Vendor import of llvm trunk r132879:vendor/llvm/llvm-r132879

http://llvm.org/svn/llvm-project/llvm/trunk@132879

1 files changed, 17 insertions, 5 deletions

diff --git a/lib/CodeGen/PostRASchedulerList.cpp b/lib/CodeGen/PostRASchedulerList.cpp
index 60c24b710792..ba8501ff7233 100644
--- a/lib/CodeGen/PostRASchedulerList.cpp
+++ b/lib/CodeGen/PostRASchedulerList.cpp
@@ -304,7 +304,7 @@ void SchedulePostRATDList::Schedule() {
   if (AntiDepBreak != NULL) {
     unsigned Broken =
       AntiDepBreak->BreakAntiDependencies(SUnits, Begin, InsertPos,
-                                          InsertPosIndex);
+                                          InsertPosIndex, DbgValues);
 
     if (Broken != 0) {
       // We made changes. Update the dependency graph.
@@ -540,10 +540,16 @@ void SchedulePostRATDList::ReleaseSucc(SUnit *SU, SDep *SuccEdge) {
 #endif
   --SuccSU->NumPredsLeft;
 
-  // Compute how many cycles it will be before this actually becomes
-  // available.  This is the max of the start time of all predecessors plus
-  // their latencies.
-  SuccSU->setDepthToAtLeast(SU->getDepth() + SuccEdge->getLatency());
+  // Standard scheduler algorithms will recompute the depth of the successor
+  // here as such:
+  //   SuccSU->setDepthToAtLeast(SU->getDepth() + SuccEdge->getLatency());
+  //
+  // However, we lazily compute node depth instead. Note that
+  // ScheduleNodeTopDown has already updated the depth of this node which causes
+  // all descendents to be marked dirty. Setting the successor depth explicitly
+  // here would cause depth to be recomputed for all its ancestors. If the
+  // successor is not yet ready (because of a transitively redundant edge) then
+  // this causes depth computation to be quadratic in the size of the DAG.
 
   // If all the node's predecessors are scheduled, this node is ready
   // to be scheduled. Ignore the special ExitSU node.
@@ -655,6 +661,12 @@ void SchedulePostRATDList::ListScheduleTopDown() {
       ScheduleNodeTopDown(FoundSUnit, CurCycle);
       HazardRec->EmitInstruction(FoundSUnit);
       CycleHasInsts = true;
+      if (HazardRec->atIssueLimit()) {
+        DEBUG(dbgs() << "*** Max instructions per cycle " << CurCycle << '\n');
+        HazardRec->AdvanceCycle();
+        ++CurCycle;
+        CycleHasInsts = false;
+      }
     } else {
       if (CycleHasInsts) {
         DEBUG(dbgs() << "*** Finished cycle " << CurCycle << '\n');