Use weak cells in map checks in polymorphic ICs.

src/ic/mips/ic-compiler-mips.cc

Index: src/ic/mips/ic-compiler-mips.cc
diff --git a/src/ic/mips/ic-compiler-mips.cc b/src/ic/mips/ic-compiler-mips.cc
index c1e67f9ab6169eac7ba25c5bc80846c40c401d2f..fd8e6fa8e06be8dde57143cf09b6c5df7c4df602 100644
--- a/src/ic/mips/ic-compiler-mips.cc
+++ b/src/ic/mips/ic-compiler-mips.cc
@@ -57,7 +57,8 @@ Handle<Code> PropertyICCompiler::CompilePolymorphic(TypeHandleList* types,
       number_of_handled_maps++;
       // Check map and tail call if there's a match.
       // Separate compare from branch, to provide path for above JumpIfSmi().
-      __ Subu(match, map_reg, Operand(map));
+      Handle<WeakCell> cell = Map::WeakCellForMap(map);
+      __ CmpWeakValue(match, map_reg, cell);
       if (type->Is(HeapType::Number())) {
         DCHECK(!number_case.is_unused());
         __ bind(&number_case);
@@ -85,15 +86,20 @@ Handle<Code> PropertyICCompiler::CompileKeyedStorePolymorphic(
   __ JumpIfSmi(receiver(), &miss);
 
   int receiver_count = receiver_maps->length();
-  __ lw(scratch1(), FieldMemOperand(receiver(), HeapObject::kMapOffset));
+  Register map_reg = scratch1();
+  Register match = scratch2();
+  __ lw(map_reg, FieldMemOperand(receiver(), HeapObject::kMapOffset));
   for (int i = 0; i < receiver_count; ++i) {
+    Handle<WeakCell> cell = Map::WeakCellForMap(receiver_maps->at(i));
+    __ CmpWeakValue(match, map_reg, cell);
     if (transitioned_maps->at(i).is_null()) {
-      __ Jump(handler_stubs->at(i), RelocInfo::CODE_TARGET, eq, scratch1(),
-              Operand(receiver_maps->at(i)));
+      __ Jump(handler_stubs->at(i), RelocInfo::CODE_TARGET, eq, match,
+              Operand(zero_reg));
     } else {
       Label next_map;
-      __ Branch(&next_map, ne, scratch1(), Operand(receiver_maps->at(i)));
-      __ li(transition_map(), Operand(transitioned_maps->at(i)));
+      __ Branch(&next_map, ne, match, Operand(zero_reg));
+      Handle<WeakCell> cell = Map::WeakCellForMap(transitioned_maps->at(i));
+      __ LoadWeakValue(transition_map(), cell, &miss);
       __ Jump(handler_stubs->at(i), RelocInfo::CODE_TARGET);
       __ bind(&next_map);
     }