[Interpreter] Enable tracing of bytecode handler dispatches.

src/interpreter/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/interpreter/interpreter.h"
 
 #include "src/ast/prettyprinter.h"
 #include "src/code-factory.h"
 #include "src/compiler.h"
 #include "src/factory.h"
@@ skipping 15 matching lines @@
 Interpreter::Interpreter(Isolate* isolate) : isolate_(isolate) {
   memset(dispatch_table_, 0, sizeof(dispatch_table_));
 }
 
 void Interpreter::Initialize() {
   DCHECK(FLAG_ignition);
   if (IsDispatchTableInitialized()) return;
   Zone zone(isolate_->allocator());
   HandleScope scope(isolate_);
 
+  if (FLAG_trace_ignition_dispatches) {
+    static const int kBytecodeCount = static_cast<int>(Bytecode::kLast) + 1;
+    bytecode_dispatch_count_table_.Reset(
+        new uintptr_t[kBytecodeCount * kBytecodeCount]);
+    memset(bytecode_dispatch_count_table_.get(), 0,
+           sizeof(uintptr_t) * kBytecodeCount * kBytecodeCount);
+  }
+
   // Generate bytecode handlers for all bytecodes and scales.
   for (OperandScale operand_scale = OperandScale::kSingle;
        operand_scale <= OperandScale::kMaxValid;
        operand_scale = Bytecodes::NextOperandScale(operand_scale)) {
 #define GENERATE_CODE(Name, ...)                                               \
   {                                                                            \
     if (Bytecodes::BytecodeHasHandler(Bytecode::k##Name, operand_scale)) {     \
       InterpreterAssembler assembler(isolate_, &zone, Bytecode::k##Name,       \
                                      operand_scale);                           \
       Do##Name(&assembler);                                                    \
@@ skipping 95 matching lines @@
     bytecodes->Print(os);
     os << std::flush;
   }
 
   info->SetBytecodeArray(bytecodes);
   info->SetCode(info->isolate()->builtins()->InterpreterEntryTrampoline());
   return true;
 }
 
 bool Interpreter::IsDispatchTableInitialized() {
-  if (FLAG_trace_ignition || FLAG_trace_ignition_codegen) {
-    // Regenerate table to add bytecode tracing operations
-    // or to print the assembly code generated by TurboFan.
+  if (FLAG_trace_ignition || FLAG_trace_ignition_codegen ||
+      FLAG_trace_ignition_dispatches) {
+    // Regenerate table to add bytecode tracing operations,
+    // print the assembly code generated by TurboFan,
+    // or instrument handlers with dispatch counters.
     return false;
   }
   return dispatch_table_[0] != nullptr;
 }
 
 void Interpreter::TraceCodegen(Handle<Code> code) {
 #ifdef ENABLE_DISASSEMBLER
   if (FLAG_trace_ignition_codegen) {
     OFStream os(stdout);
     code->Disassemble(nullptr, os);
@@ skipping 1450 matching lines @@
 // Illegal
 //
 // An invalid bytecode aborting execution if dispatched.
 void Interpreter::DoIllegal(InterpreterAssembler* assembler) {
   __ Abort(kInvalidBytecode);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8