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..7235224df120faf9cecf18be59e7b0c3000fe4ab 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -113,6 +113,15 @@ void HBasicBlock::MarkUnreachable() {
 }
 
 
+void HBasicBlock::MarkSuccEdgeUnreachable(int succ) {
+  ASSERT(IsFinished());
+  HBasicBlock* succ_block = end()->SuccessorAt(succ);
+
+  ASSERT(succ_block->predecessors()->length() == 1);
+  succ_block->MarkUnreachable();
+}
+
+
 void HBasicBlock::AttachLoopInformation() {
   ASSERT(!IsLoopHeader());
   loop_information_ = new(zone()) HLoopInformation(this, zone());
@@ -313,6 +322,34 @@ int HBasicBlock::LoopNestingDepth() const {
 }
 
 
+void HBasicBlock::ReplaceControlWithGotoSuccessor(int succ) {
+  ASSERT(IsFinished());

[titzer, 2014/01/13 17:26:56]

I think you should go ahead and implement the general case (i.e. more than 2
successors).

[Igor Sheludko, 2014/01/14 10:41:36]

It seems that there are no instructions with more than two successors.

+  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,
+      ToBooleanStub::Types(ToBooleanStub::BOOLEAN),
+      end()->SuccessorAt(0),
+      end()->SuccessorAt(1));
+
+  int unreachable_succ = 1 - succ;
+
+  MarkSuccEdgeUnreachable(unreachable_succ);

[titzer, 2014/01/13 17:26:56]

You should go through all the "other" successors, and if they have only one
predecessor (namely this one), then mark them as unreachable. Normally they
wouldn't, since we are careful to have edge-split form, but check anyway.

[Igor Sheludko, 2014/01/14 10:41:36]

Normally they
MarkSuccEdgeUnreachable() contains an ASSERT checking that we deal with the
edge-split form.

+
+  end()->DeleteAndReplaceWith(end()->ActualValue());
+  new_branch->InsertAfter(last());
+  end_ = new_branch;
+}
+
+
 void HBasicBlock::PostProcessLoopHeader(IterationStatement* stmt) {
   ASSERT(IsLoopHeader());