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

src/x64/builtins-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/code-factory.h"
 #include "src/codegen.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 476 matching lines @@
   FrameScope frame_scope(masm, StackFrame::MANUAL);
   __ pushq(rbp);  // Caller's frame pointer.
   __ movp(rbp, rsp);
   __ Push(rsi);  // Callee's context.
   __ Push(rdi);  // Callee's JS function.
   __ Push(rdx);  // Callee's new target.
 
   // Get the bytecode array from the function object and load the pointer to the
   // first entry into edi (InterpreterBytecodeRegister).
   __ movp(rax, FieldOperand(rdi, JSFunction::kSharedFunctionInfoOffset));
+
+  Label load_debug_bytecode_array, bytecode_array_loaded;
+  __ cmpp(FieldOperand(rax, SharedFunctionInfo::kDebugInfoOffset),
+          Immediate(DebugInfo::uninitialized()));
+  __ j(not_equal, &load_debug_bytecode_array);
   __ movp(kInterpreterBytecodeArrayRegister,
           FieldOperand(rax, SharedFunctionInfo::kFunctionDataOffset));
+  __ bind(&bytecode_array_loaded);
 
   if (FLAG_debug_code) {
     // Check function data field is actually a BytecodeArray object.
     __ AssertNotSmi(kInterpreterBytecodeArrayRegister);
     __ CmpObjectType(kInterpreterBytecodeArrayRegister, BYTECODE_ARRAY_TYPE,
                      rax);
     __ Assert(equal, kFunctionDataShouldBeBytecodeArrayOnInterpreterEntry);
   }
 
   // Push bytecode array.
@@ skipping 53 matching lines @@
                           kInterpreterBytecodeOffsetRegister, times_1, 0));
   __ movp(rbx, Operand(kInterpreterDispatchTableRegister, rbx,
                        times_pointer_size, 0));
   // TODO(rmcilroy): Make dispatch table point to code entrys to avoid untagging
   // and header removal.
   __ addp(rbx, Immediate(Code::kHeaderSize - kHeapObjectTag));
   __ call(rbx);
 
   // 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);
+  Register debug_info = kInterpreterBytecodeArrayRegister;
+  __ movp(debug_info, FieldOperand(rax, SharedFunctionInfo::kDebugInfoOffset));
+  __ movp(kInterpreterBytecodeArrayRegister,
+          FieldOperand(debug_info, DebugInfo::kAbstractCodeIndex));
+  __ jmp(&bytecode_array_loaded);
 }
 
 
 void Builtins::Generate_InterpreterExitTrampoline(MacroAssembler* masm) {
   // TODO(rmcilroy): List of things not currently dealt with here but done in
   // fullcodegen's EmitReturnSequence.
   //  - Supporting FLAG_trace for Runtime::TraceExit.
   //  - Support profiler (specifically decrementing profiling_counter
   //    appropriately and calling out to HandleInterrupts if necessary).
 
@@ skipping 2145 matching lines @@
   __ ret(0);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64