SSI implementation.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index bf508dac28d7aeea2af3cfa3eb5281c7d0f83513..559dcd91109a808cef72f530e9c7a54dcab2d433 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -597,6 +597,11 @@ HConstant* HGraph::GetConstantInt32(SetOncePointer<HConstant>* pointer,
 }
 
 
+HConstant* HGraph::GetConstant0() {
+  return GetConstantInt32(&constant_0_, 0);
+}
+
+
 HConstant* HGraph::GetConstant1() {
   return GetConstantInt32(&constant_1_, 1);
 }
@@ -3499,6 +3504,11 @@ bool HGraph::Optimize(SmartArrayPointer<char>* bailout_reason) {
   HStackCheckEliminator sce(this);
   sce.Process();
 
+  if (FLAG_use_ssi) {
+    BuildSsi();
+    CleanupSsi();
+  }
+
   EliminateRedundantBoundsChecks();
   DehoistSimpleArrayIndexComputations();
   if (FLAG_dead_code_elimination) DeadCodeElimination();
@@ -3939,6 +3949,28 @@ void HGraph::DehoistSimpleArrayIndexComputations() {
 }
 
 
+void HGraph::BuildSsi() {
+  HPhase phase("H_Build SSI", this);
+  entry_block()->BuildSsiRecursively();
+}
+
+
+void HGraph::CleanupSsi() {
+  HPhase phase("H_Cleanup SSI", this);
+  for (int b_index = 0; b_index < blocks()->length(); b_index++) {
+    HBasicBlock* block = blocks()->at(b_index);
+    HInstruction* current = block->first();
+    while (current != NULL) {
+      HInstruction* next = current->next();
+      if (current->IsSsiDefinition()) {
+        current->DeleteAndReplaceWith(current->ValueBeforeSsi());
+      }
+      current = next;
+    }
+  }
+}
+
+
 void HGraph::DeadCodeElimination() {
   HPhase phase("H_Dead code elimination", this);
   ZoneList<HInstruction*> worklist(blocks_.length(), zone());