1*bb722a7dSDimitry Andric //===-- Common header for PolyEval implementations --------------*- C++ -*-===//
2*bb722a7dSDimitry Andric //
3*bb722a7dSDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4*bb722a7dSDimitry Andric // See https://llvm.org/LICENSE.txt for license information.
5*bb722a7dSDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6*bb722a7dSDimitry Andric //
7*bb722a7dSDimitry Andric //===----------------------------------------------------------------------===//
8*bb722a7dSDimitry Andric
9*bb722a7dSDimitry Andric #ifndef LLVM_LIBC_SRC___SUPPORT_FPUTIL_POLYEVAL_H
10*bb722a7dSDimitry Andric #define LLVM_LIBC_SRC___SUPPORT_FPUTIL_POLYEVAL_H
11*bb722a7dSDimitry Andric
12*bb722a7dSDimitry Andric #include "multiply_add.h"
13*bb722a7dSDimitry Andric #include "src/__support/CPP/type_traits.h"
14*bb722a7dSDimitry Andric #include "src/__support/common.h"
15*bb722a7dSDimitry Andric #include "src/__support/macros/config.h"
16*bb722a7dSDimitry Andric
17*bb722a7dSDimitry Andric // Evaluate polynomial using Horner's Scheme:
18*bb722a7dSDimitry Andric // With polyeval(x, a_0, a_1, ..., a_n) = a_n * x^n + ... + a_1 * x + a_0, we
19*bb722a7dSDimitry Andric // evaluated it as: a_0 + x * (a_1 + x * ( ... (a_(n-1) + x * a_n) ... ) ) ).
20*bb722a7dSDimitry Andric // We will use FMA instructions if available.
21*bb722a7dSDimitry Andric // Example: to evaluate x^3 + 2*x^2 + 3*x + 4, call
22*bb722a7dSDimitry Andric // polyeval( x, 4.0, 3.0, 2.0, 1.0 )
23*bb722a7dSDimitry Andric
24*bb722a7dSDimitry Andric namespace LIBC_NAMESPACE_DECL {
25*bb722a7dSDimitry Andric namespace fputil {
26*bb722a7dSDimitry Andric
27*bb722a7dSDimitry Andric template <typename T>
28*bb722a7dSDimitry Andric LIBC_INLINE cpp::enable_if_t<(sizeof(T) > sizeof(void *)), T>
polyeval(const T &,const T & a0)29*bb722a7dSDimitry Andric polyeval(const T &, const T &a0) {
30*bb722a7dSDimitry Andric return a0;
31*bb722a7dSDimitry Andric }
32*bb722a7dSDimitry Andric
33*bb722a7dSDimitry Andric template <typename T>
polyeval(T,T a0)34*bb722a7dSDimitry Andric LIBC_INLINE cpp::enable_if_t<(sizeof(T) <= sizeof(void *)), T> polyeval(T,
35*bb722a7dSDimitry Andric T a0) {
36*bb722a7dSDimitry Andric return a0;
37*bb722a7dSDimitry Andric }
38*bb722a7dSDimitry Andric
39*bb722a7dSDimitry Andric template <typename T, typename... Ts>
40*bb722a7dSDimitry Andric LIBC_INLINE cpp::enable_if_t<(sizeof(T) > sizeof(void *)), T>
polyeval(const T & x,const T & a0,const Ts &...a)41*bb722a7dSDimitry Andric polyeval(const T &x, const T &a0, const Ts &...a) {
42*bb722a7dSDimitry Andric return multiply_add(x, polyeval(x, a...), a0);
43*bb722a7dSDimitry Andric }
44*bb722a7dSDimitry Andric
45*bb722a7dSDimitry Andric template <typename T, typename... Ts>
46*bb722a7dSDimitry Andric LIBC_INLINE cpp::enable_if_t<(sizeof(T) <= sizeof(void *)), T>
polyeval(T x,T a0,Ts...a)47*bb722a7dSDimitry Andric polyeval(T x, T a0, Ts... a) {
48*bb722a7dSDimitry Andric return multiply_add(x, polyeval(x, a...), a0);
49*bb722a7dSDimitry Andric }
50*bb722a7dSDimitry Andric
51*bb722a7dSDimitry Andric } // namespace fputil
52*bb722a7dSDimitry Andric } // namespace LIBC_NAMESPACE_DECL
53*bb722a7dSDimitry Andric
54*bb722a7dSDimitry Andric #endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_POLYEVAL_H
55