Add a copied flag to virtual frame elements that tells if a copy has...

src/virtual-frame.cc

Index: src/virtual-frame.cc
===================================================================
--- src/virtual-frame.cc	(revision 1542)
+++ src/virtual-frame.cc	(working copy)
@@ -93,9 +93,11 @@
     case FrameElement::REGISTER:
       // All copies are backed by memory or register locations.
       result.type_ =
-          FrameElement::TypeField::encode(FrameElement::COPY) |
-          FrameElement::SyncField::encode(FrameElement::NOT_SYNCED);
+          FrameElement::TypeField::encode(FrameElement::COPY)
+          | FrameElement::IsCopiedField::encode(false)
+          | FrameElement::SyncField::encode(FrameElement::NOT_SYNCED);
       result.data_.index_ = index;
+      elements_[index].set_copied();
       break;
 
     case FrameElement::INVALID:
@@ -208,11 +210,15 @@
   if (!elements_[index].is_valid()) return;
 
   SyncElementAt(index);
+  // The element is now in memory.  Its copied flag is preserved.
+  FrameElement new_element = FrameElement::MemoryElement();
+  if (elements_[index].is_copied()) {
+    new_element.set_copied();
+  }
   if (elements_[index].is_register()) {
     Unuse(elements_[index].reg());
   }
-  // The element is now in memory.
-  elements_[index] = FrameElement::MemoryElement();
+  elements_[index] = new_element;
 }
 
 
@@ -276,6 +282,11 @@
       ASSERT(source.is_valid());
       elements_[i].clear_sync();
     }
+
+    elements_[i].clear_copied();
+    if (elements_[i].is_copy()) {
+      elements_[elements_[i].index()].set_copied();
+    }
   }
 }
 
@@ -367,7 +378,8 @@
 
   // If the original may be a copy, adjust to preserve the copy-on-write
   // semantics of copied elements.
-  if (original.is_register() || original.is_memory()) {
+  if (original.is_copied() &&
+      (original.is_register() || original.is_memory())) {
     FrameElement ignored = AdjustCopies(frame_index);
   }
 
@@ -523,8 +535,7 @@
 
 
 bool FrameElement::Equals(FrameElement other) {
-  if (type() != other.type()) return false;
-  if (is_synced() != other.is_synced()) return false;
+  if (type_ != other.type_) return false;
 
   if (is_register()) {
     if (!reg().is(other.reg())) return false;
@@ -539,17 +550,13 @@
 
 
 bool VirtualFrame::Equals(VirtualFrame* other) {
+#ifdef DEBUG
+  // These are sanity checks in debug builds, but we do not need to
+  // use them to distinguish frames at merge points.
   if (cgen_ != other->cgen_) return false;
   if (masm_ != other->masm_) return false;
-  if (elements_.length() != other->elements_.length()) return false;
-
-  for (int i = 0; i < elements_.length(); i++) {
-    if (!elements_[i].Equals(other->elements_[i])) return false;
-  }
-
   if (parameter_count_ != other->parameter_count_) return false;
   if (local_count_ != other->local_count_) return false;
-  if (stack_pointer_ != other->stack_pointer_) return false;
   if (frame_pointer_ != other->frame_pointer_) return false;
 
   for (int i = 0; i < kNumRegisters; i++) {
@@ -557,6 +564,12 @@
       return false;
     }
   }
+  if (elements_.length() != other->elements_.length()) return false;
+#endif
+  if (stack_pointer_ != other->stack_pointer_) return false;
+  for (int i = 0; i < elements_.length(); i++) {
+    if (!elements_[i].Equals(other->elements_[i])) return false;
+  }
 
   return true;
 }