Adaptive compilation for generators

src/core/IronPython/Compiler/Ast/PythonNameBinder.cs

@@ -565,7 +565,8 @@ public override bool Walk(RaiseStatement node) {
         // ForEachStatement
         public override bool Walk(ForStatement node) {
             node.Parent = _currentScope;
-            if (_currentScope is FunctionDefinition) {
+            // generators are invoked for each item so the adaptive compiler picks up the hot ones
+            if (_currentScope is FunctionDefinition { IsGenerator: false }) {
                 _currentScope.ShouldInterpret = false;
             }
 

src/core/IronPython/Compiler/LazyCode.cs

@@ -4,16 +4,17 @@
 
 using System.Linq.Expressions;
 
+using Microsoft.Scripting.Interpreter;
 using Microsoft.Scripting.Runtime;
 
 namespace IronPython.Compiler {
     /// <summary>
     /// Represents code which can be lazily compiled.
-    /// 
-    /// The code is created in an AST which provides the Expression of T and 
+    ///
+    /// The code is created in an AST which provides the Expression of T and
     /// whether or not the code should be interpreted.  For non-pre compiled
     /// scenarios the code will not be compiled until the 1st time it is run.
-    /// 
+    ///
     /// For pre-compiled scenarios the code is IExpressionSerializable and will
     /// turn into a normal pre-compiled method.
     /// </summary>
@@ -44,7 +45,16 @@ public T EnsureDelegate() {
 
         private T Compile() {
             if (_shouldInterpret) {
-                return (T)(object)Microsoft.Scripting.Generation.CompilerHelpers.LightCompile(Code, _compilationThreshold);
+                var result = (System.Delegate)(object)Microsoft.Scripting.Generation.CompilerHelpers.LightCompile(Code, _compilationThreshold);
+
+                // If the adaptive compiler decides to compile this code, we
+                // want to store the new compiled target. This saves us from going
+                // through the interpreter stub every call.
+                if (result.Target is LightLambda lightLambda) {
+                    lightLambda.Compile += (_, e) => Delegate = (T)(object)e.Compiled;
+                }
+
+                return (T)(object)result;
             }
 
             return Code.Compile();