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, 10 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
index 38d87cb1c58..dad42a81068 100644
--- a/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
@@ -480,14 +480,16 @@ bool ThreadSanitizer::instrumentLoadOrStore(Instruction *I,
 static ConstantInt *createOrdering(IRBuilder<> *IRB, AtomicOrdering ord) {
   uint32_t v = 0;
   switch (ord) {
-    case NotAtomic: llvm_unreachable("unexpected atomic ordering!");
-    case Unordered:              // Fall-through.
-    case Monotonic:              v = 0; break;
-    // case Consume:                v = 1; break;  // Not specified yet.
-    case Acquire:                v = 2; break;
-    case Release:                v = 3; break;
-    case AcquireRelease:         v = 4; break;
-    case SequentiallyConsistent: v = 5; break;
+    case AtomicOrdering::NotAtomic:
+      llvm_unreachable("unexpected atomic ordering!");
+    case AtomicOrdering::Unordered:              // Fall-through.
+    case AtomicOrdering::Monotonic:              v = 0; break;
+    // Not specified yet:
+    // case AtomicOrdering::Consume:                v = 1; break;
+    case AtomicOrdering::Acquire:                v = 2; break;
+    case AtomicOrdering::Release:                v = 3; break;
+    case AtomicOrdering::AcquireRelease:         v = 4; break;
+    case AtomicOrdering::SequentiallyConsistent: v = 5; break;
   }
   return IRB->getInt32(v);
 }