Avoiding overly aggressive latency scheduling. If the two nodes share an

[oota-llvm.git] / lib / CodeGen / SelectionDAG / ScheduleDAGSDNodes.cpp

diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp b/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
index d34a52d80144997a85a1d7939dbef19eb883fdc6..7d01bd31b960148517eaffc4a4f5654938ef8c47 100644 (file)
--- a/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
+++ b/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
@@ -458,6 +458,15 @@ void ScheduleDAGSDNodes::ComputeOperandLatency(SDNode *Def, SDNode *Use,
     // Adjust the use operand index by num of defs.
     OpIdx += TII->get(Use->getMachineOpcode()).getNumDefs();
   int Latency = TII->getOperandLatency(InstrItins, Def, DefIdx, Use, OpIdx);
+  if (Latency > 1 && Use->getOpcode() == ISD::CopyToReg &&
+      !BB->succ_empty()) {
+    unsigned Reg = cast<RegisterSDNode>(Use->getOperand(1))->getReg();
+    if (TargetRegisterInfo::isVirtualRegister(Reg))
+      // This copy is a liveout value. It is likely coalesced, so reduce the
+      // latency so not to penalize the def.
+      // FIXME: need target specific adjustment here?
+      Latency = (Latency > 1) ? Latency - 1 : 1;
+  }
   if (Latency >= 0)
     dep.setLatency(Latency);
 }