diff options
Diffstat (limited to 'pl/math/v_log1pf_inline.h')
| -rw-r--r-- | pl/math/v_log1pf_inline.h | 74 |
1 files changed, 43 insertions, 31 deletions
diff --git a/pl/math/v_log1pf_inline.h b/pl/math/v_log1pf_inline.h index e3048e667c26..c654c6bad08f 100644 --- a/pl/math/v_log1pf_inline.h +++ b/pl/math/v_log1pf_inline.h @@ -10,46 +10,58 @@ #define PL_MATH_V_LOG1PF_INLINE_H #include "v_math.h" -#include "math_config.h" +#include "poly_advsimd_f32.h" -#define Four 0x40800000 -#define Ln2 v_f32 (0x1.62e43p-1f) - -#define C(i) v_f32 (__log1pf_data.coeffs[i]) - -static inline v_f32_t -eval_poly (v_f32_t m) +struct v_log1pf_data { - /* Approximate log(1+m) on [-0.25, 0.5] using Estrin scheme. */ - v_f32_t p_12 = v_fma_f32 (m, C (1), C (0)); - v_f32_t p_34 = v_fma_f32 (m, C (3), C (2)); - v_f32_t p_56 = v_fma_f32 (m, C (5), C (4)); - v_f32_t p_78 = v_fma_f32 (m, C (7), C (6)); + float32x4_t poly[8], ln2; + uint32x4_t four; + int32x4_t three_quarters; +}; - v_f32_t m2 = m * m; - v_f32_t p_02 = v_fma_f32 (m2, p_12, m); - v_f32_t p_36 = v_fma_f32 (m2, p_56, p_34); - v_f32_t p_79 = v_fma_f32 (m2, C (8), p_78); +/* Polynomial generated using FPMinimax in [-0.25, 0.5]. First two coefficients + (1, -0.5) are not stored as they can be generated more efficiently. */ +#define V_LOG1PF_CONSTANTS_TABLE \ + { \ + .poly \ + = { V4 (0x1.5555aap-2f), V4 (-0x1.000038p-2f), V4 (0x1.99675cp-3f), \ + V4 (-0x1.54ef78p-3f), V4 (0x1.28a1f4p-3f), V4 (-0x1.0da91p-3f), \ + V4 (0x1.abcb6p-4f), V4 (-0x1.6f0d5ep-5f) }, \ + .ln2 = V4 (0x1.62e43p-1f), .four = V4 (0x40800000), \ + .three_quarters = V4 (0x3f400000) \ + } - v_f32_t m4 = m2 * m2; - v_f32_t p_06 = v_fma_f32 (m4, p_36, p_02); - - return v_fma_f32 (m4, m4 * p_79, p_06); +static inline float32x4_t +eval_poly (float32x4_t m, const float32x4_t *c) +{ + /* Approximate log(1+m) on [-0.25, 0.5] using pairwise Horner (main routine + uses split Estrin, but this way reduces register pressure in the calling + routine). */ + float32x4_t q = vfmaq_f32 (v_f32 (-0.5), m, c[0]); + float32x4_t m2 = vmulq_f32 (m, m); + q = vfmaq_f32 (m, m2, q); + float32x4_t p = v_pw_horner_6_f32 (m, m2, c + 1); + p = vmulq_f32 (m2, p); + return vfmaq_f32 (q, m2, p); } -static inline v_f32_t -log1pf_inline (v_f32_t x) +static inline float32x4_t +log1pf_inline (float32x4_t x, const struct v_log1pf_data d) { /* Helper for calculating log(x + 1). Copied from log1pf_2u1.c, with no special-case handling. See that file for details of the algorithm. */ - v_f32_t m = x + 1.0f; - v_u32_t k = (v_as_u32_f32 (m) - 0x3f400000) & 0xff800000; - v_f32_t s = v_as_f32_u32 (v_u32 (Four) - k); - v_f32_t m_scale = v_as_f32_u32 (v_as_u32_f32 (x) - k) - + v_fma_f32 (v_f32 (0.25f), s, v_f32 (-1.0f)); - v_f32_t p = eval_poly (m_scale); - v_f32_t scale_back = v_to_f32_u32 (k) * 0x1.0p-23f; - return v_fma_f32 (scale_back, Ln2, p); + float32x4_t m = vaddq_f32 (x, v_f32 (1.0f)); + int32x4_t k + = vandq_s32 (vsubq_s32 (vreinterpretq_s32_f32 (m), d.three_quarters), + v_s32 (0xff800000)); + uint32x4_t ku = vreinterpretq_u32_s32 (k); + float32x4_t s = vreinterpretq_f32_u32 (vsubq_u32 (d.four, ku)); + float32x4_t m_scale + = vreinterpretq_f32_u32 (vsubq_u32 (vreinterpretq_u32_f32 (x), ku)); + m_scale = vaddq_f32 (m_scale, vfmaq_f32 (v_f32 (-1.0f), v_f32 (0.25f), s)); + float32x4_t p = eval_poly (m_scale, d.poly); + float32x4_t scale_back = vmulq_f32 (vcvtq_f32_s32 (k), v_f32 (0x1.0p-23f)); + return vfmaq_f32 (p, scale_back, d.ln2); } #endif // PL_MATH_V_LOG1PF_INLINE_H |