[mips] Save a copy of MipsABIInfo in the MipsTargetStreamer to escape…

… a dangling pointer

The MipsTargetELFStreamer can receive ABI info from many sources. For example,
from the MipsAsmParser instance. Lifetime of the MipsAsmParser can be shorter
than MipsTargetELFStreamer's lifetime. In that case we get a dangling pointer
to MipsABIInfo.

Differential Revision: http://reviews.llvm.org/D12805

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247546 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Mips/MipsTargetStreamer.h

@@ -12,6 +12,7 @@
 
 #include "MCTargetDesc/MipsABIFlagsSection.h"
 #include "MCTargetDesc/MipsABIInfo.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/MC/MCELFStreamer.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCStreamer.h"
@@ -97,18 +98,18 @@ class MipsTargetStreamer : public MCTargetStreamer {
   // structure values.
   template <class PredicateLibrary>
   void updateABIInfo(const PredicateLibrary &P) {
-    ABI = &P.getABI();
+    ABI = P.getABI();
     ABIFlagsSection.setAllFromPredicates(P);
   }
 
   MipsABIFlagsSection &getABIFlagsSection() { return ABIFlagsSection; }
   const MipsABIInfo &getABI() const {
-    assert(ABI && "ABI hasn't been set!");
+    assert(ABI.hasValue() && "ABI hasn't been set!");
     return *ABI;
   }
 
 protected:
-  const MipsABIInfo *ABI;
+  llvm::Optional<MipsABIInfo> ABI;
   MipsABIFlagsSection ABIFlagsSection;
 
   bool GPRInfoSet;