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Diffstat (limited to 'pl/math/v_log2f_2u6.c')
| -rw-r--r-- | pl/math/v_log2f_2u6.c | 132 |
1 files changed, 0 insertions, 132 deletions
diff --git a/pl/math/v_log2f_2u6.c b/pl/math/v_log2f_2u6.c deleted file mode 100644 index aa011cd..0000000 --- a/pl/math/v_log2f_2u6.c +++ /dev/null @@ -1,132 +0,0 @@ -/* - * Single-precision vector log2 function. - * - * Copyright (c) 2022, Arm Limited. - * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception - */ - -#include "v_math.h" -#include "math_config.h" -#include "pl_sig.h" -#include "pl_test.h" - -#if V_SUPPORTED - -#define N (1 << V_LOG2F_TABLE_BITS) -#define T __v_log2f_data.tab -#define A __v_log2f_data.poly -#define OFF 0x3f330000 -#define SubnormLim 0x800000 -#define One v_u32 (0x3f800000) - -static float -handle_special (float x) -{ - if (x != x) - /* NaN - return NaN but do not trigger invalid. */ - return x; - if (x < 0) - /* log2f(-anything) = NaN. */ - return __math_invalidf (x); - if (x == 0) - /* log2f(0) = Inf. */ - return __math_divzerof (1); - /* log2f(Inf) = Inf. */ - return x; -} - -static float -normalise (float x) -{ - return asfloat (asuint (x * 0x1p23f) - (23 << 23)); -} - -#ifdef SCALAR - -#define DEFINE_LOOKUP_FUNC(p) \ - static inline float lookup_##p (uint32_t i) { return T[i].p; } - -#else - -#define DEFINE_LOOKUP_FUNC(p) \ - static inline v_f32_t lookup_##p (v_u32_t i) \ - { \ - return (v_f32_t){T[i[0]].p, T[i[1]].p, T[i[2]].p, T[i[3]].p}; \ - } - -#endif - -DEFINE_LOOKUP_FUNC (invc_lo) -DEFINE_LOOKUP_FUNC (invc_hi) -DEFINE_LOOKUP_FUNC (logc) - -/* Single-precision vector log2 routine. Implements the same algorithms as - scalar log2f, but using only single-precision arithmetic, with invc - represented as a two-limb float. Accurate to 2.6 ulp. The maximum error is - near sqrt(2): - __v_log2f(0x1.6a0484p+0) got 0x1.ffea02p-2 - want 0x1.ffea08p-2. */ -VPCS_ATTR v_f32_t V_NAME (log2f) (v_f32_t x) -{ - v_u32_t ix = v_as_u32_f32 (x); - - /* x is +-Inf, +-NaN, 0 or -ve. */ - v_u32_t special = v_cond_u32 (ix >= 0x7f800000) | v_cond_u32 (ix == 0); - /* |x| < 2^126 (i.e. x is subnormal). */ - v_u32_t subnorm = v_cond_u32 (ix < SubnormLim); - - /* Sidestep special lanes so they do not inadvertently trigger fenv - exceptions. They will be fixed up later. */ - if (unlikely (v_any_u32 (special))) - ix = v_sel_u32 (special, One, ix); - - if (unlikely (v_any_u32 (subnorm))) - { - /* Normalize any subnormals. */ - v_f32_t tmp_x = v_as_f32_u32 (ix); - ix = v_as_u32_f32 (v_call_f32 (normalise, tmp_x, tmp_x, subnorm)); - } - - /* x = 2^k z; where z is in range [OFF,2*OFF] and exact. - The range is split into N subintervals. - The ith subinterval contains z and c is near its center. */ - v_u32_t tmp = ix - OFF; - v_u32_t i = (tmp >> (23 - V_LOG2F_TABLE_BITS)) % N; - v_u32_t top = tmp & 0xff800000; - v_u32_t iz = ix - top; - v_f32_t k = v_to_f32_s32 (v_as_s32_u32 (tmp) >> 23); /* Arithmetic shift. */ - v_f32_t z = v_as_f32_u32 (iz); - - v_f32_t invc_lo = lookup_invc_lo (i); - v_f32_t invc_hi = lookup_invc_hi (i); - v_f32_t logc = lookup_logc (i); - - /* log2(x) = log1p(z/c-1)/ln2 + log2(c) + k. */ - v_f32_t r = v_fma_f32 (z, invc_hi, v_f32 (-1)); - r = v_fma_f32 (z, invc_lo, r); - v_f32_t y0 = logc + k; - - /* Pipelined polynomial evaluation to approximate log1p(r)/ln2. */ - v_f32_t r2 = r * r; - v_f32_t y = v_fma_f32 (v_f32 (A[1]), r, v_f32 (A[2])); - y = v_fma_f32 (v_f32 (A[0]), r2, y); - v_f32_t p = v_fma_f32 (v_f32 (A[3]), r, y0); - y = v_fma_f32 (y, r2, p); - - if (unlikely (v_any_u32 (special))) - return v_call_f32 (handle_special, x, y, special); - - return y; -} -VPCS_ALIAS - -PL_SIG (V, F, 1, log2, 0.01, 11.1) -PL_TEST_ULP (V_NAME (log2f), 2.10) -PL_TEST_EXPECT_FENV (V_NAME (log2f), WANT_ERRNO) -PL_TEST_INTERVAL (V_NAME (log2f), -0.0, -0x1p126, 100) -PL_TEST_INTERVAL (V_NAME (log2f), 0x1p-149, 0x1p-126, 4000) -PL_TEST_INTERVAL (V_NAME (log2f), 0x1p-126, 0x1p-23, 50000) -PL_TEST_INTERVAL (V_NAME (log2f), 0x1p-23, 1.0, 50000) -PL_TEST_INTERVAL (V_NAME (log2f), 1.0, 100, 50000) -PL_TEST_INTERVAL (V_NAME (log2f), 100, inf, 50000) -#endif |