[debugger] infrastructure for side-effect-free debug-evaluate.

src/interpreter/bytecodes.cc

 // Copyright 2015 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.
 
 #include "src/interpreter/bytecodes.h"
 
 #include <iomanip>
 
 #include "src/base/bits.h"
 #include "src/interpreter/bytecode-traits.h"
@@ skipping 271 matching lines @@
   return kOperandSizes[static_cast<size_t>(operand_type)][scale_index];
 }
 
 // static
 bool Bytecodes::BytecodeHasHandler(Bytecode bytecode,
                                    OperandScale operand_scale) {
   return operand_scale == OperandScale::kSingle ||
          Bytecodes::IsBytecodeWithScalableOperands(bytecode);
 }
 
+// static
+bool Bytecodes::BytecodeIsReadOnly(Bytecode bytecode) {
+  // TODO(yangguo): whitelist more bytecodes.
+  if (IsWithoutExternalSideEffects(bytecode)) return true;
+  if (IsCallRuntime(bytecode)) return true;

[jgruber, 2017/01/10 12:46:37]

Is CallRuntime really side-effect-free? What about e.g. desugarings into runtime
calls in the parser?

+  if (IsCallOrNew(bytecode)) return true;

[jgruber, 2017/01/10 12:46:37]

This is considered side-effect-free because we re-check on calls, correct?

[Yang, 2017/01/10 14:14:06]

Yes.

+  switch (bytecode) {
+    case Bytecode::kStackCheck:
+    case Bytecode::kLdaLookupSlot:
+    case Bytecode::kLdaGlobal:
+    case Bytecode::kLdaNamedProperty:
+    case Bytecode::kLdaKeyedProperty:
+    case Bytecode::kAdd:
+    case Bytecode::kReturn:
+    case Bytecode::kCreateCatchContext:
+    case Bytecode::kSetPendingMessage:
+    case Bytecode::kPushContext:
+    case Bytecode::kPopContext:
+      return true;
+    default:
+      return false;
+  }
+}
+
 std::ostream& operator<<(std::ostream& os, const Bytecode& bytecode) {
   return os << Bytecodes::ToString(bytecode);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8