A change in the way we place TransitionElementKinds in the tree.

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 06b021669bd1792e150796f844f135935179dbdc..909d772706d4752a51230e52fc84f65b4c55584f 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -5296,26 +5296,43 @@ void LCodeGen::EmitDeepCopy(Handle<JSObject> object,
 
 
 void LCodeGen::DoFastLiteral(LFastLiteral* instr) {
-  int size = instr->hydrogen()->total_size();
-  ElementsKind boilerplate_elements_kind =
-      instr->hydrogen()->boilerplate()->GetElementsKind();
-
-  // Deopt if the array literal boilerplate ElementsKind is of a type different
-  // than the expected one. The check isn't necessary if the boilerplate has
-  // already been converted to TERMINAL_FAST_ELEMENTS_KIND.
-  if (CanTransitionToMoreGeneralFastElementsKind(
-          boilerplate_elements_kind, true)) {
-    __ LoadHeapObject(r1, instr->hydrogen()->boilerplate());
-    // Load map into r2.
-    __ ldr(r2, FieldMemOperand(r1, HeapObject::kMapOffset));
-    // Load the map's "bit field 2".
-    __ ldrb(r2, FieldMemOperand(r2, Map::kBitField2Offset));
-    // Retrieve elements_kind from bit field 2.
-    __ ubfx(r2, r2, Map::kElementsKindShift, Map::kElementsKindBitCount);
-    __ cmp(r2, Operand(boilerplate_elements_kind));
-    DeoptimizeIf(ne, instr->environment());
+  Handle<JSObject> result = instr->hydrogen()->boilerplate();
+
+  if (instr->hydrogen()->TransitionRequested()) {
+    ElementsKind to_kind = instr->hydrogen()->TransitionTo();
+    result = Runtime::DeepCopyBoilerplate(isolate(),
+                                          instr->hydrogen()->boilerplate());
+    CHECK(!result.is_null());
+    // Now transition the copy
+    CHECK(!JSObject::TransitionElementsKind(result, to_kind).is_null());
+  } else {
+    ElementsKind boilerplate_elements_kind = result->GetElementsKind();
+
+    // Deopt if the array literal boilerplate ElementsKind is of a type
+    // different than the expected one. The check isn't necessary if the
+    // boilerplate has already been converted to TERMINAL_FAST_ELEMENTS_KIND.
+    if (CanTransitionToMoreGeneralFastElementsKind(
+            boilerplate_elements_kind, true)) {
+      __ LoadHeapObject(r1, result);
+      // Load map into r2.
+      __ ldr(r2, FieldMemOperand(r1, HeapObject::kMapOffset));
+      // Load the map's "bit field 2".
+      __ ldrb(r2, FieldMemOperand(r2, Map::kBitField2Offset));
+      // Retrieve elements_kind from bit field 2.
+      __ ubfx(r2, r2, Map::kElementsKindShift, Map::kElementsKindBitCount);
+      __ cmp(r2, Operand(boilerplate_elements_kind));
+      DeoptimizeIf(ne, instr->environment());
+    }
   }
 
+  // We need to compute the size now.
+  int size = 0;
+  int max_properties = HFastLiteral::kMaxLiteralProperties;
+  HFastLiteral::IsFastLiteral(result,
+                              HFastLiteral::kMaxLiteralDepth,
+                              &max_properties,
+                              &size);
+
   // Allocate all objects that are part of the literal in one big
   // allocation. This avoids multiple limit checks.
   Label allocated, runtime_allocate;
@@ -5329,8 +5346,8 @@ void LCodeGen::DoFastLiteral(LFastLiteral* instr) {
 
   __ bind(&allocated);
   int offset = 0;
-  __ LoadHeapObject(r1, instr->hydrogen()->boilerplate());
-  EmitDeepCopy(instr->hydrogen()->boilerplate(), r0, r1, &offset);
+  __ LoadHeapObject(r1, result);
+  EmitDeepCopy(result, r0, r1, &offset);
   ASSERT_EQ(size, offset);
 }