[llvm] [AMDGPU][NewInsertWaitcnt] Add Event Tracker (PR #226970)

[Matt Arsenault via llvm-commits]

================
@@ -0,0 +1,354 @@
+//===- AMDGPUEventTracking.h ------------------------------------*- 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 Tracks a per-InstCounterType event timeline which preserves
+/// information about previously encountered MachineInstr and HWEvents.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_AMDGPU_UTILS_AMDGPUEVENTTRACKING_H
+#define LLVM_LIB_TARGET_AMDGPU_UTILS_AMDGPUEVENTTRACKING_H
+
+#include "AMDGPUHWEvents.h"
+#include "AMDGPUWaitcntUtils.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Twine.h"
+#include <memory>
+
+namespace llvm {
+class raw_ostream;
+class MachineBasicBlock;
+class MachineOperand;
+class MachineFunction;
+
+namespace AMDGPU {
+namespace eventtracking {
----------------
arsenm wrote:

Is this namespace really necessary 

https://github.com/llvm/llvm-project/pull/226970