Introduce HTransitionElementsKind instruction.

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index 70ef8848167c3393c95542f6b31d5e6fc92bb9e2..24da839ab8f0d061c778e6710833d0a93f485759 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -3487,6 +3487,48 @@ void LCodeGen::DoStoreKeyedGeneric(LStoreKeyedGeneric* instr) {
 }
 
 
+void LCodeGen::DoTransitionElementsKind(LTransitionElementsKind* instr) {
+  Register object_reg = ToRegister(instr->object());
+  Register new_map_reg = ToRegister(instr->new_map_reg());
+  Register scratch = scratch0();
+
+  Handle<Map> from_map = instr->original_map();
+  Handle<Map> to_map = instr->transitioned_map();
+  ElementsKind from_kind = from_map->elements_kind();
+  ElementsKind to_kind = to_map->elements_kind();
+
+  Label not_applicable;
+  __ ldr(scratch, FieldMemOperand(object_reg, HeapObject::kMapOffset));
+  __ cmp(scratch, Operand(from_map));
+  __ b(ne, &not_applicable);
+  __ mov(new_map_reg, Operand(to_map));
+  if (from_kind == FAST_SMI_ONLY_ELEMENTS && to_kind == FAST_ELEMENTS) {
+    __ str(new_map_reg, FieldMemOperand(object_reg, HeapObject::kMapOffset));
+    // Write barrier.
+    __ RecordWriteField(object_reg, HeapObject::kMapOffset, new_map_reg,
+                        scratch, kLRHasBeenSaved, kDontSaveFPRegs);
+  } else if (from_kind == FAST_SMI_ONLY_ELEMENTS &&
+      to_kind == FAST_DOUBLE_ELEMENTS) {
+    Register fixed_object_reg = ToRegister(instr->temp_reg());
+    ASSERT(fixed_object_reg.is(r2));
+    ASSERT(new_map_reg.is(r3));
+    __ mov(fixed_object_reg, object_reg);
+    CallCode(isolate()->builtins()->TransitionElementsSmiToDouble(),
+             RelocInfo::CODE_TARGET, instr);
+  } else if (from_kind == FAST_DOUBLE_ELEMENTS && to_kind == FAST_ELEMENTS) {
+    Register fixed_object_reg = ToRegister(instr->temp_reg());
+    ASSERT(fixed_object_reg.is(r2));
+    ASSERT(new_map_reg.is(r3));
+    __ mov(fixed_object_reg, object_reg);
+    CallCode(isolate()->builtins()->TransitionElementsDoubleToObject(),
+             RelocInfo::CODE_TARGET, instr);
+  } else {
+    UNREACHABLE();
+  }
+  __ bind(&not_applicable);
+}
+
+
 void LCodeGen::DoStringAdd(LStringAdd* instr) {
   __ push(ToRegister(instr->left()));
   __ push(ToRegister(instr->right()));