mi-sched: improve the generic register pressure comparison.

Only compare pressure within the same set. When multiple sets are
affected, we prioritize the most constrained set.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189641 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 14 deletions

diff --git a/lib/CodeGen/MachineScheduler.cpp b/lib/CodeGen/MachineScheduler.cpp
index ffab5f4e66..e233d4af44 100644
--- a/lib/CodeGen/MachineScheduler.cpp
+++ b/lib/CodeGen/MachineScheduler.cpp
@@ -2182,21 +2182,19 @@ static bool tryPressure(const PressureChange &TryP,
                         ConvergingScheduler::SchedCandidate &TryCand,
                         ConvergingScheduler::SchedCandidate &Cand,
                         ConvergingScheduler::CandReason Reason) {
-  if (TryP.isValid() && CandP.isValid()) {
-    // If both candidates affect the same set, go with the smallest increase.
-    if (TryP.getPSet() == CandP.getPSet()) {
-      return tryLess(TryP.getUnitInc(), CandP.getUnitInc(), TryCand, Cand,
-                     Reason);
-    }
-    // If one candidate decreases and the other increases, go with it.
-    if (tryLess(TryP.getUnitInc() < 0, CandP.getUnitInc() < 0, TryCand, Cand,
-                Reason)) {
-      return true;
-    }
+  int TryRank = TryP.getPSetOrMax();
+  int CandRank = CandP.getPSetOrMax();
+  // If both candidates affect the same set, go with the smallest increase.
+  if (TryRank == CandRank) {
+    return tryLess(TryP.getUnitInc(), CandP.getUnitInc(), TryCand, Cand,
+                   Reason);
+  }
+  // If one candidate decreases and the other increases, go with it.
+  // Invalid candidates have UnitInc==0.
+  if (tryLess(TryP.getUnitInc() < 0, CandP.getUnitInc() < 0, TryCand, Cand,
+              Reason)) {
+    return true;
   }
-  // If TryP has lower Rank, it has a higher priority.
-  int TryRank = TryP.getRank();
-  int CandRank = CandP.getRank();
   // If the candidates are decreasing pressure, reverse priority.
   if (TryP.getUnitInc() < 0)
     std::swap(TryRank, CandRank);