| /* |
| * Double-precision SVE e^(x+tail) function. |
| * |
| * Copyright (c) 2021-2023, Arm Limited. |
| * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception |
| */ |
| |
| #ifndef SV_EXP_TAIL_H |
| #define SV_EXP_TAIL_H |
| |
| #include "sv_math.h" |
| #if SV_SUPPORTED |
| |
| #include "v_exp_tail.h" |
| |
| #define C1 sv_f64 (C1_scal) |
| #define C2 sv_f64 (C2_scal) |
| #define C3 sv_f64 (C3_scal) |
| #define MinusLn2hi (-Ln2hi_scal) |
| #define MinusLn2lo (-Ln2lo_scal) |
| |
| #define N (1 << V_EXP_TAIL_TABLE_BITS) |
| #define Tab __v_exp_tail_data |
| #define IndexMask (N - 1) |
| #define Shift sv_f64 (0x1.8p+52) |
| #define Thres 704.0 |
| |
| static inline sv_f64_t |
| sv_exp_tail_special_case (svbool_t pg, sv_f64_t s, sv_f64_t y, sv_f64_t n) |
| { |
| sv_f64_t absn = svabs_f64_x (pg, n); |
| |
| /* 2^(n/N) may overflow, break it up into s1*s2. */ |
| sv_u64_t b = svsel_u64 (svcmple_n_f64 (pg, n, 0), sv_u64 (0x6000000000000000), |
| sv_u64 (0)); |
| sv_f64_t s1 = sv_as_f64_u64 (svsubr_n_u64_x (pg, b, 0x7000000000000000)); |
| sv_f64_t s2 = sv_as_f64_u64 ( |
| svadd_u64_x (pg, svsub_n_u64_x (pg, sv_as_u64_f64 (s), 0x3010000000000000), |
| b)); |
| |
| svbool_t cmp = svcmpgt_n_f64 (pg, absn, 1280.0 * N); |
| sv_f64_t r1 = svmul_f64_x (pg, s1, s1); |
| sv_f64_t r0 = svmul_f64_x (pg, sv_fma_f64_x (pg, y, s2, s2), s1); |
| return svsel_f64 (cmp, r1, r0); |
| } |
| |
| static inline sv_f64_t |
| sv_exp_tail (const svbool_t pg, sv_f64_t x, sv_f64_t xtail) |
| { |
| /* Calculate exp(x + xtail). */ |
| sv_f64_t z = sv_fma_n_f64_x (pg, InvLn2_scal, x, Shift); |
| sv_f64_t n = svsub_f64_x (pg, z, Shift); |
| |
| sv_f64_t r = sv_fma_n_f64_x (pg, MinusLn2hi, n, x); |
| r = sv_fma_n_f64_x (pg, MinusLn2lo, n, r); |
| |
| sv_u64_t u = sv_as_u64_f64 (z); |
| sv_u64_t e = svlsl_n_u64_x (pg, u, 52 - V_EXP_TAIL_TABLE_BITS); |
| sv_u64_t i = svand_n_u64_x (pg, u, IndexMask); |
| |
| sv_f64_t y = sv_fma_f64_x (pg, C3, r, C2); |
| y = sv_fma_f64_x (pg, y, r, C1); |
| y = sv_fma_f64_x (pg, y, r, sv_f64 (1.0)); |
| y = sv_fma_f64_x (pg, y, r, xtail); |
| |
| /* s = 2^(n/N). */ |
| u = sv_lookup_u64_x (pg, Tab, i); |
| sv_f64_t s = sv_as_f64_u64 (svadd_u64_x (pg, u, e)); |
| |
| svbool_t cmp = svcmpgt_n_f64 (pg, svabs_f64_x (pg, x), Thres); |
| if (unlikely (svptest_any (pg, cmp))) |
| { |
| return sv_exp_tail_special_case (pg, s, y, n); |
| } |
| return sv_fma_f64_x (pg, y, s, s); |
| } |
| |
| #endif |
| #endif |