From f55a2101e300d1b4d420a1e71ca839e3146bdf70 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Wed, 10 Dec 2008 00:24:36 +0000
Subject: [PATCH] Update CalcLatency to work in terms of edge latencies, rather
 than node latencies. Use CalcLatency instead of manual code in
 CalculatePriorities to keep it consistent. Previously it computed slightly
 different results.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60817 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/CodeGen/LatencyPriorityQueue.h |  2 +-
 lib/CodeGen/LatencyPriorityQueue.cpp        | 31 ++++-----------------
 2 files changed, 6 insertions(+), 27 deletions(-)

diff --git a/include/llvm/CodeGen/LatencyPriorityQueue.h b/include/llvm/CodeGen/LatencyPriorityQueue.h
index f04d2ede5ac..f7eb3a62a2a 100644
--- a/include/llvm/CodeGen/LatencyPriorityQueue.h
+++ b/include/llvm/CodeGen/LatencyPriorityQueue.h
@@ -115,7 +115,7 @@ public:
 
 private:
     void CalculatePriorities();
-    int CalcLatency(const SUnit &SU);
+    void CalcLatency(const SUnit &SU);
     void AdjustPriorityOfUnscheduledPreds(SUnit *SU);
     SUnit *getSingleUnscheduledPred(SUnit *SU);
   };
diff --git a/lib/CodeGen/LatencyPriorityQueue.cpp b/lib/CodeGen/LatencyPriorityQueue.cpp
index 131da27c337..2abbf364e32 100644
--- a/lib/CodeGen/LatencyPriorityQueue.cpp
+++ b/lib/CodeGen/LatencyPriorityQueue.cpp
@@ -43,16 +43,15 @@ bool latency_sort::operator()(const SUnit *LHS, const SUnit *RHS) const {
 
 /// CalcNodePriority - Calculate the maximal path from the node to the exit.
 ///
-int LatencyPriorityQueue::CalcLatency(const SUnit &SU) {
+void LatencyPriorityQueue::CalcLatency(const SUnit &SU) {
   int &Latency = Latencies[SU.NodeNum];
   if (Latency != -1)
-    return Latency;
+    return;
 
   std::vector<const SUnit*> WorkList;
   WorkList.push_back(&SU);
   while (!WorkList.empty()) {
     const SUnit *Cur = WorkList.back();
-    unsigned CurLatency = Cur->Latency;
     bool AllDone = true;
     unsigned MaxSuccLatency = 0;
     for (SUnit::const_succ_iterator I = Cur->Succs.begin(),E = Cur->Succs.end();
@@ -62,8 +61,7 @@ int LatencyPriorityQueue::CalcLatency(const SUnit &SU) {
         AllDone = false;
         WorkList.push_back(I->getSUnit());
       } else {
-        // This assumes that there's no delay for reusing registers.
-        unsigned NewLatency = SuccLatency + CurLatency;
+        unsigned NewLatency = SuccLatency + I->getLatency();
         MaxSuccLatency = std::max(MaxSuccLatency, NewLatency);
       }
     }
@@ -72,8 +70,6 @@ int LatencyPriorityQueue::CalcLatency(const SUnit &SU) {
       WorkList.pop_back();
     }
   }
-
-  return Latency;
 }
 
 /// CalculatePriorities - Calculate priorities of all scheduling units.
@@ -82,25 +78,8 @@ void LatencyPriorityQueue::CalculatePriorities() {
   NumNodesSolelyBlocking.assign(SUnits->size(), 0);
 
   // For each node, calculate the maximal path from the node to the exit.
-  std::vector<std::pair<const SUnit*, unsigned> > WorkList;
-  for (unsigned i = 0, e = SUnits->size(); i != e; ++i) {
-    const SUnit *SU = &(*SUnits)[i];
-    if (SU->Succs.empty())
-      WorkList.push_back(std::make_pair(SU, 0U));
-  }
-
-  while (!WorkList.empty()) {
-    const SUnit *SU = WorkList.back().first;
-    unsigned SuccLat = WorkList.back().second;
-    WorkList.pop_back();
-    int &Latency = Latencies[SU->NodeNum];
-    if (Latency == -1 || (SU->Latency + SuccLat) > (unsigned)Latency) {
-      Latency = SU->Latency + SuccLat;
-      for (SUnit::const_pred_iterator I = SU->Preds.begin(),E = SU->Preds.end();
-           I != E; ++I)
-        WorkList.push_back(std::make_pair(I->getSUnit(), Latency));
-    }
-  }
+  for (unsigned i = 0, e = SUnits->size(); i != e; ++i)
+    CalcLatency((*SUnits)[i]);
 }
 
 /// getSingleUnscheduledPred - If there is exactly one unscheduled predecessor
-- 
2.34.1