MIPS: Swap bitfield3 and backpointer.

Port r12034 (f17b84c0)

Original commit message:
Bitfield3 now has its own field, while the backpointer shares the field with the descriptor array; which will become the transition array.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/10692192
Patch from Akos Palfi <palfia@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12075 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/full-codegen-mips.cc

@@ -1148,7 +1148,7 @@ void FullCodeGenerator::VisitForInStatement(ForInStatement* stmt) {
 
   // We got a map in register v0. Get the enumeration cache from it.
   __ bind(&use_cache);
-  __ LoadInstanceDescriptors(v0, a1);
+  __ LoadInstanceDescriptors(v0, a1, a2);
   __ lw(a1, FieldMemOperand(a1, DescriptorArray::kEnumerationIndexOffset));
   __ lw(a2, FieldMemOperand(a1, DescriptorArray::kEnumCacheBridgeCacheOffset));
 
@@ -2759,7 +2759,7 @@ void FullCodeGenerator::EmitIsStringWrapperSafeForDefaultValueOf(
   // Look for valueOf symbol in the descriptor array, and indicate false if
   // found. The type is not checked, so if it is a transition it is a false
   // negative.
-  __ LoadInstanceDescriptors(a1, t0);
+  __ LoadInstanceDescriptors(a1, t0, a3);
   __ lw(a3, FieldMemOperand(t0, FixedArray::kLengthOffset));
   // t0: descriptor array
   // a3: length of descriptor array

src/mips/lithium-codegen-mips.cc

@@ -5165,7 +5165,8 @@ void LCodeGen::DoForInPrepareMap(LForInPrepareMap* instr) {
 void LCodeGen::DoForInCacheArray(LForInCacheArray* instr) {
   Register map = ToRegister(instr->map());
   Register result = ToRegister(instr->result());
-  __ LoadInstanceDescriptors(map, result);
+  Register scratch = ToRegister(instr->scratch());
+  __ LoadInstanceDescriptors(map, result, scratch);
   __ lw(result,
         FieldMemOperand(result, DescriptorArray::kEnumerationIndexOffset));
   __ lw(result,

src/mips/lithium-mips.cc

@@ -2200,8 +2200,9 @@ LInstruction* LChunkBuilder::DoForInPrepareMap(HForInPrepareMap* instr) {
 
 LInstruction* LChunkBuilder::DoForInCacheArray(HForInCacheArray* instr) {
   LOperand* map = UseRegister(instr->map());
+  LOperand* scratch = TempRegister();
   return AssignEnvironment(DefineAsRegister(
-      new(zone()) LForInCacheArray(map)));
+      new(zone()) LForInCacheArray(map, scratch)));
 }
 
 

src/mips/lithium-mips.h

@@ -2143,13 +2143,15 @@ class LForInPrepareMap: public LTemplateInstruction<1, 1, 0> {
 };
 
 
-class LForInCacheArray: public LTemplateInstruction<1, 1, 0> {
+class LForInCacheArray: public LTemplateInstruction<1, 1, 1> {
  public:
-  explicit LForInCacheArray(LOperand* map) {
+  explicit LForInCacheArray(LOperand* map, LOperand* scratch) {
     inputs_[0] = map;
+    temps_[0] = scratch;
   }
 
   LOperand* map() { return inputs_[0]; }
+  LOperand* scratch() { return temps_[0]; }
 
   DECLARE_CONCRETE_INSTRUCTION(ForInCacheArray, "for-in-cache-array")
 

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

src/mips/macro-assembler-mips.h

@@ -1396,7 +1396,9 @@ class MacroAssembler: public Assembler {
                           DoubleRegister temp_double_reg);
 
 
-  void LoadInstanceDescriptors(Register map, Register descriptors);
+  void LoadInstanceDescriptors(Register map,
+                               Register descriptors,
+                               Register scratch);
 
 
   // Activation support.