1 files changed, 17 insertions, 9 deletions

diff --git a/contrib/llvm/lib/CodeGen/ScoreboardHazardRecognizer.cpp b/contrib/llvm/lib/CodeGen/ScoreboardHazardRecognizer.cpp
index 3d22035..e675366 100644
--- a/contrib/llvm/lib/CodeGen/ScoreboardHazardRecognizer.cpp
+++ b/contrib/llvm/lib/CodeGen/ScoreboardHazardRecognizer.cpp
@@ -39,13 +39,11 @@ ScoreboardHazardRecognizer(const InstrItineraryData *II,
   DebugType = ParentDebugType;
 #endif
 
-  // Determine the maximum depth of any itinerary. This determines the
-  // depth of the scoreboard. We always make the scoreboard at least 1
-  // cycle deep to avoid dealing with the boundary condition.
+  // Determine the maximum depth of any itinerary. This determines the depth of
+  // the scoreboard. We always make the scoreboard at least 1 cycle deep to
+  // avoid dealing with the boundary condition.
   unsigned ScoreboardDepth = 1;
   if (ItinData && !ItinData->isEmpty()) {
-    IssueWidth = ItinData->IssueWidth;
-
     for (unsigned idx = 0; ; ++idx) {
       if (ItinData->isEndMarker(idx))
         break;
@@ -63,16 +61,26 @@ ScoreboardHazardRecognizer(const InstrItineraryData *II,
       // Find the next power-of-2 >= ItinDepth
       while (ItinDepth > ScoreboardDepth) {
         ScoreboardDepth *= 2;
+        // Don't set MaxLookAhead until we find at least one nonzero stage.
+        // This way, an itinerary with no stages has MaxLookAhead==0, which
+        // completely bypasses the scoreboard hazard logic.
+        MaxLookAhead = ScoreboardDepth;
       }
     }
-    MaxLookAhead = ScoreboardDepth;
   }
 
   ReservedScoreboard.reset(ScoreboardDepth);
   RequiredScoreboard.reset(ScoreboardDepth);
 
-  DEBUG(dbgs() << "Using scoreboard hazard recognizer: Depth = "
-               << ScoreboardDepth << '\n');
+  // If MaxLookAhead is not set above, then we are not enabled.
+  if (!isEnabled())
+    DEBUG(dbgs() << "Disabled scoreboard hazard recognizer\n");
+  else {
+    // A nonempty itinerary must have a SchedModel.
+    IssueWidth = ItinData->SchedModel->IssueWidth;
+    DEBUG(dbgs() << "Using scoreboard hazard recognizer: Depth = "
+          << ScoreboardDepth << '\n');
+  }
 }
 
 void ScoreboardHazardRecognizer::Reset() {
@@ -151,7 +159,7 @@ ScoreboardHazardRecognizer::getHazardType(SUnit *SU, int Stalls) {
       }
 
       if (!freeUnits) {
-        DEBUG(dbgs() << "*** Hazard in cycle " << (cycle + i) << ", ");
+        DEBUG(dbgs() << "*** Hazard in cycle +" << StageCycle << ", ");
         DEBUG(dbgs() << "SU(" << SU->NodeNum << "): ");
         DEBUG(DAG->dumpNode(SU));
         return Hazard;