Introduce HTransitionElementsKind instruction.

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index 9e1fd34af3347c4ffbfe6fb4df1496094859a8fb..2b3929d470d49a43b1e5015f2b336e3d6d2ab681 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -3303,6 +3303,48 @@ 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());
+
+  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;
+  __ cmp(FieldOperand(object_reg, HeapObject::kMapOffset), from_map);
+  __ j(not_equal, &not_applicable);
+  __ mov(new_map_reg, to_map);
+  if (from_kind == FAST_SMI_ONLY_ELEMENTS && to_kind == FAST_ELEMENTS) {
+    Register object_reg = ToRegister(instr->object());
+    __ mov(FieldOperand(object_reg, HeapObject::kMapOffset), new_map_reg);
+    // Write barrier.
+    ASSERT_NE(instr->temp_reg(), NULL);
+    __ RecordWriteField(object_reg, HeapObject::kMapOffset, new_map_reg,
+                        ToRegister(instr->temp_reg()), 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(edx));
+    ASSERT(new_map_reg.is(ebx));
+    __ 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(edx));
+    ASSERT(new_map_reg.is(ebx));
+    __ mov(fixed_object_reg, object_reg);
+    CallCode(isolate()->builtins()->TransitionElementsDoubleToObject(),
+             RelocInfo::CODE_TARGET, instr);
+  } else {
+    UNREACHABLE();
+  }
+  __ bind(&not_applicable);
+}
+
+
 void LCodeGen::DoStringCharCodeAt(LStringCharCodeAt* instr) {
   class DeferredStringCharCodeAt: public LDeferredCode {
    public: