[turbofan] support for Int64 in CheckedLoad/CheckedStore on 64-bit platforms.

src/compiler/mips/code-generator-mips.cc

Index: src/compiler/mips/code-generator-mips.cc
diff --git a/src/compiler/mips/code-generator-mips.cc b/src/compiler/mips/code-generator-mips.cc
index cdd8bdb337199456955860b100df294902cdc996..be741932d9bf902490c4751016e798a3430ac843 100644
--- a/src/compiler/mips/code-generator-mips.cc
+++ b/src/compiler/mips/code-generator-mips.cc
@@ -858,6 +858,10 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
     case kCheckedStoreFloat64:
       ASSEMBLE_CHECKED_STORE_FLOAT(Double, sdc1);
       break;
+    case kCheckedLoadWord64:
+    case kCheckedStoreWord64:
+      UNREACHABLE();  // currently unsupported checked int64 load/store.
+      break;
   }
 }