[profiler] reduce incorrectly unaccounted ticks.

No longer invalidate the tick sample if there is no JS frame or only one
non-interpreted JS frame on the stack.

R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2799603005
Cr-Commit-Position: refs/heads/master@{#44465}

src/profiler/tick-sample.cc

@@ -225,12 +225,7 @@ bool TickSample::GetStackSample(Isolate* v8_isolate, RegisterState* regs,
   i::SafeStackFrameIterator it(isolate, reinterpret_cast<i::Address>(regs->fp),
                                reinterpret_cast<i::Address>(regs->sp),
                                js_entry_sp);
-
-  // If at this point iterator does not see any frames,
-  // is usually means something is wrong with the FP,
-  // e.g. it is used as a general purpose register in the function.
-  // Bailout.
-  if (it.done()) return false;
+  if (it.done()) return true;
 
   size_t i = 0;
   if (record_c_entry_frame == kIncludeCEntryFrame &&

test/cctest/cctest.status

@@ -117,6 +117,7 @@
 ['arch == arm64', {
 
   'test-cpu-profiler/CollectDeoptEvents': [PASS, FAIL],
+  'test-cpu-profiler/CollectOptimizedToplevelProfile': [PASS, FAIL],
 
   'test-api/Bug618': [PASS],
 

test/cctest/test-cpu-profiler.cc

@@ -621,6 +621,51 @@ TEST(CollectCpuProfile) {
   profile->Delete();
 }
 
+static const char* cpu_profiler_toplevel_source =
+    "for (var i = 0; i < 1E5; i++) {"
+    "  var s = 0;"
+    "  for (var j = 0; j < 1E2; j++) s += i;"
+    "}";
+
+TEST(CollectOptimizedToplevelProfile) {
+  LocalContext env;
+  v8::HandleScope scope(env->GetIsolate());
+
+  v8::CpuProfiler* profiler = v8::CpuProfiler::New(env->GetIsolate());
+  v8::Local<v8::String> profile_name = v8_str("my_profile");
+
+  profiler->SetSamplingInterval(100);
+  profiler->StartProfiling(profile_name, true);
+  v8::internal::CpuProfiler* iprofiler =
+      reinterpret_cast<v8::internal::CpuProfiler*>(profiler);
+  v8::sampler::Sampler* sampler = iprofiler->processor()->sampler();
+  sampler->StartCountingSamples();
+
+  CompileRun(cpu_profiler_toplevel_source);
+
+  v8::CpuProfile* profile = profiler->StopProfiling(profile_name);
+  reinterpret_cast<i::CpuProfile*>(profile)->Print();
+
+  const v8::CpuProfileNode* root = profile->GetTopDownRoot();
+  v8::Local<v8::String> empty = v8::String::Empty(env->GetIsolate());
+  unsigned toplevel_hitcount = 0;
+  unsigned unaccounted_hitcount = 0;
+  for (int i = 0; i < root->GetChildrenCount(); i++) {
+    const v8::CpuProfileNode* child = root->GetChild(i);
+    if (empty->Equals(env.local(), child->GetFunctionName()).FromJust()) {
+      toplevel_hitcount += child->GetHitCount();
+    } else {
+      unaccounted_hitcount += child->GetHitCount();
+    }
+  }
+  // Check that we are getting more ticks from the toplevel function than
+  // unaccounted ticks.
+  DCHECK(toplevel_hitcount > unaccounted_hitcount);
+
+  profile->Delete();
+  profiler->Dispose();
+}
+
 static const char* hot_deopt_no_frame_entry_test_source =
     "%NeverOptimizeFunction(foo);\n"
     "%NeverOptimizeFunction(start);\n"