[CodeGen] Split out the notions of MI invariance and MI dereferenceability.

Summary:
An IR load can be invariant, dereferenceable, neither, or both.  But
currently, MI's notion of invariance is IR-invariant &&
IR-dereferenceable.

This patch splits up the notions of invariance and dereferenceability at
the MI level.  It's NFC, so adds some probably-unnecessary
"is-dereferenceable" checks, which we can remove later if desired.

Reviewers: chandlerc, tstellarAMD

Subscribers: jholewinski, arsenm, nemanjai, llvm-commits

Differential Revision: https://reviews.llvm.org/D23371

llvm-svn: 281151

llvm/lib/CodeGen/MIRPrinter.cpp

@@ -892,6 +892,8 @@ void MIPrinter::print(const MachineMemOperand &Op) {
     OS << "volatile ";
   if (Op.isNonTemporal())
     OS << "non-temporal ";
+  if (Op.isDereferenceable())
+    OS << "dereferenceable ";
   if (Op.isInvariant())
     OS << "invariant ";
   if (Op.isLoad())