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, 8 deletions

diff --git a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
index ce6519a..e23cd81 100644
--- a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -93,7 +93,7 @@ static ModRefInfo GetLocation(const Instruction *Inst, MemoryLocation &Loc,
       Loc = MemoryLocation::get(LI);
       return MRI_Ref;
     }
-    if (LI->getOrdering() == Monotonic) {
+    if (LI->getOrdering() == AtomicOrdering::Monotonic) {
       Loc = MemoryLocation::get(LI);
       return MRI_ModRef;
     }
@@ -106,7 +106,7 @@ static ModRefInfo GetLocation(const Instruction *Inst, MemoryLocation &Loc,
       Loc = MemoryLocation::get(SI);
       return MRI_Mod;
     }
-    if (SI->getOrdering() == Monotonic) {
+    if (SI->getOrdering() == AtomicOrdering::Monotonic) {
       Loc = MemoryLocation::get(SI);
       return MRI_ModRef;
     }
@@ -518,11 +518,11 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
       // A Monotonic (or higher) load is OK if the query inst is itself not
       // atomic.
       // FIXME: This is overly conservative.
-      if (LI->isAtomic() && LI->getOrdering() > Unordered) {
+      if (LI->isAtomic() && isStrongerThanUnordered(LI->getOrdering())) {
         if (!QueryInst || isNonSimpleLoadOrStore(QueryInst) ||
             isOtherMemAccess(QueryInst))
           return MemDepResult::getClobber(LI);
-        if (LI->getOrdering() != Monotonic)
+        if (LI->getOrdering() != AtomicOrdering::Monotonic)
           return MemDepResult::getClobber(LI);
       }
 
@@ -588,7 +588,7 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
         if (!QueryInst || isNonSimpleLoadOrStore(QueryInst) ||
             isOtherMemAccess(QueryInst))
           return MemDepResult::getClobber(SI);
-        if (SI->getOrdering() != Monotonic)
+        if (SI->getOrdering() != AtomicOrdering::Monotonic)
           return MemDepResult::getClobber(SI);
       }
 
@@ -644,9 +644,9 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
     // loads.  DSE uses this to find preceeding stores to delete and thus we
     // can't bypass the fence if the query instruction is a store.
     if (FenceInst *FI = dyn_cast<FenceInst>(Inst))
-      if (isLoad && FI->getOrdering() == Release)
+      if (isLoad && FI->getOrdering() == AtomicOrdering::Release)
         continue;
-    
+
     // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
     ModRefInfo MR = AA.getModRefInfo(Inst, MemLoc);
     // If necessary, perform additional analysis.
@@ -1708,4 +1708,3 @@ bool MemoryDependenceWrapperPass::runOnFunction(Function &F) {
   MemDep.emplace(AA, AC, TLI, DT);
   return false;
 }
-