MachineScheduler: Add a way to disable the 'ReduceLatency' heuristic

llvm-svn: 251037

llvm/include/llvm/CodeGen/MachineScheduler.h

@@ -156,8 +156,12 @@ struct MachineSchedPolicy {
   bool OnlyTopDown;
   bool OnlyBottomUp;
 
+  // Disable heuristic that tries to fetch nodes from long dependency chains
+  // first.
+  bool DisableLatencyHeuristic;
+
   MachineSchedPolicy(): ShouldTrackPressure(false), OnlyTopDown(false),
-    OnlyBottomUp(false) {}
+    OnlyBottomUp(false), DisableLatencyHeuristic(false) {}
 };
 
 /// MachineSchedStrategy - Interface to the scheduling algorithm used by

llvm/lib/CodeGen/MachineScheduler.cpp

@@ -2722,8 +2722,8 @@ void GenericScheduler::tryCandidate(SchedCandidate &Cand,
 
   // Avoid serializing long latency dependence chains.
   // For acyclic path limited loops, latency was already checked above.
-  if (Cand.Policy.ReduceLatency && !Rem.IsAcyclicLatencyLimited
-      && tryLatency(TryCand, Cand, Zone)) {
+  if (!RegionPolicy.DisableLatencyHeuristic && Cand.Policy.ReduceLatency &&
+      !Rem.IsAcyclicLatencyLimited && tryLatency(TryCand, Cand, Zone)) {
     return;
   }