[crossgen2] Implement Dispose in Compilation.

_corInfoImpls elements keeps _compilation reference which keeps reference to whole table _corInfoImpls. The circular referene together with issue dotnet#12255 potentionally leads to memory leak in crossgen2 if that table is created more than once. Dispose() method clears the table and prevents memory leak.

Signed-off-by: Timur Mustafin <[email protected]>

src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/ReadyToRunCodegenCompilation.cs

@@ -23,7 +23,7 @@
 
 namespace ILCompiler
 {
-    public abstract class Compilation : ICompilation
+    public abstract class Compilation : ICompilation, IDisposable
     {
         protected readonly DependencyAnalyzerBase<NodeFactory> _dependencyGraph;
         protected readonly NodeFactory _nodeFactory;
@@ -67,6 +67,7 @@ protected Compilation(
             _methodILCache = new ILCache(ilProvider, NodeFactory.CompilationModuleGroup);
         }
 
+        public abstract void Dispose();
         public abstract void Compile(string outputFileName);
         public abstract void WriteDependencyLog(string outputFileName);
 
@@ -218,6 +219,7 @@ public interface ICompilation
     {
         void Compile(string outputFileName);
         void WriteDependencyLog(string outputFileName);
+        void Dispose();
     }
 
     public sealed class ReadyToRunCodegenCompilation : Compilation
@@ -638,5 +640,10 @@ protected override void ComputeDependencyNodeDependencies(List<DependencyNodeCor
         }
 
         public ISymbolNode GetFieldRvaData(FieldDesc field) => NodeFactory.CopiedFieldRva(field);
+
+        public override void Dispose()
+        {
+            _corInfoImpls?.Clear();
+        }
     }
 }

src/coreclr/tools/aot/crossgen2/Program.cs

@@ -632,6 +632,7 @@ private int Run(string[] args)
 
                 if (_commandLineOptions.DgmlLogFileName != null)
                     compilation.WriteDependencyLog(_commandLineOptions.DgmlLogFileName);
+                compilation.Dispose();
             }
 
             return 0;