Add a hack to the scheduler to disable pseudo-two-address dependencies in

basic blocks containing calls. This works around a problem in which
these artificial dependencies can get tied up in calling seqeunce
scheduling in a way that makes the graph unschedulable with the current
approach of using artificial physical register dependencies for calling
sequences. This fixes PR11314.

llvm-svn: 144124

1 files changed, 13 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
index cab303dd5c3..f965a5e8ab5 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
@@ -1666,7 +1666,7 @@ public:
 
 protected:
   bool canClobber(const SUnit *SU, const SUnit *Op);
-  void AddPseudoTwoAddrDeps();
+  void AddPseudoTwoAddrDeps(const TargetInstrInfo *TII);
   void PrescheduleNodesWithMultipleUses();
   void CalculateSethiUllmanNumbers();
 };
@@ -2628,7 +2628,7 @@ bool ilp_ls_rr_sort::operator()(SUnit *left, SUnit *right) const {
 void RegReductionPQBase::initNodes(std::vector<SUnit> &sunits) {
   SUnits = &sunits;
   // Add pseudo dependency edges for two-address nodes.
-  AddPseudoTwoAddrDeps();
+  AddPseudoTwoAddrDeps(TII);
   // Reroute edges to nodes with multiple uses.
   if (!TracksRegPressure)
     PrescheduleNodesWithMultipleUses();
@@ -2855,7 +2855,17 @@ void RegReductionPQBase::PrescheduleNodesWithMultipleUses() {
 /// one that has a CopyToReg use (more likely to be a loop induction update).
 /// If both are two-address, but one is commutable while the other is not
 /// commutable, favor the one that's not commutable.
-void RegReductionPQBase::AddPseudoTwoAddrDeps() {
+void RegReductionPQBase::AddPseudoTwoAddrDeps(const TargetInstrInfo *TII) {
+  // If the graph contains any calls, disable this optimization.
+  // FIXME: This is a kludge to work around the fact that the artificial edges
+  // can combine with the way call sequences use physical register dependencies
+  // to model their resource usage to create unschedulable graphs.
+  for (unsigned i = 0, e = SUnits->size(); i != e; ++i)
+    for (SDNode *Node = (*SUnits)[i].getNode(); Node; Node = Node->getGluedNode())
+      if (Node->isMachineOpcode() &&
+          Node->getMachineOpcode() == (unsigned)TII->getCallFrameSetupOpcode())
+        return;
+
   for (unsigned i = 0, e = SUnits->size(); i != e; ++i) {
     SUnit *SU = &(*SUnits)[i];
     if (!SU->isTwoAddress)