
42 svbool_t cmp = svaclt (pg, x, d->range_val);
43 svuint32_t intn = svreinterpret_u32 (svcvt_s32_x (pg, n));
44 svuint32_t sign = svlsl_z (cmp, intn, 31);
45
46 /* y = sin(r). */
47 svfloat32_t r2 = svmul_x (pg, r, r);
48 svfloat32_t y = sv_horner_5_f32_x (pg, r2, d->poly);
49 y = svmul_x (pg, y, r);
50
51 return svreinterpret_f32 (sveor_x (pg, svreinterpret_u32 (y), sign));
52 }
53
54 #if WANT_TRIGPI_TESTS
55 TEST_ULP (SV_NAME_F1 (cospi), 2.08)
56 TEST_DISABLE_FENV (SV_NAME_F1 (cospi))
57 TEST_SYM_INTERVAL (SV_NAME_F1 (cospi), 0, 0x1p-31, 5000)
58 TEST_SYM_INTERVAL (SV_NAME_F1 (cospi), 0x1p-31, 0.5, 10000)
59 TEST_SYM_INTERVAL (SV_NAME_F1 (cospi), 0.5, 0x1p31f, 10000)
60 TEST_SYM_INTERVAL (SV_NAME_F1 (cospi), 0x1p31f, inf, 10000)
61 #endif
62 CLOSE_SVE_ATTR
63