More check elimination improvements including partial learning on false branches of CompareMap and …

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index ce83d901cf1387b6bdbfd5f032674c5c93bc6a58..51c3e2426789f915ed084f9fae67f573c09efa92 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -337,6 +337,15 @@ void HBasicBlock::PostProcessLoopHeader(IterationStatement* stmt) {
 }
 
 
+void HBasicBlock::MarkSuccEdgeUnreachable(int succ) {
+  ASSERT(IsFinished());
+  HBasicBlock* succ_block = end()->SuccessorAt(succ);
+
+  ASSERT(succ_block->predecessors()->length() == 1);
+  succ_block->MarkUnreachable();
+}
+
+
 void HBasicBlock::RegisterPredecessor(HBasicBlock* pred) {
   if (HasPredecessor()) {
     // Only loop header blocks can have a predecessor added after