Eliminatable CheckMaps replaced with if(true) or if(false).

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 90f9c3496b2b4c6853419d218ae96fab4c637820..b1d28b0f0407745c775789e95310eaf3191084d3 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -313,6 +313,34 @@ int HBasicBlock::LoopNestingDepth() const {
 }
 
 
+void HBasicBlock::ReplaceControlWithGotoSuccessor(int succ) {
+  ASSERT(IsFinished());
+  ASSERT(end()->SuccessorCount() == 2);  // Only this case is supported yet.
+  ASSERT(succ < end()->SuccessorCount());
+
+  // Replace control instruction with if(true) or if(false).
+  HConstant* value = (succ == 0)
+      ? graph()->GetConstantTrue()
+      : graph()->GetConstantFalse();
+
+  HBranch* new_branch = HBranch::New(
+      zone(),
+      NULL,
+      value,

[titzer, 2014/01/14 13:40:32]

Why not always if(true) {succ} else {1 - succ}?

[Igor Sheludko, 2014/01/14 15:28:00]

Done.

+      ToBooleanStub::Types(ToBooleanStub::BOOLEAN),
+      end()->SuccessorAt(0),
+      end()->SuccessorAt(1));
+
+  int unreachable_succ = 1 - succ;
+
+  MarkSuccEdgeUnreachable(unreachable_succ);
+
+  end()->DeleteAndReplaceWith(end()->ActualValue());
+  new_branch->InsertAfter(last());
+  end_ = new_branch;
+}
+
+
 void HBasicBlock::PostProcessLoopHeader(IterationStatement* stmt) {
   ASSERT(IsLoopHeader());
 
@@ -331,6 +359,15 @@ 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