Check elimination improvement: propagation of state through phis is supported, CheckMap narrowing i…

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 3fb867bde3d5ed6403c6ee474a2e5dca71469d1c..bc898050f00c7ad702fac60bb3c9c91f3508bf11 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -302,6 +302,12 @@ bool HBasicBlock::Dominates(HBasicBlock* other) const {
 }
 
 
+bool HBasicBlock::EqualToOrDominates(HBasicBlock* other) const {
+  if (this == other) return true;
+  return Dominates(other);
+}
+
+
 int HBasicBlock::LoopNestingDepth() const {
   const HBasicBlock* current = this;
   int result  = (current->IsLoopHeader()) ? 1 : 0;
@@ -3915,7 +3921,13 @@ void HGraph::RestoreActualValues() {
 
     for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
       HInstruction* instruction = it.Current();
-      if (instruction->ActualValue() != instruction) {
+      if (instruction->CheckFlag(HValue::kIsDead)) {
+        // The instruction was marked as deleted but left in the graph
+        // as a control flow dependency point for subsequent
+        // instructions.
+        instruction->DeleteAndReplaceWith(instruction->ActualValue());
+
+      } else if (instruction->ActualValue() != instruction) {
         ASSERT(instruction->IsInformativeDefinition());
         if (instruction->IsPurelyInformativeDefinition()) {
           instruction->DeleteAndReplaceWith(instruction->RedefinedOperand());