[ScheduleDAGRRList] Do not preschedule the node has ADJCALLSTACKDOWN parent

We should not pre-scheduled the node has ADJCALLSTACKDOWN parent,
or else, when bottom-up scheduling, ADJCALLSTACKDOWN and
ADJCALLSTACKUP may hold CallResource too long and make other
calls can't be scheduled. If there's no other available node
to schedule, the scheduler will try to rename the register by
creating copy to avoid the conflict which will fail because
CallResource is not a real physical register.

llvm-svn: 351527

1 files changed, 23 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
index 8d75b8133a3..5bb9add43c4 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
@@ -2939,6 +2939,29 @@ void RegReductionPQBase::PrescheduleNodesWithMultipleUses() {
             (cast<RegisterSDNode>(N->getOperand(1))->getReg()))
         continue;
 
+    SDNode *PredFrameSetup = nullptr;
+    for (const SDep &Pred : SU.Preds)
+      if (Pred.isCtrl() && Pred.getSUnit()) {
+        // Find the predecessor which is not data dependence.
+        SDNode *PredND = Pred.getSUnit()->getNode();
+
+        // If PredND is FrameSetup, we should not pre-scheduled the node,
+        // or else, when bottom up scheduling, ADJCALLSTACKDOWN and
+        // ADJCALLSTACKUP may hold CallResource too long and make other
+        // calls can't be scheduled. If there's no other available node
+        // to schedule, the schedular will try to rename the register by
+        // creating copy to avoid the conflict which will fail because
+        // CallResource is not a real physical register.
+        if (PredND && PredND->isMachineOpcode() &&
+            (PredND->getMachineOpcode() == TII->getCallFrameSetupOpcode())) {
+          PredFrameSetup = PredND;
+          break;
+        }
+      }
+    // Skip the node has FrameSetup parent.
+    if (PredFrameSetup != nullptr)
+      continue;
+
     // Locate the single data predecessor.
     SUnit *PredSU = nullptr;
     for (const SDep &Pred : SU.Preds)