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

2 files changed, 3 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Scalar/EarlyCSE.cpp b/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
index e5bbad9f73f..3707cecd014 100644
--- a/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
+++ b/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
@@ -673,7 +673,7 @@ bool EarlyCSE::processNode(DomTreeNode *Node) {
     // to advance the generation.  We do need to prevent DSE across the fence,
     // but that's handled above.
     if (FenceInst *FI = dyn_cast<FenceInst>(Inst))
-      if (FI->getOrdering() == Release) {
+      if (FI->getOrdering() == AtomicOrdering::Release) {
         assert(Inst->mayReadFromMemory() && "relied on to prevent DSE above");
         continue;
       }
diff --git a/llvm/lib/Transforms/Scalar/LowerAtomic.cpp b/llvm/lib/Transforms/Scalar/LowerAtomic.cpp
index 41511bcb7b0..47d374248dc 100644
--- a/llvm/lib/Transforms/Scalar/LowerAtomic.cpp
+++ b/llvm/lib/Transforms/Scalar/LowerAtomic.cpp
@@ -100,12 +100,12 @@ static bool LowerFenceInst(FenceInst *FI) {
 }
 
 static bool LowerLoadInst(LoadInst *LI) {
-  LI->setAtomic(NotAtomic);
+  LI->setAtomic(AtomicOrdering::NotAtomic);
   return true;
 }
 
 static bool LowerStoreInst(StoreInst *SI) {
-  SI->setAtomic(NotAtomic);
+  SI->setAtomic(AtomicOrdering::NotAtomic);
   return true;
 }