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
16 // Evaluate polynomial using Horner's Scheme:
17 // With polyeval(x, a_0, a_1, ..., a_n) = a_n * x^n + ... + a_1 * x + a_0, we
18 // evaluated it as: a_0 + x * (a_1 + x * ( ... (a_(n-1) + x * a_n) ... ) ) ).
19 // We will use FMA instructions if available.
20 // Example: to evaluate x^3 + 2*x^2 + 3*x + 4, call
21 // polyeval( x, 4.0, 3.0, 2.0, 1.0 )
22
23 namespace LIBC_NAMESPACE {
24 namespace fputil {
25
26 template <typename T>
27 LIBC_INLINE cpp::enable_if_t<(sizeof(T) > sizeof(void *)), T>
polyeval(const T &,const T & a0)28 polyeval(const T &, const T &a0) {
29 return a0;
30 }
31
32 template <typename T>
polyeval(T,T a0)33 LIBC_INLINE cpp::enable_if_t<(sizeof(T) <= sizeof(void *)), T> polyeval(T,
34 T a0) {
35 return a0;
36 }
37
38 template <typename T, typename... Ts>
39 LIBC_INLINE cpp::enable_if_t<(sizeof(T) > sizeof(void *)), T>
polyeval(const T & x,const T & a0,const Ts &...a)40 polyeval(const T &x, const T &a0, const Ts &...a) {
41 return multiply_add(x, polyeval(x, a...), a0);
42 }
43
44 template <typename T, typename... Ts>
45 LIBC_INLINE cpp::enable_if_t<(sizeof(T) <= sizeof(void *)), T>
polyeval(T x,T a0,Ts...a)46 polyeval(T x, T a0, Ts... a) {
47 return multiply_add(x, polyeval(x, a...), a0);
48 }
49
50 } // namespace fputil
51 } // namespace LIBC_NAMESPACE
52
53 #endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_POLYEVAL_H
54