From 08482af8d045312f51ce407adc689459fb45dbf2 Mon Sep 17 00:00:00 2001 From: Pierre Blanchard Date: Fri, 30 Dec 2022 11:57:50 +0000 Subject: pl/math: Add vector/SVE log2f New SVE routine is an SVE port of the Neon algorithm and is accurate to 2.48 ULPs. --- pl/math/include/mathlib.h | 2 ++ pl/math/sv_log2f_2u5.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 81 insertions(+) create mode 100644 pl/math/sv_log2f_2u5.c diff --git a/pl/math/include/mathlib.h b/pl/math/include/mathlib.h index 041b407..f05ad03 100644 --- a/pl/math/include/mathlib.h +++ b/pl/math/include/mathlib.h @@ -190,6 +190,7 @@ svfloat32_t __sv_logf_x (svfloat32_t, svbool_t); svfloat64_t __sv_log_x (svfloat64_t, svbool_t); svfloat32_t __sv_log10f_x (svfloat32_t, svbool_t); svfloat64_t __sv_log10_x (svfloat64_t, svbool_t); +svfloat32_t __sv_log2f_x (svfloat32_t, svbool_t); svfloat32_t __sv_powif_x (svfloat32_t, svint32_t, svbool_t); svfloat64_t __sv_powi_x (svfloat64_t, svint64_t, svbool_t); svfloat32_t __sv_sinf_x (svfloat32_t, svbool_t); @@ -210,6 +211,7 @@ svfloat32_t _ZGVsMxv_logf (svfloat32_t, svbool_t); svfloat64_t _ZGVsMxv_log (svfloat64_t, svbool_t); svfloat32_t _ZGVsMxv_log10f (svfloat32_t, svbool_t); svfloat64_t _ZGVsMxv_log10 (svfloat64_t, svbool_t); +svfloat32_t _ZGVsMxv_log2f (svfloat32_t, svbool_t); svfloat32_t _ZGVsMxvv_powi(svfloat32_t, svint32_t, svbool_t); svfloat64_t _ZGVsMxvv_powk(svfloat64_t, svint64_t, svbool_t); svfloat32_t _ZGVsMxv_sinf (svfloat32_t, svbool_t); diff --git a/pl/math/sv_log2f_2u5.c b/pl/math/sv_log2f_2u5.c new file mode 100644 index 0000000..6488658 --- /dev/null +++ b/pl/math/sv_log2f_2u5.c @@ -0,0 +1,79 @@ +/* + * Single-precision vector/SVE log2 function. + * + * Copyright (c) 2022, Arm Limited. + * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception + */ + +#include "sv_math.h" +#include "pl_sig.h" +#include "pl_test.h" + +#if SV_SUPPORTED + +#define P(i) __v_log2f_data.poly[i] + +#define Ln2 (0x1.62e43p-1f) /* 0x3f317218. */ +#define Min (0x00800000) +#define Max (0x7f800000) +#define Mask (0x007fffff) +#define Off (0x3f2aaaab) /* 0.666667. */ + +static NOINLINE sv_f32_t +specialcase (sv_f32_t x, sv_f32_t y, svbool_t cmp) +{ + return sv_call_f32 (log2f, x, y, cmp); +} + +/* Optimised implementation of SVE log2f, using the same algorithm + and polynomial as Neon log2f. Maximum error is 2.48 ULPs: + __sv_log2f(0x1.558174p+0) got 0x1.a9be84p-2 + want 0x1.a9be8p-2. */ +sv_f32_t +__sv_log2f_x (sv_f32_t x, const svbool_t pg) +{ + sv_u32_t u = sv_as_u32_f32 (x); + svbool_t special + = svcmpge_u32 (pg, svsub_n_u32_x (pg, u, Min), sv_u32 (Max - Min)); + + /* x = 2^n * (1+r), where 2/3 < 1+r < 4/3. */ + u = svsub_n_u32_x (pg, u, Off); + sv_f32_t n = sv_to_f32_s32_x (pg, svasr_n_s32_x (pg, sv_as_s32_u32 (u), + 23)); /* Sign-extend. */ + u = svand_n_u32_x (pg, u, Mask); + u = svadd_n_u32_x (pg, u, Off); + sv_f32_t r = svsub_n_f32_x (pg, sv_as_f32_u32 (u), 1.0f); + + /* y = log2(1+r) + n. */ + sv_f32_t r2 = svmul_f32_x (pg, r, r); + + /* Evaluate polynomial using pairwise Horner scheme. */ + sv_f32_t p67 = sv_fma_n_f32_x (pg, P (7), r, sv_f32 (P (6))); + sv_f32_t p45 = sv_fma_n_f32_x (pg, P (5), r, sv_f32 (P (4))); + sv_f32_t p23 = sv_fma_n_f32_x (pg, P (3), r, sv_f32 (P (2))); + sv_f32_t p01 = sv_fma_n_f32_x (pg, P (1), r, sv_f32 (P (0))); + sv_f32_t y; + y = sv_fma_n_f32_x (pg, P (8), r2, p67); + y = sv_fma_f32_x (pg, y, r2, p45); + y = sv_fma_f32_x (pg, y, r2, p23); + y = sv_fma_f32_x (pg, y, r2, p01); + y = sv_fma_f32_x (pg, y, r, n); + + if (unlikely (svptest_any (pg, special))) + return specialcase (x, y, special); + return y; +} + +PL_ALIAS (__sv_log2f_x, _ZGVsMxv_log2f) + +PL_SIG (SV, F, 1, log2, 0.01, 11.1) +PL_TEST_ULP (__sv_log2f, 1.99) +PL_TEST_EXPECT_FENV_ALWAYS (__sv_log2f) +PL_TEST_INTERVAL (__sv_log2f, -0.0, -0x1p126, 4000) +PL_TEST_INTERVAL (__sv_log2f, 0.0, 0x1p-126, 4000) +PL_TEST_INTERVAL (__sv_log2f, 0x1p-126, 0x1p-23, 50000) +PL_TEST_INTERVAL (__sv_log2f, 0x1p-23, 1.0, 50000) +PL_TEST_INTERVAL (__sv_log2f, 1.0, 100, 50000) +PL_TEST_INTERVAL (__sv_log2f, 100, inf, 50000) + +#endif // SV_SUPPORTED -- cgit v1.2.3