[llvm] [ADT] Introduce EytzingerTableSpan (PR #208885)

[Kazu Hirata via llvm-commits]

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@@ -0,0 +1,68 @@
+//===- Eytzinger.h - Eytzinger Search Tree Span -----------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file defines the EytzingerTableSpan class, a non-owning view of a
+/// buffer formatted as a complete binary search tree in Eytzinger
+/// (breadth-first) order.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_EYTZINGER_H
+#define LLVM_ADT_EYTZINGER_H
+
+#include "llvm/ADT/bit.h"
+#include <cassert>
+#include <cstddef>
+#include <optional>
+
+namespace llvm {
+
+/// Non-owning view of a buffer formatted as a complete binary search tree in
+/// Eytzinger (breadth-first) order.
+template <typename T> class EytzingerTableSpan {
+public:
+  EytzingerTableSpan() = default;
+  EytzingerTableSpan(const T *Data, size_t NumEntries)
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kazutakahirata wrote:

I've added a `isSorted` method.

https://github.com/llvm/llvm-project/pull/208885