[Interpreter] Add dispatch counters for each bytecode.

src/interpreter/interpreter.cc

Index: src/interpreter/interpreter.cc
diff --git a/src/interpreter/interpreter.cc b/src/interpreter/interpreter.cc
index 5084300dfee60294b3af19832d026410b5834c6f..2543a2503e3a66def7cadd13b665a410486d31d4 100644
--- a/src/interpreter/interpreter.cc
+++ b/src/interpreter/interpreter.cc
@@ -33,6 +33,12 @@ void Interpreter::Initialize() {
   Zone zone(isolate_->allocator());
   HandleScope scope(isolate_);
 
+  if (FLAG_trace_ignition_dispatches) {
+    handlers_dispatch_counters_.Reset(new uintptr_t[kCountersTableRowSize]);
+    memset(handlers_dispatch_counters_.get(), 0,
+           sizeof(uintptr_t) * kCountersTableRowSize);
+  }
+
   // Generate bytecode handlers for all bytecodes and scales.
   for (OperandScale operand_scale = OperandScale::kSingle;
        operand_scale <= OperandScale::kMaxValid;
@@ -148,9 +154,11 @@ bool Interpreter::MakeBytecode(CompilationInfo* info) {
 }
 
 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;