| /* |
| * Single-precision vector log function. |
| * |
| * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| * See https://llvm.org/LICENSE.txt for license information. |
| * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| */ |
| |
| #include "mathlib.h" |
| #include "v_math.h" |
| #if V_SUPPORTED |
| |
| static const float Poly[] = { |
| /* 3.34 ulp error */ |
| -0x1.3e737cp-3f, 0x1.5a9aa2p-3f, -0x1.4f9934p-3f, 0x1.961348p-3f, |
| -0x1.00187cp-2f, 0x1.555d7cp-2f, -0x1.ffffc8p-2f, |
| }; |
| #define P7 v_f32 (Poly[0]) |
| #define P6 v_f32 (Poly[1]) |
| #define P5 v_f32 (Poly[2]) |
| #define P4 v_f32 (Poly[3]) |
| #define P3 v_f32 (Poly[4]) |
| #define P2 v_f32 (Poly[5]) |
| #define P1 v_f32 (Poly[6]) |
| |
| #define Ln2 v_f32 (0x1.62e43p-1f) /* 0x3f317218 */ |
| #define Min v_u32 (0x00800000) |
| #define Max v_u32 (0x7f800000) |
| #define Mask v_u32 (0x007fffff) |
| #define Off v_u32 (0x3f2aaaab) /* 0.666667 */ |
| |
| VPCS_ATTR |
| __attribute__ ((noinline)) static v_f32_t |
| specialcase (v_f32_t x, v_f32_t y, v_u32_t cmp) |
| { |
| /* Fall back to scalar code. */ |
| return v_call_f32 (logf, x, y, cmp); |
| } |
| |
| VPCS_ATTR |
| v_f32_t |
| V_NAME(logf) (v_f32_t x) |
| { |
| v_f32_t n, p, q, r, r2, y; |
| v_u32_t u, cmp; |
| |
| u = v_as_u32_f32 (x); |
| cmp = v_cond_u32 (u - Min >= Max - Min); |
| |
| /* x = 2^n * (1+r), where 2/3 < 1+r < 4/3 */ |
| u -= Off; |
| n = v_to_f32_s32 (v_as_s32_u32 (u) >> 23); /* signextend */ |
| u &= Mask; |
| u += Off; |
| r = v_as_f32_u32 (u) - v_f32 (1.0f); |
| |
| /* y = log(1+r) + n*ln2. */ |
| r2 = r * r; |
| /* n*ln2 + r + r2*(P1 + r*P2 + r2*(P3 + r*P4 + r2*(P5 + r*P6 + r2*P7))). */ |
| p = v_fma_f32 (P6, r, P5); |
| q = v_fma_f32 (P4, r, P3); |
| y = v_fma_f32 (P2, r, P1); |
| p = v_fma_f32 (P7, r2, p); |
| q = v_fma_f32 (p, r2, q); |
| y = v_fma_f32 (q, r2, y); |
| p = v_fma_f32 (Ln2, n, r); |
| y = v_fma_f32 (y, r2, p); |
| |
| if (unlikely (v_any_u32 (cmp))) |
| return specialcase (x, y, cmp); |
| return y; |
| } |
| VPCS_ALIAS |
| #endif |