Enable optimizing JSFunctions that are in new-space.

It avoids strange performance behavior where hot functions do not
get optimized if there is no GC to promote them, and it does not seem
to hurt us otherwise.

Review URL: http://codereview.chromium.org/6594073

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7016 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.cc

@@ -844,8 +844,6 @@ void Heap::MarkCompactPrologue(bool is_compacting) {
   ContextSlotCache::Clear();
   DescriptorLookupCache::Clear();
 
-  RuntimeProfiler::MarkCompactPrologue(is_compacting);
-
   CompilationCache::MarkCompactPrologue();
 
   CompletelyClearInstanceofCache();
@@ -1056,20 +1054,13 @@ void Heap::Scavenge() {
   // Scavenge object reachable from the global contexts list directly.
   scavenge_visitor.VisitPointer(BitCast<Object**>(&global_contexts_list_));
 
-  // Scavenge objects reachable from the runtime-profiler sampler
-  // window directly.
-  Object** sampler_window_address = RuntimeProfiler::SamplerWindowAddress();
-  int sampler_window_size = RuntimeProfiler::SamplerWindowSize();
-  scavenge_visitor.VisitPointers(
-      sampler_window_address,
-      sampler_window_address + sampler_window_size);
-
   new_space_front = DoScavenge(&scavenge_visitor, new_space_front);
 
   UpdateNewSpaceReferencesInExternalStringTable(
       &UpdateNewSpaceReferenceInExternalStringTableEntry);
 
   LiveObjectList::UpdateReferencesForScavengeGC();
+  RuntimeProfiler::UpdateSamplesAfterScavenge();
 
   ASSERT(new_space_front == new_space_.top());
 

src/mark-compact.cc

@@ -1353,6 +1353,9 @@ void MarkCompactCollector::MarkLiveObjects() {
 
   // Flush code from collected candidates.
   FlushCode::ProcessCandidates();
+
+  // Clean up dead objects from the runtime profiler.
+  RuntimeProfiler::RemoveDeadSamples();
 }
 
 
@@ -1937,6 +1940,9 @@ static void SweepNewSpace(NewSpace* space) {
   // All pointers were updated. Update auxiliary allocation info.
   Heap::IncrementYoungSurvivorsCounter(survivors_size);
   space->set_age_mark(space->top());
+
+  // Update JSFunction pointers from the runtime profiler.
+  RuntimeProfiler::UpdateSamplesAfterScavenge();
 }
 
 
@@ -2535,6 +2541,7 @@ void MarkCompactCollector::UpdatePointers() {
   state_ = UPDATE_POINTERS;
 #endif
   UpdatingVisitor updating_visitor;
+  RuntimeProfiler::UpdateSamplesAfterCompact(&updating_visitor);
   Heap::IterateRoots(&updating_visitor, VISIT_ONLY_STRONG);
   GlobalHandles::IterateWeakRoots(&updating_visitor);
 

src/runtime-profiler.cc

@@ -35,6 +35,7 @@
 #include "deoptimizer.h"
 #include "execution.h"
 #include "global-handles.h"
+#include "mark-compact.h"
 #include "scopeinfo.h"
 #include "top.h"
 
@@ -100,11 +101,6 @@ static int sampler_ticks_until_threshold_adjustment =
 // The ratio of ticks spent in JS code in percent.
 static Atomic32 js_ratio;
 
-// The JSFunctions in the sampler window are not GC safe. Old-space
-// pointers are not cleared during mark-sweep collection and therefore
-// the window might contain stale pointers. The window is updated on
-// scavenges and (parts of it) cleared on mark-sweep and
-// mark-sweep-compact.
 static Object* sampler_window[kSamplerWindowSize] = { NULL, };
 static int sampler_window_position = 0;
 static int sampler_window_weight[kSamplerWindowSize] = { 0, };
@@ -134,7 +130,6 @@ void PendingListNode::WeakCallback(v8::Persistent<v8::Value>, void* data) {
 
 
 static bool IsOptimizable(JSFunction* function) {
-  if (Heap::InNewSpace(function)) return false;
   Code* code = function->code();
   return code->kind() == Code::FUNCTION && code->optimizable();
 }
@@ -208,16 +203,6 @@ static void ClearSampleBuffer() {
 }
 
 
-static void ClearSampleBufferNewSpaceEntries() {
-  for (int i = 0; i < kSamplerWindowSize; i++) {
-    if (Heap::InNewSpace(sampler_window[i])) {
-      sampler_window[i] = NULL;
-      sampler_window_weight[i] = 0;
-    }
-  }
-}
-
-
 static int LookupSample(JSFunction* function) {
   int weight = 0;
   for (int i = 0; i < kSamplerWindowSize; i++) {
@@ -372,24 +357,6 @@ void RuntimeProfiler::NotifyTick() {
 }
 
 
-void RuntimeProfiler::MarkCompactPrologue(bool is_compacting) {
-  if (is_compacting) {
-    // Clear all samples before mark-sweep-compact because every
-    // function might move.
-    ClearSampleBuffer();
-  } else {
-    // Clear only new space entries on mark-sweep since none of the
-    // old-space functions will move.
-    ClearSampleBufferNewSpaceEntries();
-  }
-}
-
-
-bool IsEqual(void* first, void* second) {
-  return first == second;
-}
-
-
 void RuntimeProfiler::Setup() {
   ClearSampleBuffer();
   // If the ticker hasn't already started, make sure to do so to get
@@ -411,13 +378,41 @@ void RuntimeProfiler::TearDown() {
 }
 
 
-Object** RuntimeProfiler::SamplerWindowAddress() {
-  return sampler_window;
+int RuntimeProfiler::SamplerWindowSize() {
+  return kSamplerWindowSize;
 }
 
 
-int RuntimeProfiler::SamplerWindowSize() {
-  return kSamplerWindowSize;
+// Update the pointers in the sampler window after a GC.
+void RuntimeProfiler::UpdateSamplesAfterScavenge() {
+  for (int i = 0; i < kSamplerWindowSize; i++) {
+    Object* function = sampler_window[i];
+    if (function != NULL && Heap::InNewSpace(function)) {
+      MapWord map_word = HeapObject::cast(function)->map_word();
+      if (map_word.IsForwardingAddress()) {
+        sampler_window[i] = map_word.ToForwardingAddress();
+      } else {
+        sampler_window[i] = NULL;
+      }
+    }
+  }
+}
+
+
+void RuntimeProfiler::RemoveDeadSamples() {
+  for (int i = 0; i < kSamplerWindowSize; i++) {
+    Object* function = sampler_window[i];
+    if (function != NULL && !HeapObject::cast(function)->IsMarked()) {
+      sampler_window[i] = NULL;
+    }
+  }
+}
+
+
+void RuntimeProfiler::UpdateSamplesAfterCompact(ObjectVisitor* visitor) {
+  for (int i = 0; i < kSamplerWindowSize; i++) {
+    visitor->VisitPointer(&sampler_window[i]);
+  }
 }
 
 

src/runtime-profiler.h

@@ -47,9 +47,10 @@ class RuntimeProfiler : public AllStatic {
   static void Reset();
   static void TearDown();
 
-  static void MarkCompactPrologue(bool is_compacting);
-  static Object** SamplerWindowAddress();
   static int SamplerWindowSize();
+  static void UpdateSamplesAfterScavenge();
+  static void RemoveDeadSamples();
+  static void UpdateSamplesAfterCompact(ObjectVisitor* visitor);
 };