diff options
Diffstat (limited to 'pl/math/v_log1pf_2u1.c')
| -rw-r--r-- | pl/math/v_log1pf_2u1.c | 126 |
1 files changed, 0 insertions, 126 deletions
diff --git a/pl/math/v_log1pf_2u1.c b/pl/math/v_log1pf_2u1.c deleted file mode 100644 index 153c88da9c88..000000000000 --- a/pl/math/v_log1pf_2u1.c +++ /dev/null @@ -1,126 +0,0 @@ -/* - * Single-precision vector log(1+x) function. - * - * Copyright (c) 2022-2023, Arm Limited. - * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception - */ - -#include "v_math.h" -#include "pl_sig.h" -#include "pl_test.h" -#include "poly_advsimd_f32.h" - -const static struct data -{ - float32x4_t poly[8], ln2; - uint32x4_t tiny_bound, minus_one, four, thresh; - int32x4_t three_quarters; -} data = { - .poly = { /* Generated using FPMinimax in [-0.25, 0.5]. First two coefficients - (1, -0.5) are not stored as they can be generated more - efficiently. */ - 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), - .tiny_bound = V4 (0x34000000), /* asuint32(0x1p-23). ulp=0.5 at 0x1p-23. */ - .thresh = V4 (0x4b800000), /* asuint32(INFINITY) - tiny_bound. */ - .minus_one = V4 (0xbf800000), - .four = V4 (0x40800000), - .three_quarters = V4 (0x3f400000) -}; - -static inline float32x4_t -eval_poly (float32x4_t m, const float32x4_t *p) -{ - /* Approximate log(1+m) on [-0.25, 0.5] using split Estrin scheme. */ - float32x4_t p_12 = vfmaq_f32 (v_f32 (-0.5), m, p[0]); - float32x4_t p_34 = vfmaq_f32 (p[1], m, p[2]); - float32x4_t p_56 = vfmaq_f32 (p[3], m, p[4]); - float32x4_t p_78 = vfmaq_f32 (p[5], m, p[6]); - - float32x4_t m2 = vmulq_f32 (m, m); - float32x4_t p_02 = vfmaq_f32 (m, m2, p_12); - float32x4_t p_36 = vfmaq_f32 (p_34, m2, p_56); - float32x4_t p_79 = vfmaq_f32 (p_78, m2, p[7]); - - float32x4_t m4 = vmulq_f32 (m2, m2); - float32x4_t p_06 = vfmaq_f32 (p_02, m4, p_36); - return vfmaq_f32 (p_06, m4, vmulq_f32 (m4, p_79)); -} - -static float32x4_t NOINLINE VPCS_ATTR -special_case (float32x4_t x, float32x4_t y, uint32x4_t special) -{ - return v_call_f32 (log1pf, x, y, special); -} - -/* Vector log1pf approximation using polynomial on reduced interval. Accuracy - is roughly 2.02 ULP: - log1pf(0x1.21e13ap-2) got 0x1.fe8028p-3 want 0x1.fe802cp-3. */ -VPCS_ATTR float32x4_t V_NAME_F1 (log1p) (float32x4_t x) -{ - const struct data *d = ptr_barrier (&data); - - uint32x4_t ix = vreinterpretq_u32_f32 (x); - uint32x4_t ia = vreinterpretq_u32_f32 (vabsq_f32 (x)); - uint32x4_t special_cases - = vorrq_u32 (vcgeq_u32 (vsubq_u32 (ia, d->tiny_bound), d->thresh), - vcgeq_u32 (ix, d->minus_one)); - float32x4_t special_arg = x; - -#if WANT_SIMD_EXCEPT - if (unlikely (v_any_u32 (special_cases))) - /* Side-step special lanes so fenv exceptions are not triggered - inadvertently. */ - x = v_zerofy_f32 (x, special_cases); -#endif - - /* With x + 1 = t * 2^k (where t = m + 1 and k is chosen such that m - is in [-0.25, 0.5]): - log1p(x) = log(t) + log(2^k) = log1p(m) + k*log(2). - - We approximate log1p(m) with a polynomial, then scale by - k*log(2). Instead of doing this directly, we use an intermediate - scale factor s = 4*k*log(2) to ensure the scale is representable - as a normalised fp32 number. */ - - float32x4_t m = vaddq_f32 (x, v_f32 (1.0f)); - - /* Choose k to scale x to the range [-1/4, 1/2]. */ - int32x4_t k - = vandq_s32 (vsubq_s32 (vreinterpretq_s32_f32 (m), d->three_quarters), - v_s32 (0xff800000)); - uint32x4_t ku = vreinterpretq_u32_s32 (k); - - /* Scale x by exponent manipulation. */ - float32x4_t m_scale - = vreinterpretq_f32_u32 (vsubq_u32 (vreinterpretq_u32_f32 (x), ku)); - - /* Scale up to ensure that the scale factor is representable as normalised - fp32 number, and scale m down accordingly. */ - float32x4_t s = vreinterpretq_f32_u32 (vsubq_u32 (d->four, ku)); - m_scale = vaddq_f32 (m_scale, vfmaq_f32 (v_f32 (-1.0f), v_f32 (0.25f), s)); - - /* Evaluate polynomial on the reduced interval. */ - float32x4_t p = eval_poly (m_scale, d->poly); - - /* The scale factor to be applied back at the end - by multiplying float(k) - by 2^-23 we get the unbiased exponent of k. */ - float32x4_t scale_back = vcvtq_f32_s32 (vshrq_n_s32 (k, 23)); - - /* Apply the scaling back. */ - float32x4_t y = vfmaq_f32 (p, scale_back, d->ln2); - - if (unlikely (v_any_u32 (special_cases))) - return special_case (special_arg, y, special_cases); - return y; -} - -PL_SIG (V, F, 1, log1p, -0.9, 10.0) -PL_TEST_ULP (V_NAME_F1 (log1p), 1.53) -PL_TEST_EXPECT_FENV (V_NAME_F1 (log1p), WANT_SIMD_EXCEPT) -PL_TEST_SYM_INTERVAL (V_NAME_F1 (log1p), 0.0, 0x1p-23, 30000) -PL_TEST_SYM_INTERVAL (V_NAME_F1 (log1p), 0x1p-23, 1, 50000) -PL_TEST_INTERVAL (V_NAME_F1 (log1p), 1, inf, 50000) -PL_TEST_INTERVAL (V_NAME_F1 (log1p), -1.0, -inf, 1000) |