Introduce HTransitionElementsKind instruction.

src/arm/lithium-arm.cc

Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index 84959397b6515024c32e813fc98dc4fff5a8c1c2..02250349362b859eb94b6abf8e00eb6666376736 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -391,6 +391,12 @@ void LStoreKeyedGeneric::PrintDataTo(StringStream* stream) {
 }
 
 
+void LTransitionElementsKind::PrintDataTo(StringStream* stream) {
+  object()->PrintTo(stream);
+  stream->Add(" %p -> %p", *original_map(), *transitioned_map());
+}
+
+
 LChunk::LChunk(CompilationInfo* info, HGraph* graph)
     : spill_slot_count_(0),
       info_(info),
@@ -1970,6 +1976,26 @@ LInstruction* LChunkBuilder::DoStoreKeyedGeneric(HStoreKeyedGeneric* instr) {
 }
 
 
+LInstruction* LChunkBuilder::DoTransitionElementsKind(
+    HTransitionElementsKind* instr) {
+  if (instr->original_map()->elements_kind() == FAST_SMI_ONLY_ELEMENTS &&
+      instr->transitioned_map()->elements_kind() == FAST_ELEMENTS) {
+    LOperand* object = UseRegister(instr->object());
+    LOperand* new_map_reg = TempRegister();
+    LTransitionElementsKind* result =
+        new LTransitionElementsKind(object, new_map_reg, NULL);
+    return DefineSameAsFirst(result);
+  } else {
+    LOperand* object = UseFixed(instr->object(), r0);
+    LOperand* fixed_object_reg = FixedTemp(r2);
+    LOperand* new_map_reg = FixedTemp(r3);
+    LTransitionElementsKind* result =
+        new LTransitionElementsKind(object, new_map_reg, fixed_object_reg);
+    return MarkAsCall(DefineFixed(result, r0), instr);
+  }
+}
+
+
 LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
   bool needs_write_barrier = instr->NeedsWriteBarrier();