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1/*2 * Single-precision vector log function.3 *4 * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.5 * See https://llvm.org/LICENSE.txt for license information.6 * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception7 */8 9#include "mathlib.h"10#include "v_math.h"11#if V_SUPPORTED12 13static const float Poly[] = {14 /* 3.34 ulp error */15 -0x1.3e737cp-3f, 0x1.5a9aa2p-3f, -0x1.4f9934p-3f, 0x1.961348p-3f,16 -0x1.00187cp-2f, 0x1.555d7cp-2f, -0x1.ffffc8p-2f,17};18#define P7 v_f32 (Poly[0])19#define P6 v_f32 (Poly[1])20#define P5 v_f32 (Poly[2])21#define P4 v_f32 (Poly[3])22#define P3 v_f32 (Poly[4])23#define P2 v_f32 (Poly[5])24#define P1 v_f32 (Poly[6])25 26#define Ln2 v_f32 (0x1.62e43p-1f) /* 0x3f317218 */27#define Min v_u32 (0x00800000)28#define Max v_u32 (0x7f800000)29#define Mask v_u32 (0x007fffff)30#define Off v_u32 (0x3f2aaaab) /* 0.666667 */31 32VPCS_ATTR33__attribute__ ((noinline)) static v_f32_t34specialcase (v_f32_t x, v_f32_t y, v_u32_t cmp)35{36 /* Fall back to scalar code. */37 return v_call_f32 (logf, x, y, cmp);38}39 40VPCS_ATTR41v_f32_t42V_NAME(logf) (v_f32_t x)43{44 v_f32_t n, p, q, r, r2, y;45 v_u32_t u, cmp;46 47 u = v_as_u32_f32 (x);48 cmp = v_cond_u32 (u - Min >= Max - Min);49 50 /* x = 2^n * (1+r), where 2/3 < 1+r < 4/3 */51 u -= Off;52 n = v_to_f32_s32 (v_as_s32_u32 (u) >> 23); /* signextend */53 u &= Mask;54 u += Off;55 r = v_as_f32_u32 (u) - v_f32 (1.0f);56 57 /* y = log(1+r) + n*ln2. */58 r2 = r * r;59 /* n*ln2 + r + r2*(P1 + r*P2 + r2*(P3 + r*P4 + r2*(P5 + r*P6 + r2*P7))). */60 p = v_fma_f32 (P6, r, P5);61 q = v_fma_f32 (P4, r, P3);62 y = v_fma_f32 (P2, r, P1);63 p = v_fma_f32 (P7, r2, p);64 q = v_fma_f32 (p, r2, q);65 y = v_fma_f32 (q, r2, y);66 p = v_fma_f32 (Ln2, n, r);67 y = v_fma_f32 (y, r2, p);68 69 if (unlikely (v_any_u32 (cmp)))70 return specialcase (x, y, cmp);71 return y;72}73VPCS_ALIAS74#endif75