Add a non-const subtarget returning function to the target machine

so that we can use it to get the old-style JIT out of the subtarget.

This code should be removed when the old-style JIT is removed
(imminently).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214560 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Mips/MipsTargetMachine.h

@@ -50,13 +50,18 @@ public:
       return Subtarget;
     return &DefaultSubtarget;
   }
+  MipsSubtarget *getSubtargetImpl() override {
+    if (Subtarget)
+      return Subtarget;
+    return &DefaultSubtarget;
+  }
   const InstrItineraryData *getInstrItineraryData() const override {
     return Subtarget->inMips16Mode()
                ? nullptr
                : &getSubtargetImpl()->getInstrItineraryData();
   }
   MipsJITInfo *getJITInfo() override {
-    return Subtarget->getJITInfo();
+    return getSubtargetImpl()->getJITInfo();
   }
   const MipsRegisterInfo *getRegisterInfo()  const override {
     return getSubtargetImpl()->getRegisterInfo();