1 /* 2 * Single-precision SVE tanh(x) function. 3 * 4 * Copyright (c) 2023, Arm Limited. 5 * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception 6 */ 7 8 #include "sv_math.h" 9 #include "pl_sig.h" 10 #include "pl_test.h" 11 12 #include "sv_expm1f_inline.h" 13 14 static const struct data 15 { 16 struct sv_expm1f_data expm1f_consts; 17 uint32_t boring_bound, onef; 18 } data = { 19 .expm1f_consts = SV_EXPM1F_DATA, 20 /* 0x1.205966p+3, above which tanhf rounds to 1 (or -1 for negative). */ 21 .boring_bound = 0x41102cb3, 22 .onef = 0x3f800000, 23 }; 24 25 static svfloat32_t NOINLINE 26 special_case (svfloat32_t x, svfloat32_t y, svbool_t special) 27 { 28 return sv_call_f32 (tanhf, x, y, special); 29 } 30 31 /* Approximation for single-precision SVE tanh(x), using a simplified 32 version of expm1f. The maximum error is 2.57 ULP: 33 _ZGVsMxv_tanhf (0x1.fc1832p-5) got 0x1.fb71a4p-5 34 want 0x1.fb71aap-5. */ 35 svfloat32_t SV_NAME_F1 (tanh) (svfloat32_t x, const svbool_t pg) 36 { 37 const struct data *d = ptr_barrier (&data); 38 39 svfloat32_t ax = svabs_x (pg, x); 40 svuint32_t iax = svreinterpret_u32 (ax); 41 svuint32_t sign = sveor_x (pg, svreinterpret_u32 (x), iax); 42 svbool_t is_boring = svcmpgt (pg, iax, d->boring_bound); 43 svfloat32_t boring = svreinterpret_f32 (svorr_x (pg, sign, d->onef)); 44 45 svbool_t special = svcmpgt (pg, iax, 0x7f800000); 46 47 /* tanh(x) = (e^2x - 1) / (e^2x + 1). */ 48 svfloat32_t q = expm1f_inline (svmul_x (pg, x, 2.0), pg, &d->expm1f_consts); 49 svfloat32_t y = svdiv_x (pg, q, svadd_x (pg, q, 2.0)); 50 if (unlikely (svptest_any (pg, special))) 51 return special_case (x, svsel_f32 (is_boring, boring, y), special); 52 return svsel_f32 (is_boring, boring, y); 53 } 54 55 PL_SIG (SV, F, 1, tanh, -10.0, 10.0) 56 PL_TEST_ULP (SV_NAME_F1 (tanh), 2.07) 57 PL_TEST_SYM_INTERVAL (SV_NAME_F1 (tanh), 0, 0x1p-23, 1000) 58 PL_TEST_SYM_INTERVAL (SV_NAME_F1 (tanh), 0x1p-23, 0x1.205966p+3, 100000) 59 PL_TEST_SYM_INTERVAL (SV_NAME_F1 (tanh), 0x1.205966p+3, inf, 100) 60