IR: add a second ordering operand to cmpxhg for failure

The syntax for "cmpxchg" should now look something like:

	cmpxchg i32* %addr, i32 42, i32 3 acquire monotonic

where the second ordering argument gives the required semantics in the case
that no exchange takes place. It should be no stronger than the first ordering
constraint and cannot be either "release" or "acq_rel" (since no store will
have taken place).

rdar://problem/15996804

llvm-svn: 203559

1 files changed, 6 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 13daba08eea..b60e7803b79 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3605,14 +3605,15 @@ static SDValue InsertFenceForAtomic(SDValue Chain, AtomicOrdering Order,
 
 void SelectionDAGBuilder::visitAtomicCmpXchg(const AtomicCmpXchgInst &I) {
   SDLoc dl = getCurSDLoc();
-  AtomicOrdering Order = I.getOrdering();
+  AtomicOrdering SuccessOrder = I.getSuccessOrdering();
+  AtomicOrdering FailureOrder = I.getFailureOrdering();
   SynchronizationScope Scope = I.getSynchScope();
 
   SDValue InChain = getRoot();
 
   const TargetLowering *TLI = TM.getTargetLowering();
   if (TLI->getInsertFencesForAtomic())
-    InChain = InsertFenceForAtomic(InChain, Order, Scope, true, dl,
+    InChain = InsertFenceForAtomic(InChain, SuccessOrder, Scope, true, dl,
                                    DAG, *TLI);
 
   SDValue L =
@@ -3623,13 +3624,14 @@ void SelectionDAGBuilder::visitAtomicCmpXchg(const AtomicCmpXchgInst &I) {
                   getValue(I.getCompareOperand()),
                   getValue(I.getNewValOperand()),
                   MachinePointerInfo(I.getPointerOperand()), 0 /* Alignment */,
-                  TLI->getInsertFencesForAtomic() ? Monotonic : Order,
+                  TLI->getInsertFencesForAtomic() ? Monotonic : SuccessOrder,
+                  TLI->getInsertFencesForAtomic() ? Monotonic : FailureOrder,
                   Scope);
 
   SDValue OutChain = L.getValue(1);
 
   if (TLI->getInsertFencesForAtomic())
-    OutChain = InsertFenceForAtomic(OutChain, Order, Scope, false, dl,
+    OutChain = InsertFenceForAtomic(OutChain, SuccessOrder, Scope, false, dl,
                                     DAG, *TLI);
 
   setValue(&I, L);