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| 1 | //===-- Common header for PolyEval implementations --------------*- C++ -*-===// |
|---|---|
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #ifndef LLVM_LIBC_SRC___SUPPORT_FPUTIL_POLYEVAL_H |
| 10 | #define LLVM_LIBC_SRC___SUPPORT_FPUTIL_POLYEVAL_H |
| 11 | |
| 12 | #include "multiply_add.h" |
| 13 | #include "src/__support/CPP/type_traits.h" |
| 14 | #include "src/__support/common.h" |
| 15 | #include "src/__support/macros/config.h" |
| 16 | |
| 17 | // Evaluate polynomial using Horner's Scheme: |
| 18 | // With polyeval(x, a_0, a_1, ..., a_n) = a_n * x^n + ... + a_1 * x + a_0, we |
| 19 | // evaluated it as: a_0 + x * (a_1 + x * ( ... (a_(n-1) + x * a_n) ... ) ) ). |
| 20 | // We will use FMA instructions if available. |
| 21 | // Example: to evaluate x^3 + 2*x^2 + 3*x + 4, call |
| 22 | // polyeval( x, 4.0, 3.0, 2.0, 1.0 ) |
| 23 | |
| 24 | namespace LIBC_NAMESPACE_DECL { |
| 25 | namespace fputil { |
| 26 | |
| 27 | template <typename T> |
| 28 | LIBC_INLINE cpp::enable_if_t<(sizeof(T) > sizeof(void *)), T> |
| 29 | polyeval(const T &, const T &a0) { |
| 30 | return a0; |
| 31 | } |
| 32 | |
| 33 | template <typename T> |
| 34 | LIBC_INLINE cpp::enable_if_t<(sizeof(T) <= sizeof(void *)), T> polyeval(T, |
| 35 | T a0) { |
| 36 | return a0; |
| 37 | } |
| 38 | |
| 39 | template <typename T, typename... Ts> |
| 40 | LIBC_INLINE cpp::enable_if_t<(sizeof(T) > sizeof(void *)), T> |
| 41 | polyeval(const T &x, const T &a0, const Ts &...a) { |
| 42 | return multiply_add(x, polyeval(x, a...), a0); |
| 43 | } |
| 44 | |
| 45 | template <typename T, typename... Ts> |
| 46 | LIBC_INLINE cpp::enable_if_t<(sizeof(T) <= sizeof(void *)), T> |
| 47 | polyeval(T x, T a0, Ts... a) { |
| 48 | return multiply_add(x, polyeval(x, a...), a0); |
| 49 | } |
| 50 | |
| 51 | } // namespace fputil |
| 52 | } // namespace LIBC_NAMESPACE_DECL |
| 53 | |
| 54 | #endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_POLYEVAL_H |
| 55 |
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