[Turbofan] Don't inline if we never saw a function.

Also prevent division by zero.

R=tebbi@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2731723002
Cr-Commit-Position: refs/heads/master@{#43590}

src/compiler/js-inlining-heuristic.cc

@@ -164,6 +164,10 @@ void JSInliningHeuristic::Finalize() {
     auto i = candidates_.begin();
     Candidate candidate = *i;
     candidates_.erase(i);
+    // Only include candidates that we've successfully called before.
+    // The candidate list is sorted, so we can exit at the first occurance of
+    // frequency 0 in the list.
+    if (candidate.frequency <= 0.0) return;
     // Make sure we don't try to inline dead candidate nodes.
     if (!candidate.node->IsDead()) {
       Reduction const reduction = InlineCandidate(candidate);

src/feedback-vector.cc

@@ -591,6 +591,10 @@ int CallICNexus::ExtractCallCount() {
 float CallICNexus::ComputeCallFrequency() {
   double const invocation_count = vector()->invocation_count();
   double const call_count = ExtractCallCount();
+  if (invocation_count == 0) {
+    // Prevent division by 0.
+    return 0.0f;
+  }
   return static_cast<float>(call_count / invocation_count);
 }