[turbofan] Add performance counters for speculation mode change

Bug: v8:7127, v8:7216
Change-Id: I57f8bc3f486c53b11475bd174961c4547bb07b04
Reviewed-on: https://chromium-review.googlesource.com/827073
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Michael Hablich <hablich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50121}

src/counters.h

@@ -1088,7 +1088,9 @@ class RuntimeCallTimerScope {
      20)                                                                       \
   HR(wasm_lazy_compilation_throughput, V8.WasmLazyCompilationThroughput, 1,    \
      10000, 50)                                                                \
-  HR(compile_script_cache_behaviour, V8.CompileScript.CacheBehaviour, 0, 19, 20)
+  HR(compile_script_cache_behaviour, V8.CompileScript.CacheBehaviour, 0, 19,   \
+     20)                                                                       \
+  HR(speculation_mode_change, V8.SpeculationModeChange, 0, 1, 2)
 
 #define HISTOGRAM_TIMER_LIST(HT)                                               \
   /* Garbage collection timers. */                                             \

src/deoptimizer.cc

@@ -3860,8 +3860,13 @@ void TranslatedState::DoUpdateFeedback() {
   if (!feedback_vector_handle_.is_null()) {
     CHECK(!feedback_slot_.IsInvalid());
     isolate()->CountUsage(v8::Isolate::kDeoptimizerDisableSpeculation);
+    isolate()->counters()->speculation_mode_change()->AddSample(
+        static_cast<int>(SpeculationModeChange::kSetSpeculationDisallow));
     CallICNexus nexus(feedback_vector_handle_, feedback_slot_);
     nexus.SetSpeculationMode(SpeculationMode::kDisallowSpeculation);
+  } else {
+    isolate()->counters()->speculation_mode_change()->AddSample(
+        static_cast<int>(SpeculationModeChange::kNoSpeculationModeChange));
   }
 }
 

src/deoptimizer.h

@@ -1041,6 +1041,11 @@ class DeoptimizedFrameInfo : public Malloced {
   friend class Deoptimizer;
 };
 
+enum class SpeculationModeChange {
+  kNoSpeculationModeChange = 0,
+  kSetSpeculationDisallow = 1
+};
+
 }  // namespace internal
 }  // namespace v8