[Interpreter] Add option to trace bytecode execution.

src/runtime/runtime-interpreter.cc

Index: src/runtime/runtime-interpreter.cc
diff --git a/src/runtime/runtime-interpreter.cc b/src/runtime/runtime-interpreter.cc
index 96ebe5d4d3f48cfe77ab1239e8ef0c530a1a213d..fd0c42465b2fbfa4ba161664553bf93ec34dece8 100644
--- a/src/runtime/runtime-interpreter.cc
+++ b/src/runtime/runtime-interpreter.cc
@@ -2,9 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <iomanip>
+
 #include "src/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
+#include "src/frames-inl.h"
+#include "src/frames.h"
+#include "src/interpreter/bytecode-array-iterator.h"
+#include "src/interpreter/bytecodes.h"
 #include "src/isolate-inl.h"
 
 namespace v8 {
@@ -147,5 +153,103 @@ RUNTIME_FUNCTION(Runtime_InterpreterNewClosure) {
       shared, context, static_cast<PretenureFlag>(pretenured_flag));
 }
 
+static void PrintRegisters(std::ostream& os, bool is_input,
+                           Handle<BytecodeArray> bytecode_array,
+                           int bytecode_offset, Handle<Object> accumulator) {
+  static const int kRegFieldWidth = strlen("accumulator");
+  static const char* kInputColourCode = "\033[0;36m";

[oth, 2016/01/27 15:10:09]

Suggest defaulting this to the empty string on Windows or calling a function to
change the color (on Windows it'd be SetConsoleTextAttribute).

The color coding here is terminal specific. Probably works on most modern unixen
and not suggesting adding term probing.  

[rmcilroy, 2016/01/28 16:39:51]

Done by setting the default for FLAG_log_colour based on whether it is windows
or not.

+  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());
+  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();
+  for (int operand_index = 0;
+       operand_index < interpreter::Bytecodes::NumberOfOperands(bytecode);

[oth, 2016/01/27 15:10:09]

operand_index < operand_count might be more readable. The function is a bit of a
wall of characters to the reader.

[rmcilroy, 2016/01/28 16:39:51]

Done.

+       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);

[oth, 2016/01/27 15:10:09]

The precedence here should be clear without the parens (reg_index * ...)

[rmcilroy, 2016/01/28 16:39:51]

Done.

+        Object* reg_object = Memory::Object_at(reg_location);
+        os << "      [ " << std::setw(kRegFieldWidth)
+           << interpreter::Register(reg_index).ToString(
+                  bytecode_array->parameter_count())
+           << kArrowDirection;
+        reg_object->ShortPrint(os);
+        os << " ]" << std::endl;
+      }
+    }
+  }
+  if (FLAG_log_colour) {
+    os << kNormalColourCode;
+  }
+}
+
+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;
+
+  // Print all input registers and accumulator.
+  PrintRegisters(os, true, bytecode_array, bytecode_offset, accumulator);
+
+  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;
+  return isolate->heap()->undefined_value();
+}
+
 }  // namespace internal
 }  // namespace v8