You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
74 lines
1.7 KiB
74 lines
1.7 KiB
4 months ago
|
/*
|
||
|
|
* Single-precision vector log function.
|
||
|
|
*
|
||
|
|
* Copyright (c) 2019, Arm Limited.
|
||
|
|
* SPDX-License-Identifier: MIT
|
||
|
|
*/
|
||
|
|
|
||
|
|
#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
|