[compiler-rt] [ctxprof] Auto root detection: trie for stack samples (PR #133106)

[Snehasish Kumar via llvm-commits]

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@@ -0,0 +1,68 @@
+/*===- RootAutodetector.h- auto-detect roots for ctxprof  -----------------===*\
+|*
+|* 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
+|*
+\*===----------------------------------------------------------------------===*/
+
+#ifndef CTX_PROFILE_ROOTAUTODETECTOR_H_
+#define CTX_PROFILE_ROOTAUTODETECTOR_H_
+
+#include "sanitizer_common/sanitizer_dense_map.h"
+#include "sanitizer_common/sanitizer_internal_defs.h"
+#include "sanitizer_common/sanitizer_stacktrace.h"
+#include <pthread.h>
+#include <sanitizer/common_interface_defs.h>
+
+using namespace __asan;
+using namespace __sanitizer;
+
+namespace __ctx_profile {
+
+template <typename T> using Set = DenseMap<T, bool>;
+
+/// A trie. A node is the address of a callsite in a function activation. A
+/// child is a callsite in the activation made from the callsite corresponding
+/// to the parent.
+class Trie final {
+  friend class PerThreadCallsiteTrie;
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snehasish wrote:

Why do we need a friend class here?

https://github.com/llvm/llvm-project/pull/133106