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

src/hydrogen-check-elimination.cc

Index: src/hydrogen-check-elimination.cc
diff --git a/src/hydrogen-check-elimination.cc b/src/hydrogen-check-elimination.cc
index ae11042ba1e449b3c33b2d036ca36477165142d6..96d18dc990c3113de16eb7093e5a0a43fde0b95e 100644
--- a/src/hydrogen-check-elimination.cc
+++ b/src/hydrogen-check-elimination.cc
@@ -118,6 +118,8 @@ class HCheckTable : public ZoneObject {
 
   // Global analysis: Copy state to successor block.
   HCheckTable* Copy(HBasicBlock* succ, Zone* zone) {
+    ASSERT(succ->IsReachable());
+
     HCheckTable* copy = new(phase_->zone()) HCheckTable(phase_);
     for (int i = 0; i < size_; i++) {
       HCheckTableEntry* old_entry = &entries_[i];
@@ -174,6 +176,8 @@ class HCheckTable : public ZoneObject {
 
   // Global analysis: Merge this state with the other incoming state.
   HCheckTable* Merge(HBasicBlock* succ, HCheckTable* that, Zone* zone) {
+    ASSERT(succ->IsReachable());
+
     if (that->size_ == 0) {
       // If the other state is empty, simply reset.
       size_ = 0;
@@ -311,14 +315,27 @@ class HCheckTable : public ZoneObject {
   void ReduceCompareMap(HCompareMap* instr) {
     MapSet maps = FindMaps(instr->value()->ActualValue());
     if (maps == NULL) return;
+
+    TRACE(("CompareMap for #%d at B%d ",
+        instr->value()->ActualValue()->id(), instr->block()->block_id()));
+
     if (maps->Contains(instr->map())) {
       if (maps->size() == 1) {
-        // TODO(titzer): replace with goto true branch
         INC_STAT(compares_true_);
+
+        TRACE(("replaced with goto B%d (true target)\n",
+               instr->SuccessorAt(0)->block_id()));
+
+        instr->block()->ReplaceControlWithGotoSuccessor(0);
+      } else {
+        TRACE(("can't be replaced with goto: ambiguous set of maps\n"));
       }
     } else {
-      // TODO(titzer): replace with goto false branch
       INC_STAT(compares_false_);
+      TRACE(("replaced with goto B%d (false target)\n",
+             instr->SuccessorAt(1)->block_id()));
+
+      instr->block()->ReplaceControlWithGotoSuccessor(1);
     }
   }