Replace PooledStopwatch with SharedStopwatch

src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerExecutor.cs

@@ -1448,10 +1448,10 @@ private void ExecuteAndCatchIfThrows_NoLock<TArg>(DiagnosticAnalyzer analyzer, A
             {
                 _cancellationToken.ThrowIfCancellationRequested();
 
-                PooledStopwatch timer = null;
+                SharedStopwatch timer = default;
                 if (_analyzerExecutionTimeMapOpt != null)
                 {
-                    timer = PooledStopwatch.StartInstance();
+                    timer = SharedStopwatch.StartNew();
 
                     // This call to Restart isn't required by the API, but is included to avoid measurement errors which
                     // can occur during periods of high allocation activity. In some cases, calls to Stopwatch
@@ -1468,12 +1468,11 @@ private void ExecuteAndCatchIfThrows_NoLock<TArg>(DiagnosticAnalyzer analyzer, A
 
                 analyze(argument);
 
-                if (timer != null)
+                if (_analyzerExecutionTimeMapOpt != null)
                 {
-                    timer.Stop();
+                    var elapsed = timer.Elapsed.Ticks;
                     StrongBox<long> totalTicks = _analyzerExecutionTimeMapOpt.GetOrAdd(analyzer, _ => new StrongBox<long>(0));
-                    Interlocked.Add(ref totalTicks.Value, timer.Elapsed.Ticks);
-                    timer.Free();
+                    Interlocked.Add(ref totalTicks.Value, elapsed);
                 }
             }
             catch (Exception e) when (ExceptionFilter(e))

src/Compilers/Core/Portable/InternalUtilities/SharedStopwatch.cs

@@ -0,0 +1,67 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+
+namespace Roslyn.Utilities
+{
+    internal struct SharedStopwatch
+    {
+        private static readonly Stopwatch s_stopwatch = Stopwatch.StartNew();
+
+        private TimeSpan _accumulated;
+        private TimeSpan _started;
+
+        public readonly TimeSpan Elapsed
+        {
+            get
+            {
+                if (IsRunning)
+                    return _accumulated + s_stopwatch.Elapsed - _started;
+
+                return _accumulated;
+            }
+        }
+
+        public readonly long ElapsedMilliseconds => (long)Elapsed.TotalMilliseconds;
+        public readonly bool IsRunning => _started != TimeSpan.Zero;
+
+        public static SharedStopwatch StartNew()
+        {
+            var result = new SharedStopwatch();
+            result.Start();
+            return result;
+        }
+
+        public void Reset()
+        {
+            Stop();
+            _accumulated = TimeSpan.Zero;
+        }
+
+        public void Restart()
+        {
+            Reset();
+            Start();
+        }
+
+        public void Start()
+        {
+            if (!IsRunning)
+            {
+                _started = s_stopwatch.Elapsed;
+            }
+        }
+
+        public void Stop()
+        {
+            if (IsRunning)
+            {
+                _accumulated += s_stopwatch.Elapsed - _started;
+                _started = TimeSpan.Zero;
+            }
+        }
+    }
+}

src/Dependencies/PooledObjects/Microsoft.CodeAnalysis.PooledObjects.projitems

@@ -15,7 +15,6 @@
     <Compile Include="$(MSBuildThisFileDirectory)ObjectPool`1.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)PooledDictionary.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)PooledHashSet.cs" />
-    <Compile Include="$(MSBuildThisFileDirectory)PooledStopwatch.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)PooledStringBuilder.cs" />
   </ItemGroup>
 </Project>

src/Workspaces/Core/Portable/Microsoft.CodeAnalysis.Workspaces.csproj

@@ -27,6 +27,7 @@
   <ItemGroup Label="Linked Files">
     <Compile Remove="Storage\Sqlite\**\*.cs" Condition="'$(DotNetBuildFromSource)' == 'true'" />
     <Compile Include="..\..\..\CodeStyle\Core\CodeFixes\FixAllContextHelper.cs" Link="CodeFixes\FixAllOccurrences\FixAllContextHelper.cs" />
+    <Compile Include="..\..\..\Compilers\Core\Portable\InternalUtilities\SharedStopwatch.cs" Link="InternalUtilities\SharedStopwatch.cs" />
     <Compile Include="..\..\..\Compilers\Shared\DesktopAnalyzerAssemblyLoader.cs">
       <Link>Execution\Desktop\DesktopAnalyzerAssemblyLoader.cs</Link>
     </Compile>