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diff --git a/runtime.h b/runtime.h
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+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+// -*- mode: C++ -*-
+//
+// Copyright 2021-2023 Google LLC
+//
+// Licensed under the Apache License v2.0 with LLVM Exceptions (the
+// "License"); you may not use this file except in compliance with the
+// License.  You may obtain a copy of the License at
+//
+//     https://llvm.org/LICENSE.txt
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Author: Giuliano Procida
+
+#ifndef STG_RUNTIME_H_
+#define STG_RUNTIME_H_
+
+#include <cstddef>
+#include <cstdint>
+#include <ctime>
+#include <map>
+#include <ostream>
+
+namespace stg {
+
+struct Nanoseconds {
+  explicit Nanoseconds(uint64_t ns) : ns(ns) {}
+  uint64_t ns;
+};
+
+struct Frequencies {
+  std::map<size_t, size_t> counts;
+};
+
+struct Runtime {
+  Runtime(std::ostream& output, bool print_metrics)
+      : output(output), print_metrics(print_metrics) {}
+  template <typename V>
+  void PrintMetric(const char* name, const V& value) {
+    if (print_metrics) {
+      output << name << ": " << value << '\n';
+    }
+  }
+  std::ostream& output;
+  bool print_metrics;
+};
+
+// These objects only record values on destruction, so scope them!
+
+class Time {
+ public:
+  Time(Runtime& runtime, const char* name);
+  Time(Time&& other) = delete;
+  Time& operator=(Time&& other) = delete;
+  ~Time();
+
+ private:
+  Runtime& runtime_;
+  const char* name_;
+  struct timespec start_;
+};
+
+class Counter {
+ public:
+  Counter(Runtime& runtime, const char* name);
+  Counter(Counter&& other) = delete;
+  Counter& operator=(Counter&& other) = delete;
+  ~Counter();
+
+  Counter& operator=(size_t x) {
+    value_ = x;
+    return *this;
+  }
+
+  Counter& operator+=(size_t x) {
+    value_ += x;
+    return *this;
+  }
+
+  Counter& operator++() {
+    ++value_;
+    return *this;
+  }
+
+ private:
+  Runtime& runtime_;
+  const char* name_;
+  size_t value_;
+};
+
+class Histogram {
+ public:
+  Histogram(Runtime& runtime, const char* name);
+  Histogram(Histogram&& other) = delete;
+  Histogram& operator=(Histogram&& other) = delete;
+  ~Histogram();
+
+  void Add(size_t item) {
+    ++frequencies_.counts[item];
+  }
+
+ private:
+  Runtime& runtime_;
+  const char* name_;
+  Frequencies frequencies_;
+};
+
+}  // namespace stg
+
+#endif  // STG_RUNTIME_H_