[compiler] Make --trace-opt-verbose more useful.

When passing --trace-opt-verbose print more information about why we
decide not to optimize certain functions.

R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2800623002
Cr-Commit-Position: refs/heads/master@{#44408}

src/ic/ic.cc

@@ -437,6 +437,14 @@ void IC::OnFeedbackChanged(Isolate* isolate, JSFunction* host_function) {
     info->change_own_type_change_checksum();
     host->set_profiler_ticks(0);
   } else if (host_function->IsInterpreted()) {
+    if (FLAG_trace_opt_verbose) {
+      if (host_function->shared()->profiler_ticks() != 0) {
+        PrintF("[resetting ticks for ");
+        host_function->PrintName();
+        PrintF(" due from %d due to IC change]\n",
+               host_function->shared()->profiler_ticks());
+      }
+    }
     host_function->shared()->set_profiler_ticks(0);
   }
   isolate->runtime_profiler()->NotifyICChanged();

src/runtime-profiler.cc

@@ -402,8 +402,28 @@ OptimizationReason RuntimeProfiler::ShouldOptimizeIgnition(
     int typeinfo, generic, total, type_percentage, generic_percentage;
     GetICCounts(function, &typeinfo, &generic, &total, &type_percentage,
                 &generic_percentage);
-    if (type_percentage >= FLAG_type_info_threshold) {
-      return OptimizationReason::kSmallFunction;
+    if (type_percentage < FLAG_type_info_threshold) {
+      if (FLAG_trace_opt_verbose) {
+        PrintF("[not yet optimizing ");
+        function->PrintName();
+        PrintF(
+            ", not enough type info for small function optimization: %d/%d "
+            "(%d%%)]\n",
+            typeinfo, total, type_percentage);
+      }
+      return OptimizationReason::kDoNotOptimize;
+    }
+    return OptimizationReason::kSmallFunction;
+  } else if (FLAG_trace_opt_verbose) {
+    PrintF("[not yet optimizing ");
+    function->PrintName();
+    PrintF(", not enough ticks: %d/%d and ", ticks,
+           kProfilerTicksBeforeOptimization);
+    if (any_ic_changed_) {
+      PrintF("ICs changed]\n");
+    } else {
+      PrintF(" too large for small function optimization: %d/%d]\n",
+             shared->bytecode_array()->Size(), kMaxSizeEarlyOptIgnition);
     }
   }
   return OptimizationReason::kDoNotOptimize;