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, 7 insertions, 7 deletions

diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 99046d993a8..cbaaea8bbc6 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -133,13 +133,13 @@ static unsigned GetEncodedRMWOperation(AtomicRMWInst::BinOp Op) {
 
 static unsigned GetEncodedOrdering(AtomicOrdering Ordering) {
   switch (Ordering) {
-  case NotAtomic: return bitc::ORDERING_NOTATOMIC;
-  case Unordered: return bitc::ORDERING_UNORDERED;
-  case Monotonic: return bitc::ORDERING_MONOTONIC;
-  case Acquire: return bitc::ORDERING_ACQUIRE;
-  case Release: return bitc::ORDERING_RELEASE;
-  case AcquireRelease: return bitc::ORDERING_ACQREL;
-  case SequentiallyConsistent: return bitc::ORDERING_SEQCST;
+  case AtomicOrdering::NotAtomic: return bitc::ORDERING_NOTATOMIC;
+  case AtomicOrdering::Unordered: return bitc::ORDERING_UNORDERED;
+  case AtomicOrdering::Monotonic: return bitc::ORDERING_MONOTONIC;
+  case AtomicOrdering::Acquire: return bitc::ORDERING_ACQUIRE;
+  case AtomicOrdering::Release: return bitc::ORDERING_RELEASE;
+  case AtomicOrdering::AcquireRelease: return bitc::ORDERING_ACQREL;
+  case AtomicOrdering::SequentiallyConsistent: return bitc::ORDERING_SEQCST;
   }
   llvm_unreachable("Invalid ordering");
 }