MIPS: Refactor HType to get rid of various hacks.

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 48781f45b0c96674a3a28c68f4898daefa432239..333d8499c4fa2e6474f23d82116671b183c587d7 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -1925,7 +1925,9 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
 LInstruction* LChunkBuilder::DoCheckHeapObject(HCheckHeapObject* instr) {
   LOperand* value = UseRegisterAtStart(instr->value());
   LInstruction* result = new(zone()) LCheckNonSmi(value);
-  if (!instr->value()->IsHeapObject()) result = AssignEnvironment(result);
+  if (!instr->value()->type().IsHeapObject()) {
+    result = AssignEnvironment(result);
+  }
   return result;
 }