Atomic load/store on ARM/Thumb.

I don't really like the patterns, but I'm having trouble coming up with a
better way to handle them.

I plan on making other targets use the same legalization
ARM-without-memory-barriers is using... it's not especially efficient, but
if anyone cares, it's not that hard to fix for a given target if there's
some better lowering.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@138621 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 27 insertions, 5 deletions

diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 79129df..a9be49b 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -2976,6 +2976,32 @@ void SelectionDAGLegalize::ExpandNode(SDNode *Node,
     Results.push_back(CallResult.second);
     break;
   }
+  case ISD::ATOMIC_LOAD: {
+    // There is no libcall for atomic load; fake it with ATOMIC_CMP_SWAP.
+    SDValue Zero = DAG.getConstant(0, cast<AtomicSDNode>(Node)->getMemoryVT());
+    SDValue Swap = DAG.getAtomic(ISD::ATOMIC_CMP_SWAP, dl,
+                                 cast<AtomicSDNode>(Node)->getMemoryVT(),
+                                 Node->getOperand(0),
+                                 Node->getOperand(1), Zero, Zero,
+                                 cast<AtomicSDNode>(Node)->getMemOperand(),
+                                 cast<AtomicSDNode>(Node)->getOrdering(),
+                                 cast<AtomicSDNode>(Node)->getSynchScope());
+    Results.push_back(Swap.getValue(0));
+    Results.push_back(Swap.getValue(1));
+    break;
+  }
+  case ISD::ATOMIC_STORE: {
+    // There is no libcall for atomic store; fake it with ATOMIC_SWAP.
+    SDValue Swap = DAG.getAtomic(ISD::ATOMIC_SWAP, dl,
+                                 cast<AtomicSDNode>(Node)->getMemoryVT(),
+                                 Node->getOperand(0),
+                                 Node->getOperand(1), Node->getOperand(2),
+                                 cast<AtomicSDNode>(Node)->getMemOperand(),
+                                 cast<AtomicSDNode>(Node)->getOrdering(),
+                                 cast<AtomicSDNode>(Node)->getSynchScope());
+    Results.push_back(Swap.getValue(1));
+    break;
+  }
   // By default, atomic intrinsics are marked Legal and lowered. Targets
   // which don't support them directly, however, may want libcalls, in which
   // case they mark them Expand, and we get here.
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 1c28d39..0b0b98d 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3289,7 +3289,7 @@ static SDValue InsertFenceForAtomic(SDValue Chain, AtomicOrdering Order,
                                     const TargetLowering &TLI) {
   // Fence, if necessary
   if (Before) {
-    if (Order == AcquireRelease)
+    if (Order == AcquireRelease || Order == SequentiallyConsistent)
       Order = Release;
     else if (Order == Acquire || Order == Monotonic)
       return Chain;
@@ -3400,10 +3400,6 @@ void SelectionDAGBuilder::visitAtomicLoad(const LoadInst &I) {
 
   SDValue InChain = getRoot();
 
-  if (TLI.getInsertFencesForAtomic())
-    InChain = InsertFenceForAtomic(InChain, Order, Scope, true, dl,
-                                   DAG, TLI);
-
   EVT VT = EVT::getEVT(I.getType());
 
   SDValue L =