[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, 4 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index 1d961af70de..d25ea4e72eb 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -2183,6 +2183,8 @@ FastISel::createMachineMemOperandFor(const Instruction *I) const {
 
   bool IsNonTemporal = I->getMetadata(LLVMContext::MD_nontemporal) != nullptr;
   bool IsInvariant = I->getMetadata(LLVMContext::MD_invariant_load) != nullptr;
+  bool IsDereferenceable =
+      I->getMetadata(LLVMContext::MD_dereferenceable) != nullptr;
   const MDNode *Ranges = I->getMetadata(LLVMContext::MD_range);
 
   AAMDNodes AAInfo;
@@ -2197,6 +2199,8 @@ FastISel::createMachineMemOperandFor(const Instruction *I) const {
     Flags |= MachineMemOperand::MOVolatile;
   if (IsNonTemporal)
     Flags |= MachineMemOperand::MONonTemporal;
+  if (IsDereferenceable)
+    Flags |= MachineMemOperand::MODereferenceable;
   if (IsInvariant)
     Flags |= MachineMemOperand::MOInvariant;