src/java.base/share/classes/java/lang/invoke/InvokerBytecodeGenerator.java

rev 15353 : 8164044: Generate corresponding simple DelegatingMethodHandles when generating a DirectMethodHandle at link time
Reviewed-by: vlivanov, mhaupt, shade

@@ -44,10 +44,11 @@
 import java.util.HashMap;
 import java.util.stream.Stream;
 
 import static java.lang.invoke.LambdaForm.*;
 import static java.lang.invoke.LambdaForm.BasicType.*;
+import static java.lang.invoke.LambdaForm.Kind.*;
 import static java.lang.invoke.MethodHandleNatives.Constants.*;
 import static java.lang.invoke.MethodHandleStatics.*;
 
 /**
  * Code generation backend for LambdaForm.

@@ -123,13 +124,19 @@
             localsMap[i] = invokerType.parameterSlotCount() - invokerType.parameterSlotDepth(i);
         }
     }
 
     /** For generating customized code for a single LambdaForm. */
-    InvokerBytecodeGenerator(String className, LambdaForm form, MethodType invokerType) {
+    private InvokerBytecodeGenerator(String className, LambdaForm form, MethodType invokerType) {
+        this(className, form.debugName, form, invokerType);
+    }
+
+    /** For generating customized code for a single LambdaForm. */
+    InvokerBytecodeGenerator(String className, String invokerName,
+            LambdaForm form, MethodType invokerType) {
         this(form, form.names.length,
-             className, form.debugName, invokerType);
+             className, invokerName, invokerType);
         // Create an array to map name indexes to locals indexes.
         Name[] names = form.names;
         for (int i = 0, index = 0; i < localsMap.length; i++) {
             localsMap[i] = index;
             if (i < names.length) {

@@ -595,14 +602,46 @@
         else if (c == MethodHandle.class)  return MH;
         assert(VerifyAccess.isTypeVisible(c, Object.class)) : c.getName();
         return c.getName().replace('.', '/');
     }
 
+    private static MemberName resolveFrom(String name, MethodType type, Class<?> holder) {
+        MemberName member = new MemberName(holder, name, type, REF_invokeStatic);
+        MemberName resolvedMember = MemberName.getFactory().resolveOrNull(REF_invokeStatic, member, holder);
+
+        return resolvedMember;
+    }
+
+    private static MemberName lookupPregenerated(LambdaForm form) {
+        if (form.customized != null) {
+            // No pre-generated version for customized LF
+            return null;
+        }
+        MethodType invokerType = form.methodType();
+        String name = form.kind.methodName;
+        switch (form.kind) {
+            case BOUND_REINVOKER: {
+                name = name + "_" + BoundMethodHandle.speciesData(form).fieldSignature();
+                return resolveFrom(name, invokerType, DelegatingMethodHandle.Holder.class);
+            }
+            case DELEGATE:                  return resolveFrom(name, invokerType, DelegatingMethodHandle.Holder.class);
+            case DIRECT_INVOKE_INTERFACE:   // fall-through
+            case DIRECT_INVOKE_SPECIAL:     // fall-through
+            case DIRECT_INVOKE_STATIC:      // fall-through
+            case DIRECT_INVOKE_STATIC_INIT: // fall-through
+            case DIRECT_INVOKE_VIRTUAL:     return resolveFrom(name, invokerType, DirectMethodHandle.Holder.class);
+        }
+        return null;
+    }
+
     /**
      * Generate customized bytecode for a given LambdaForm.
      */
     static MemberName generateCustomizedCode(LambdaForm form, MethodType invokerType) {
+        MemberName pregenerated = lookupPregenerated(form);
+        if (pregenerated != null)  return pregenerated; // pre-generated bytecode
+
         InvokerBytecodeGenerator g = new InvokerBytecodeGenerator("MH", form, invokerType);
         return g.loadMethod(g.generateCustomizedCodeBytes());
     }
 
     /** Generates code to check that actual receiver and LambdaForm matches */