Fix integer overflow in instruction scheduling. This can happen if we have

basic blocks that are so long that their size overflows a short.

Also assert that overflow does not happen in the future, as requested by Evan.

This fixes PR4401.

llvm-svn: 83159

3 files changed, 13 insertions, 12 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp
index d1930b1a2c7..7eac4d81bb8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp
@@ -134,17 +134,17 @@ void ScheduleDAGFast::Schedule() {
 /// the AvailableQueue if the count reaches zero. Also update its cycle bound.
 void ScheduleDAGFast::ReleasePred(SUnit *SU, SDep *PredEdge) {
   SUnit *PredSU = PredEdge->getSUnit();
-  --PredSU->NumSuccsLeft;
-  
+
 #ifndef NDEBUG
-  if (PredSU->NumSuccsLeft < 0) {
+  if (PredSU->NumSuccsLeft == 0) {
     errs() << "*** Scheduling failed! ***\n";
     PredSU->dump(this);
     errs() << " has been released too many times!\n";
     llvm_unreachable(0);
   }
 #endif
-  
+  --PredSU->NumSuccsLeft;
+
   // If all the node's successors are scheduled, this node is ready
   // to be scheduled. Ignore the special EntrySU node.
   if (PredSU->NumSuccsLeft == 0 && PredSU != &EntrySU) {
diff --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp
index 628a2a87ee6..f17fe23fc75 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp
@@ -108,17 +108,17 @@ void ScheduleDAGList::Schedule() {
 /// the PendingQueue if the count reaches zero. Also update its cycle bound.
 void ScheduleDAGList::ReleaseSucc(SUnit *SU, const SDep &D) {
   SUnit *SuccSU = D.getSUnit();
-  --SuccSU->NumPredsLeft;
-  
+
 #ifndef NDEBUG
-  if (SuccSU->NumPredsLeft < 0) {
+  if (SuccSU->NumPredsLeft == 0) {
     errs() << "*** Scheduling failed! ***\n";
     SuccSU->dump(this);
     errs() << " has been released too many times!\n";
     llvm_unreachable(0);
   }
 #endif
-  
+  --SuccSU->NumPredsLeft;
+
   SuccSU->setDepthToAtLeast(SU->getDepth() + D.getLatency());
   
   // If all the node's predecessors are scheduled, this node is ready
diff --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
index a9d18784608..bd6e04805f1 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
@@ -278,6 +278,7 @@ void ScheduleDAGRRList::CapturePred(SDep *PredEdge) {
       AvailableQueue->remove(PredSU);
   }
 
+  assert(PredSU->NumSuccsLeft < UINT_MAX && "NumSuccsLeft will overflow!");
   ++PredSU->NumSuccsLeft;
 }
 
@@ -824,17 +825,17 @@ void ScheduleDAGRRList::ListScheduleBottomUp() {
 /// the AvailableQueue if the count reaches zero. Also update its cycle bound.
 void ScheduleDAGRRList::ReleaseSucc(SUnit *SU, const SDep *SuccEdge) {
   SUnit *SuccSU = SuccEdge->getSUnit();
-  --SuccSU->NumPredsLeft;
-  
+
 #ifndef NDEBUG
-  if (SuccSU->NumPredsLeft < 0) {
+  if (SuccSU->NumPredsLeft == 0) {
     errs() << "*** Scheduling failed! ***\n";
     SuccSU->dump(this);
     errs() << " has been released too many times!\n";
     llvm_unreachable(0);
   }
 #endif
-  
+  --SuccSU->NumPredsLeft;
+
   // If all the node's predecessors are scheduled, this node is ready
   // to be scheduled. Ignore the special ExitSU node.
   if (SuccSU->NumPredsLeft == 0 && SuccSU != &ExitSU) {