Check in LLVM r95781.
diff --git a/lib/CodeGen/LatencyPriorityQueue.cpp b/lib/CodeGen/LatencyPriorityQueue.cpp
new file mode 100644
index 0000000..f1bd573
--- /dev/null
+++ b/lib/CodeGen/LatencyPriorityQueue.cpp
@@ -0,0 +1,116 @@
+//===---- LatencyPriorityQueue.cpp - A latency-oriented priority queue ----===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the LatencyPriorityQueue class, which is a
+// SchedulingPriorityQueue that schedules using latency information to
+// reduce the length of the critical path through the basic block.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "scheduler"
+#include "llvm/CodeGen/LatencyPriorityQueue.h"
+#include "llvm/Support/Debug.h"
+using namespace llvm;
+
+bool latency_sort::operator()(const SUnit *LHS, const SUnit *RHS) const {
+ // The isScheduleHigh flag allows nodes with wraparound dependencies that
+ // cannot easily be modeled as edges with latencies to be scheduled as
+ // soon as possible in a top-down schedule.
+ if (LHS->isScheduleHigh && !RHS->isScheduleHigh)
+ return false;
+ if (!LHS->isScheduleHigh && RHS->isScheduleHigh)
+ return true;
+
+ unsigned LHSNum = LHS->NodeNum;
+ unsigned RHSNum = RHS->NodeNum;
+
+ // The most important heuristic is scheduling the critical path.
+ unsigned LHSLatency = PQ->getLatency(LHSNum);
+ unsigned RHSLatency = PQ->getLatency(RHSNum);
+ if (LHSLatency < RHSLatency) return true;
+ if (LHSLatency > RHSLatency) return false;
+
+ // After that, if two nodes have identical latencies, look to see if one will
+ // unblock more other nodes than the other.
+ unsigned LHSBlocked = PQ->getNumSolelyBlockNodes(LHSNum);
+ unsigned RHSBlocked = PQ->getNumSolelyBlockNodes(RHSNum);
+ if (LHSBlocked < RHSBlocked) return true;
+ if (LHSBlocked > RHSBlocked) return false;
+
+ // Finally, just to provide a stable ordering, use the node number as a
+ // deciding factor.
+ return LHSNum < RHSNum;
+}
+
+
+/// getSingleUnscheduledPred - If there is exactly one unscheduled predecessor
+/// of SU, return it, otherwise return null.
+SUnit *LatencyPriorityQueue::getSingleUnscheduledPred(SUnit *SU) {
+ SUnit *OnlyAvailablePred = 0;
+ for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
+ I != E; ++I) {
+ SUnit &Pred = *I->getSUnit();
+ if (!Pred.isScheduled) {
+ // We found an available, but not scheduled, predecessor. If it's the
+ // only one we have found, keep track of it... otherwise give up.
+ if (OnlyAvailablePred && OnlyAvailablePred != &Pred)
+ return 0;
+ OnlyAvailablePred = &Pred;
+ }
+ }
+
+ return OnlyAvailablePred;
+}
+
+void LatencyPriorityQueue::push_impl(SUnit *SU) {
+ // Look at all of the successors of this node. Count the number of nodes that
+ // this node is the sole unscheduled node for.
+ unsigned NumNodesBlocking = 0;
+ for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
+ I != E; ++I) {
+ if (getSingleUnscheduledPred(I->getSUnit()) == SU)
+ ++NumNodesBlocking;
+ }
+ NumNodesSolelyBlocking[SU->NodeNum] = NumNodesBlocking;
+
+ Queue.push(SU);
+}
+
+
+// ScheduledNode - As nodes are scheduled, we look to see if there are any
+// successor nodes that have a single unscheduled predecessor. If so, that
+// single predecessor has a higher priority, since scheduling it will make
+// the node available.
+void LatencyPriorityQueue::ScheduledNode(SUnit *SU) {
+ for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
+ I != E; ++I) {
+ AdjustPriorityOfUnscheduledPreds(I->getSUnit());
+ }
+}
+
+/// AdjustPriorityOfUnscheduledPreds - One of the predecessors of SU was just
+/// scheduled. If SU is not itself available, then there is at least one
+/// predecessor node that has not been scheduled yet. If SU has exactly ONE
+/// unscheduled predecessor, we want to increase its priority: it getting
+/// scheduled will make this node available, so it is better than some other
+/// node of the same priority that will not make a node available.
+void LatencyPriorityQueue::AdjustPriorityOfUnscheduledPreds(SUnit *SU) {
+ if (SU->isAvailable) return; // All preds scheduled.
+
+ SUnit *OnlyAvailablePred = getSingleUnscheduledPred(SU);
+ if (OnlyAvailablePred == 0 || !OnlyAvailablePred->isAvailable) return;
+
+ // Okay, we found a single predecessor that is available, but not scheduled.
+ // Since it is available, it must be in the priority queue. First remove it.
+ remove(OnlyAvailablePred);
+
+ // Reinsert the node into the priority queue, which recomputes its
+ // NumNodesSolelyBlocking value.
+ push(OnlyAvailablePred);
+}