NFC: make AtomicOrdering an enum class

Summary:
In the context of http://wg21.link/lwg2445 C++ uses the concept of
'stronger' ordering but doesn't define it properly. This should be fixed
in C++17 barring a small question that's still open.

The code currently plays fast and loose with the AtomicOrdering
enum. Using an enum class is one step towards tightening things. I later
also want to tighten related enums, such as clang's
AtomicOrderingKind (which should be shared with LLVM as a 'C++ ABI'
enum).

This change touches a few lines of code which can be improved later, I'd
like to keep it as NFC for now as it's already quite complex. I have
related changes for clang.

As a follow-up I'll add:
  bool operator<(AtomicOrdering, AtomicOrdering) = delete;
  bool operator>(AtomicOrdering, AtomicOrdering) = delete;
  bool operator<=(AtomicOrdering, AtomicOrdering) = delete;
  bool operator>=(AtomicOrdering, AtomicOrdering) = delete;
This is separate so that clang and LLVM changes don't need to be in sync.

Reviewers: jyknight, reames

Subscribers: jyknight, llvm-commits

Differential Revision: http://reviews.llvm.org/D18775

llvm-svn: 265602

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/IR/Instruction.cpp b/llvm/lib/IR/Instruction.cpp
index 4b33d2e66ea..e2b5e2777fa 100644
--- a/llvm/lib/IR/Instruction.cpp
+++ b/llvm/lib/IR/Instruction.cpp
@@ -461,9 +461,9 @@ bool Instruction::isAtomic() const {
   case Instruction::Fence:
     return true;
   case Instruction::Load:
-    return cast<LoadInst>(this)->getOrdering() != NotAtomic;
+    return cast<LoadInst>(this)->getOrdering() != AtomicOrdering::NotAtomic;
   case Instruction::Store:
-    return cast<StoreInst>(this)->getOrdering() != NotAtomic;
+    return cast<StoreInst>(this)->getOrdering() != AtomicOrdering::NotAtomic;
   }
 }