[interpreter] Support laziness in combination with embedded handlers

Even in the embedded bytecode handler configuration, there's currently
no guarantee that all handlers are eager. Specifically, on ia32
handlers are currently not embedded and thus lazy.

We need to keep lazy deserialization logic around until that is no
longer the case.

Bug: v8:6624
Change-Id: Ie4ec5f0fcd9890ed96a5df3bf3654e85379f92ae
Reviewed-on: https://chromium-review.googlesource.com/1236261Reviewed-by: Dan Elphick <delphick@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56110}

src/builtins/generate-bytecodes-builtins-list.cc

@@ -62,7 +62,6 @@ void WriteHeader(const char* header_filename) {
   CHECK_EQ(wide_count, extra_wide_count);
   out << "\n\nconst int kNumberOfBytecodeHandlers = " << single_count << ";\n"
       << "const int kNumberOfWideBytecodeHandlers = " << wide_count << ";\n\n"
-      << "#ifndef V8_EMBEDDED_BYTECODE_HANDLERS\n"
       << "// Mapping from (Bytecode + OperandScaleAsIndex * |Bytecodes|) to\n"
       << "// a dense form with all the illegal Bytecode/OperandScale\n"
       << "// combinations removed. Used to index into the builtins table.\n"
@@ -76,8 +75,7 @@ void WriteHeader(const char* header_filename) {
     out << offset_table[i] << ", ";
   }
 
-  out << "};\n"
-      << "#endif  //V8_EMBEDDED_BYTECODE_HANDLERS\n\n"
+  out << "};\n\n"
       << "}  // namespace internal\n"
       << "}  // namespace v8\n"
       << "#endif  // V8_BUILTINS_GENERATED_BYTECODES_BUILTINS_LIST\n";

src/interpreter/interpreter.cc

@@ -60,7 +60,6 @@ Interpreter::Interpreter(Isolate* isolate) : isolate_(isolate) {
   }
 }
 
-#ifndef V8_EMBEDDED_BYTECODE_HANDLERS
 namespace {
 
 int BuiltinIndexFromBytecode(Bytecode bytecode, OperandScale operand_scale) {
@@ -73,17 +72,9 @@ int BuiltinIndexFromBytecode(Bytecode bytecode, OperandScale operand_scale) {
 }
 
 }  // namespace
-#endif  // V8_EMBEDDED_BYTECODE_HANDLERS
 
 Code* Interpreter::GetAndMaybeDeserializeBytecodeHandler(
     Bytecode bytecode, OperandScale operand_scale) {
-#ifdef V8_EMBEDDED_BYTECODE_HANDLERS
-  size_t index = GetDispatchTableIndex(bytecode, operand_scale);
-  Address pc = dispatch_table_[index];
-  Code* builtin = InstructionStream::TryLookupCode(isolate_, pc);
-  DCHECK(builtin->IsCode());
-  return builtin;
-#else
   int builtin_index = BuiltinIndexFromBytecode(bytecode, operand_scale);
   Builtins* builtins = isolate_->builtins();
   Code* code = builtins->builtin(builtin_index);
@@ -102,7 +93,6 @@ Code* Interpreter::GetAndMaybeDeserializeBytecodeHandler(
   SetBytecodeHandler(bytecode, operand_scale, code);
 
   return code;
-#endif  // V8_EMBEDDED_BYTECODE_HANDLERS
 }
 
 void Interpreter::SetBytecodeHandler(Bytecode bytecode,