MIPS: Assign less environments.

src/mips/lithium-mips.cc

Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index 2247e7c3ef0f2af28d9b92e09b9b5a8698fc31e0..be3279f575e160c15092f2e86ec61437f400d652 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -2229,10 +2229,11 @@ LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
   LOperand* temp = needs_write_barrier_for_map ? TempRegister() : NULL;
 
   LStoreNamedField* result = new(zone()) LStoreNamedField(obj, val, temp);
-  if ((FLAG_track_fields && instr->field_representation().IsSmi()) ||
-      (FLAG_track_heap_object_fields &&
-       instr->field_representation().IsHeapObject())) {
-    return AssignEnvironment(result);
+  if (FLAG_track_heap_object_fields &&
+      instr->field_representation().IsHeapObject()) {
+    if (!instr->value()->type().IsHeapObject()) {
+      return AssignEnvironment(result);
+    }
   }
   return result;
 }