[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

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp
index 1813fb8f59b..6de41728971 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.cpp
+++ b/llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -5684,7 +5684,9 @@ static void expandLoadStackGuard(MachineInstrBuilder &MIB,
   unsigned Reg = MIB->getOperand(0).getReg();
   const GlobalValue *GV =
       cast<GlobalValue>((*MIB->memoperands_begin())->getValue());
-  auto Flags = MachineMemOperand::MOLoad | MachineMemOperand::MOInvariant;
+  auto Flags = MachineMemOperand::MOLoad |
+               MachineMemOperand::MODereferenceable |
+               MachineMemOperand::MOInvariant;
   MachineMemOperand *MMO = MBB.getParent()->getMachineMemOperand(
       MachinePointerInfo::getGOT(*MBB.getParent()), Flags, 8, 8);
   MachineBasicBlock::iterator I = MIB.getInstr();