MIPS: Swap bitfield3 and backpointer.

src/mips/macro-assembler-mips.cc

Index: src/mips/macro-assembler-mips.cc
diff --git a/src/mips/macro-assembler-mips.cc b/src/mips/macro-assembler-mips.cc
index 1a6bc216ccc9d72c5e060249a9ec1bd42f8396eb..6233b830e01107ec939a74441dbf15057b0a67d3 100644
--- a/src/mips/macro-assembler-mips.cc
+++ b/src/mips/macro-assembler-mips.cc
@@ -5290,13 +5290,21 @@ void MacroAssembler::EnsureNotWhite(
 
 
 void MacroAssembler::LoadInstanceDescriptors(Register map,
-                                             Register descriptors) {
+                                             Register descriptors,
+                                             Register scratch) {
   lw(descriptors,
-     FieldMemOperand(map, Map::kInstanceDescriptorsOrBitField3Offset));
-  Label not_smi;
-  JumpIfNotSmi(descriptors, &not_smi);
+     FieldMemOperand(map, Map::kInstanceDescriptorsOrBackPointerOffset));
+
+  Label ok, fail;
+  CheckMap(descriptors,
+           scratch,
+           isolate()->factory()->fixed_array_map(),
+           &fail,
+           DONT_DO_SMI_CHECK);
+  jmp(&ok);
+  bind(&fail);
   LoadRoot(descriptors, Heap::kEmptyDescriptorArrayRootIndex);
-  bind(&not_smi);
+  bind(&ok);
 }
 
 
@@ -5320,8 +5328,13 @@ void MacroAssembler::CheckEnumCache(Register null_value, Label* call_runtime) {
   // check for an enum cache.  Leave the map in a2 for the subsequent
   // prototype load.
   lw(a2, FieldMemOperand(a1, HeapObject::kMapOffset));
-  lw(a3, FieldMemOperand(a2, Map::kInstanceDescriptorsOrBitField3Offset));
-  JumpIfSmi(a3, call_runtime);
+  lw(a3, FieldMemOperand(a2, Map::kInstanceDescriptorsOrBackPointerOffset));
+
+  CheckMap(a3,
+           t3,
+           isolate()->factory()->fixed_array_map(),
+           call_runtime,
+           DONT_DO_SMI_CHECK);
 
   // Check that there is an enum cache in the non-empty instance
   // descriptors (a3).  This is the case if the next enumeration