Adjust pre-RA scheduling heuristic

Adjust pre-RA scheduling heuristic

Author: bcheng0127

visa/LocalScheduler/G4_Sched.cpp

@@ -1672,8 +1672,8 @@ bool BB_Scheduler::scheduleBlockForLatency(unsigned &MaxPressure,
       return false;
 
     // UpperBoundGRF == 0 means we are scheduling for the fixed number of GRF
-    if (UpperBoundGRF == 0 &&
-        MaxPressure >= getLatencyHidingThreshold(kernel, nr))
+    unsigned LatencyPressureThreshold = getLatencyHidingThreshold(kernel, nr);
+    if (UpperBoundGRF == 0 && MaxPressure >= LatencyPressureThreshold)
       return false;
 
     // simple ROI check.
@@ -1685,8 +1685,15 @@ bool BB_Scheduler::scheduleBlockForLatency(unsigned &MaxPressure,
           NumOfHighLatencyInsts++;
       }
     }
-
-    return NumOfHighLatencyInsts >= 2;
+    if (kernel.fg.builder->hasFiveALUPipes()) {
+      // For latest platform, do scheduling for kernels with low register
+      // pressure to improve ILP. Currently, half pressure threshold is used.
+      // Maybe tuned in future.
+      return (NumOfHighLatencyInsts >= 2) ||
+             (MaxPressure < (LatencyPressureThreshold / 2));
+    } else {
+      return (NumOfHighLatencyInsts >= 2);
+    }
   };
 
   unsigned NumGrfs =