[SDAG] Handle LowerOperation returning its input consistently

For almost all node types, if the target requested custom lowering, and
LowerOperation returned its input, we'd treat the original node as legal. This
did not work, however, for many loads and stores, because they follow
slightly different code paths, and we did not account for the possibility of
LowerOperation returning its input at those call sites.

I think that we now handle this consistently everywhere. At the call sites in
LegalizeDAG, we used to assert in this case, so there's no functional change
for any existing code there. For the call sites in LegalizeVectorOps, this
really only affects whether or not we set Changed = true, but I think makes the
semantics clearer.

No test case here, but it will be covered by an upcoming PowerPC commit adding
QPX support.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230332 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index a26f30739c707d07f1846d4918b3e0bed4c5c79d..61c0a6fee1dc1d9dc83636dbdf56e8f600e81aa6 100644 (file)
--- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -731,7 +731,7 @@ void SelectionDAGLegalize::LegalizeStoreOps(SDNode *Node) {
         }
         case TargetLowering::Custom: {
           SDValue Res = TLI.LowerOperation(SDValue(Node, 0), DAG);
-          if (Res.getNode())
+          if (Res && Res != SDValue(Node, 0))
             ReplaceNode(SDValue(Node, 0), Res);
           return;
         }
@@ -843,7 +843,7 @@ void SelectionDAGLegalize::LegalizeStoreOps(SDNode *Node) {
         }
         case TargetLowering::Custom: {
           SDValue Res = TLI.LowerOperation(SDValue(Node, 0), DAG);
-          if (Res.getNode())
+          if (Res && Res != SDValue(Node, 0))
             ReplaceNode(SDValue(Node, 0), Res);
           return;
         }

diff --git a/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp b/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
index 9abbe738dfa04a8985d0c976004aaf352f24f300..03c2734a9e40386684da0da5af46f834a2987b66 100644 (file)
--- a/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
@@ -207,6 +207,8 @@ SDValue VectorLegalizer::LegalizeOp(SDValue Op) {
         return TranslateLegalizeResults(Op, Result);
       case TargetLowering::Custom:
         if (SDValue Lowered = TLI.LowerOperation(Result, DAG)) {
+          if (Lowered == Result)
+            return TranslateLegalizeResults(Op, Lowered);
           Changed = true;
           if (Lowered->getNumValues() != Op->getNumValues()) {
             // This expanded to something other than the load. Assume the
@@ -232,9 +234,11 @@ SDValue VectorLegalizer::LegalizeOp(SDValue Op) {
       default: llvm_unreachable("This action is not supported yet!");
       case TargetLowering::Legal:
         return TranslateLegalizeResults(Op, Result);
-      case TargetLowering::Custom:
-        Changed = true;
-        return TranslateLegalizeResults(Op, TLI.LowerOperation(Result, DAG));
+      case TargetLowering::Custom: {
+        SDValue Lowered = TLI.LowerOperation(Result, DAG);
+        Changed = Lowered != Result;
+        return TranslateLegalizeResults(Op, Lowered);
+      }
       case TargetLowering::Expand:
         Changed = true;
         return LegalizeOp(ExpandStore(Op));