[interpreter] Add support for scalable operands.

src/runtime/runtime-interpreter.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/runtime/runtime-utils.h"
 
 #include <iomanip>
 
 #include "src/arguments.h"
 #include "src/frames-inl.h"
@@ skipping 10 matching lines @@
   DCHECK_EQ(2, args.length());
   CONVERT_ARG_HANDLE_CHECKED(SharedFunctionInfo, shared, 0);
   CONVERT_SMI_ARG_CHECKED(pretenured_flag, 1);
   Handle<Context> context(isolate->context(), isolate);
   return *isolate->factory()->NewFunctionFromSharedFunctionInfo(
       shared, context, static_cast<PretenureFlag>(pretenured_flag));
 }
 
 namespace {
 
+void AdvanceToOffsetForTracing(
+    interpreter::BytecodeArrayIterator& bytecode_iterator, int offset) {
+  if (offset > 0) {
+    uint8_t last_byte = bytecode_iterator.bytecode_array()->get(offset - 1);
+    auto maybe_bytecode = static_cast<interpreter::Bytecode>(last_byte);
+    if (interpreter::Bytecodes::IsPrefixScalingBytecode(maybe_bytecode)) {
+      // Previous byte looks like a prefix byte so scan forward slowly.
+      while (bytecode_iterator.current_offset() +
+                 bytecode_iterator.current_bytecode_size() <=
+             offset) {
+        bytecode_iterator.Advance();
+      }
+      DCHECK(bytecode_iterator.current_offset() == offset ||
+             ((bytecode_iterator.current_offset() == offset - 1) &&
+              bytecode_iterator.current_operand_scale() > 1));
+    } else {
+      bytecode_iterator.set_current_offset(offset);
+    }
+  }
+  DCHECK(bytecode_iterator.current_bytecode() != interpreter::Bytecode::kWide);
+}
+
 void PrintRegisters(std::ostream& os, bool is_input,
-                    Handle<BytecodeArray> bytecode_array, int bytecode_offset,
+                    interpreter::BytecodeArrayIterator& bytecode_iterator,
                     Handle<Object> accumulator) {
   static const int kRegFieldWidth = static_cast<int>(strlen("accumulator"));
   static const char* kInputColourCode = "\033[0;36m";
   static const char* kOutputColourCode = "\033[0;35m";
   static const char* kNormalColourCode = "\033[0;m";
   const char* kArrowDirection = is_input ? " -> " : " <- ";
   if (FLAG_log_colour) {
     os << (is_input ? kInputColourCode : kOutputColourCode);
   }
 
   // Print accumulator.
   os << "      [ accumulator" << kArrowDirection;
   accumulator->ShortPrint();
   os << " ]" << std::endl;
 
   // Find the location of the register file.
-  JavaScriptFrameIterator frame_iterator(bytecode_array->GetIsolate());
+  JavaScriptFrameIterator frame_iterator(
+      bytecode_iterator.bytecode_array()->GetIsolate());
   JavaScriptFrame* frame = frame_iterator.frame();
   Address register_file =
       frame->fp() + InterpreterFrameConstants::kRegisterFilePointerFromFp;
 
   // Print the registers.
-  interpreter::BytecodeArrayIterator bytecode_iterator(bytecode_array);
-  bytecode_iterator.set_current_offset(
-      bytecode_offset - BytecodeArray::kHeaderSize + kHeapObjectTag);
   interpreter::Bytecode bytecode = bytecode_iterator.current_bytecode();
   int operand_count = interpreter::Bytecodes::NumberOfOperands(bytecode);
   for (int operand_index = 0; operand_index < operand_count; operand_index++) {
     interpreter::OperandType operand_type =
         interpreter::Bytecodes::GetOperandType(bytecode, operand_index);
     bool should_print =
         is_input
             ? interpreter::Bytecodes::IsRegisterInputOperandType(operand_type)
             : interpreter::Bytecodes::IsRegisterOutputOperandType(operand_type);
     if (should_print) {
       interpreter::Register first_reg =
           bytecode_iterator.GetRegisterOperand(operand_index);
       int range = bytecode_iterator.GetRegisterOperandRange(operand_index);
       for (int reg_index = first_reg.index();
            reg_index < first_reg.index() + range; reg_index++) {
         Address reg_location = register_file - reg_index * kPointerSize;
         Object* reg_object = Memory::Object_at(reg_location);
         os << "      [ " << std::setw(kRegFieldWidth)
            << interpreter::Register(reg_index).ToString(
-                  bytecode_array->parameter_count())
+                  bytecode_iterator.bytecode_array()->parameter_count())
            << kArrowDirection;
         reg_object->ShortPrint(os);
         os << " ]" << std::endl;
       }
     }
   }
   if (FLAG_log_colour) {
     os << kNormalColourCode;
   }
 }
 
 }  // namespace
 
 RUNTIME_FUNCTION(Runtime_InterpreterTraceBytecodeEntry) {
   SealHandleScope shs(isolate);
   DCHECK_EQ(3, args.length());
   CONVERT_ARG_HANDLE_CHECKED(BytecodeArray, bytecode_array, 0);
   CONVERT_SMI_ARG_CHECKED(bytecode_offset, 1);
   CONVERT_ARG_HANDLE_CHECKED(Object, accumulator, 2);
   OFStream os(stdout);
 
-  // Print bytecode.
-  const uint8_t* bytecode_address =
-      reinterpret_cast<const uint8_t*>(*bytecode_array) + bytecode_offset;
-  Vector<char> buf = Vector<char>::New(50);
-  SNPrintF(buf, "%p", bytecode_address);
-  os << " -> " << buf.start() << " (" << bytecode_offset << ") : ";
-  interpreter::Bytecodes::Decode(os, bytecode_address,
-                                 bytecode_array->parameter_count());
-  os << std::endl;
+  int offset = bytecode_offset - BytecodeArray::kHeaderSize + kHeapObjectTag;
+  interpreter::BytecodeArrayIterator bytecode_iterator(bytecode_array);
+  AdvanceToOffsetForTracing(bytecode_iterator, offset);
+  if (offset == bytecode_iterator.current_offset()) {
+    // Print bytecode.
+    const uint8_t* bytecode_address =
+        reinterpret_cast<const uint8_t*>(*bytecode_array) + bytecode_offset;
+    Vector<char> buf = Vector<char>::New(50);
+    SNPrintF(buf, "%p", bytecode_address);
+    os << " -> " << buf.start() << " (" << bytecode_offset << ") : ";
+    interpreter::Bytecodes::Decode(os, bytecode_address,
+                                   bytecode_array->parameter_count());
+    os << std::endl;
+    // Print all input registers and accumulator.
+    PrintRegisters(os, true, bytecode_iterator, accumulator);
 
-  // Print all input registers and accumulator.
-  PrintRegisters(os, true, bytecode_array, bytecode_offset, accumulator);
-
-  os << std::flush;
+    os << std::flush;
+  }
   return isolate->heap()->undefined_value();
 }
 
 RUNTIME_FUNCTION(Runtime_InterpreterTraceBytecodeExit) {
   SealHandleScope shs(isolate);
   DCHECK_EQ(3, args.length());
   CONVERT_ARG_HANDLE_CHECKED(BytecodeArray, bytecode_array, 0);
   CONVERT_SMI_ARG_CHECKED(bytecode_offset, 1);
   CONVERT_ARG_HANDLE_CHECKED(Object, accumulator, 2);
-  OFStream os(stdout);
 
-  // Print all output registers and accumulator.
-  PrintRegisters(os, false, bytecode_array, bytecode_offset, accumulator);
-  os << std::flush;
+  int offset = bytecode_offset - BytecodeArray::kHeaderSize + kHeapObjectTag;
+  interpreter::BytecodeArrayIterator bytecode_iterator(bytecode_array);
+  AdvanceToOffsetForTracing(bytecode_iterator, offset);
+  if (bytecode_iterator.current_operand_scale() == 1 ||
+      offset > bytecode_iterator.current_offset()) {
+    OFStream os(stdout);
+    // Print all output registers and accumulator.
+    PrintRegisters(os, false, bytecode_iterator, accumulator);
+    os << std::flush;
+  }
   return isolate->heap()->undefined_value();
 }
 
 RUNTIME_FUNCTION(Runtime_InterpreterClearPendingMessage) {
   SealHandleScope shs(isolate);
   DCHECK_EQ(0, args.length());
   Object* message = isolate->thread_local_top()->pending_message_obj_;
   isolate->clear_pending_message();
   return message;
 }
 
 RUNTIME_FUNCTION(Runtime_InterpreterSetPendingMessage) {
   SealHandleScope shs(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(Object, message, 0);
   isolate->thread_local_top()->pending_message_obj_ = *message;
   return isolate->heap()->undefined_value();
 }
 
 }  // namespace internal
 }  // namespace v8