Flow engine fixes: unreachable block processing, state merging.

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..8025ff1de8eae0702fe16ef9dbfc1daffeb9f7f0 100644
--- a/src/hydrogen-check-elimination.cc
+++ b/src/hydrogen-check-elimination.cc
@@ -117,7 +117,7 @@ class HCheckTable : public ZoneObject {
   }
 
   // Global analysis: Copy state to successor block.
-  HCheckTable* Copy(HBasicBlock* succ, Zone* zone) {
+  HCheckTable* Copy(HBasicBlock* succ, HBasicBlock* from_block, Zone* zone) {
     HCheckTable* copy = new(phase_->zone()) HCheckTable(phase_);
     for (int i = 0; i < size_; i++) {
       HCheckTableEntry* old_entry = &entries_[i];
@@ -173,12 +173,13 @@ class HCheckTable : public ZoneObject {
   }
 
   // Global analysis: Merge this state with the other incoming state.
-  HCheckTable* Merge(HBasicBlock* succ, HCheckTable* that, Zone* zone) {
+  void Merge(HBasicBlock* succ, HCheckTable* that,

[titzer, 2014/01/27 12:42:32]

Please keep the interface that it returns the "new" state. The idea being that
some implementations of state might be immutable (e.g. we planned on using this
for escape analysis as well).

[Igor Sheludko, 2014/01/28 16:55:42]

Done.

+             HBasicBlock* that_block, Zone* zone) {
     if (that->size_ == 0) {
       // If the other state is empty, simply reset.
       size_ = 0;
       cursor_ = 0;
-      return this;
+      return;
     }
     bool compact = false;
     for (int i = 0; i < size_; i++) {
@@ -195,7 +196,6 @@ class HCheckTable : public ZoneObject {
       }
     }
     if (compact) Compact();
-    return this;
   }
 
   void ReduceCheckMaps(HCheckMaps* instr) {