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

src/arm64/builtins-arm64.cc

Index: src/arm64/builtins-arm64.cc
diff --git a/src/arm64/builtins-arm64.cc b/src/arm64/builtins-arm64.cc
index 38bf7999f81b661dd8e4fb1f81ecad6cefa33545..8e4568e84a3362221bb00e3eedd232800c3162d6 100644
--- a/src/arm64/builtins-arm64.cc
+++ b/src/arm64/builtins-arm64.cc
@@ -872,8 +872,15 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
   // Get the bytecode array from the function object and load the pointer to the
   // first entry into kInterpreterBytecodeRegister.
   __ Ldr(x0, FieldMemOperand(x1, JSFunction::kSharedFunctionInfoOffset));
+  Register debug_info = kInterpreterBytecodeArrayRegister;
+  Label load_debug_bytecode_array, bytecode_array_loaded;
+  DCHECK(!debug_info.is(x0));
+  __ Ldr(debug_info, FieldMemOperand(x0, SharedFunctionInfo::kDebugInfoOffset));
+  __ Cmp(debug_info, Operand(DebugInfo::uninitialized()));
+  __ B(ne, &load_debug_bytecode_array);
   __ Ldr(kInterpreterBytecodeArrayRegister,
          FieldMemOperand(x0, SharedFunctionInfo::kFunctionDataOffset));
+  __ Bind(&bytecode_array_loaded);
 
   if (FLAG_debug_code) {
     // Check function data field is actually a BytecodeArray object.
@@ -944,6 +951,12 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
 
   // Even though the first bytecode handler was called, we will never return.
   __ Abort(kUnexpectedReturnFromBytecodeHandler);
+
+  // Load debug copy of the bytecode array.
+  __ Bind(&load_debug_bytecode_array);
+  __ Ldr(kInterpreterBytecodeArrayRegister,
+         FieldMemOperand(debug_info, DebugInfo::kAbstractCodeIndex));
+  __ B(&bytecode_array_loaded);
 }