[interpreter, debugger] support debug breaks via bytecode array copy

src/interpreter/interpreter-assembler.cc

Index: src/interpreter/interpreter-assembler.cc
diff --git a/src/interpreter/interpreter-assembler.cc b/src/interpreter/interpreter-assembler.cc
index 50894ab5e65cf072c6b7bf7a09fa340ad1b838be..a53408e882e178558be9b4f5e0e505755d9f29ed 100644
--- a/src/interpreter/interpreter-assembler.cc
+++ b/src/interpreter/interpreter-assembler.cc
@@ -408,9 +408,6 @@ void InterpreterAssembler::Dispatch() {
 }
 
 void InterpreterAssembler::DispatchTo(Node* new_bytecode_offset) {
-  if (FLAG_trace_ignition) {
-    TraceBytecode(Runtime::kInterpreterTraceBytecodeExit);
-  }
   Node* target_bytecode = Load(
       MachineType::Uint8(), BytecodeArrayTaggedPointer(), new_bytecode_offset);
 
@@ -420,24 +417,28 @@ void InterpreterAssembler::DispatchTo(Node* new_bytecode_offset) {
       Load(MachineType::Pointer(), DispatchTableRawPointer(),
            Word32Shl(target_bytecode, Int32Constant(kPointerSizeLog2)));
 
-  InterpreterDispatchDescriptor descriptor(isolate());
-  Node* args[] = {GetAccumulator(),          RegisterFileRawPointer(),
-                  new_bytecode_offset,       BytecodeArrayTaggedPointer(),
-                  DispatchTableRawPointer(), GetContext()};
-  TailCall(descriptor, target_code_object, args, 0);
+  DispatchToBytecodeHandler(target_code_object, new_bytecode_offset);
 }
 
-void InterpreterAssembler::InterpreterReturn() {
+void InterpreterAssembler::DispatchToBytecodeHandler(Node* handler,
+                                                     Node* bytecode_offset) {
   if (FLAG_trace_ignition) {
     TraceBytecode(Runtime::kInterpreterTraceBytecodeExit);
   }
+
+  if (bytecode_offset == nullptr) bytecode_offset = BytecodeOffset();

[rmcilroy, 2016/02/19 14:47:16]

Could you avoid this and the default argument type and just pass
BytecodeOffset() explicitly where necessary please (either make BytecodeOffset
public or add a 1 arg variant of DispatchToBytecodeHandler which calls this one
with BytecodeOffset() as the second arg).

+
   InterpreterDispatchDescriptor descriptor(isolate());
-  Node* exit_trampoline_code_object =
-      HeapConstant(isolate()->builtins()->InterpreterExitTrampoline());
   Node* args[] = {GetAccumulator(),          RegisterFileRawPointer(),
-                  BytecodeOffset(),          BytecodeArrayTaggedPointer(),
+                  bytecode_offset,           BytecodeArrayTaggedPointer(),
                   DispatchTableRawPointer(), GetContext()};
-  TailCall(descriptor, exit_trampoline_code_object, args, 0);
+  TailCall(descriptor, handler, args, 0);
+}
+
+void InterpreterAssembler::InterpreterReturn() {
+  Node* exit_trampoline_code_object =
+      HeapConstant(isolate()->builtins()->InterpreterExitTrampoline());
+  DispatchToBytecodeHandler(exit_trampoline_code_object);
 }
 
 void InterpreterAssembler::StackCheck() {