Merge pull request #39395 from mavasani/FixCachingCFG

Performance fix in analyzer driver for CFG based analyzers

Author: mavasani

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

@@ -2269,8 +2269,15 @@ void executeExecutableCodeActions()
 
                                 if (!operationsToAnalyze.IsEmpty)
                                 {
-                                    executeOperationsActions(operationsToAnalyze);
-                                    executeOperationsBlockActions(operationBlocksToAnalyze, operationsToAnalyze, codeBlockActions);
+                                    try
+                                    {
+                                        executeOperationsActions(operationsToAnalyze);
+                                        executeOperationsBlockActions(operationBlocksToAnalyze, operationsToAnalyze, codeBlockActions);
+                                    }
+                                    finally
+                                    {
+                                        AnalyzerExecutor.OnOperationBlockActionsExecuted(operationBlocksToAnalyze);
+                                    }
                                 }
                             }
 

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

@@ -9,6 +9,7 @@
 using System.Runtime.CompilerServices;
 using System.Threading;
 using Microsoft.CodeAnalysis.FlowAnalysis;
+using Microsoft.CodeAnalysis.Operations;
 using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Text;
 using Roslyn.Utilities;
@@ -1913,5 +1914,22 @@ private bool IsAnalyzerSuppressedForSymbol(DiagnosticAnalyzer analyzer, ISymbol
 
             return true;
         }
+
+        public void OnOperationBlockActionsExecuted(ImmutableArray<IOperation> operationBlocks)
+        {
+            // Clear _lazyControlFlowGraphMap entries for each operation block after we have executed
+            // all analysis callbacks for the given operation blocks. This avoids holding onto them
+            // for the entire compilation lifetime.
+            // These control flow graphs are created on demand and shared between flow analysis based analyzers.
+
+            if (_lazyControlFlowGraphMap?.Count > 0)
+            {
+                foreach (var operationBlock in operationBlocks)
+                {
+                    var root = operationBlock.GetRootOperation();
+                    _lazyControlFlowGraphMap.TryRemove(root, out _);
+                }
+            }
+        }
     }
 }