Fix a bug in SelectionDAG scheduling backtracking code: PR22304.

It can happen (by line CurSU->isPending = true; // This SU is not in
AvailableQueue right now.) that a SUnit is mark as available but is
not in the AvailableQueue. For SUnit being selected for scheduling
both conditions must be met.

This patch mainly defensively protects from invalid removing a node
from a queue. Sometimes nodes are marked isAvailable but are not in
the queue because they have been defered due to some hazard.

Patch by Pawel Bylica!

llvm-svn: 233351

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
index 8b54e6568b9..5222de1063b 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
@@ -1423,9 +1423,10 @@ SUnit *ScheduleDAGRRList::PickNodeToScheduleBottomUp() {
 
       // If one or more successors has been unscheduled, then the current
       // node is no longer available.
-      if (!TrySU->isAvailable)
+      if (!TrySU->isAvailable || !TrySU->NodeQueueId)
         CurSU = AvailableQueue->pop();
       else {
+        // Available and in AvailableQueue
         AvailableQueue->remove(TrySU);
         CurSU = TrySU;
       }