mi-sched: Precompute a PressureDiff for each instruction, adjust for liveness later.

Created SUPressureDiffs array to hold the per node PDiff computed during DAG building.

Added a getUpwardPressureDelta API that will soon replace the old
one. Compute PressureDelta here from the precomputed PressureDiffs.

Updating for liveness will come next.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189640 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/ScheduleDAGInstrs.cpp

@@ -690,7 +690,8 @@ void ScheduleDAGInstrs::initSUnits() {
 /// DAG builder is an efficient place to do it because it already visits
 /// operands.
 void ScheduleDAGInstrs::buildSchedGraph(AliasAnalysis *AA,
-                                        RegPressureTracker *RPTracker) {
+                                        RegPressureTracker *RPTracker,
+                                        PressureDiffs *PDiffs) {
   const TargetSubtargetInfo &ST = TM.getSubtarget<TargetSubtargetInfo>();
   bool UseAA = EnableAASchedMI.getNumOccurrences() > 0 ? EnableAASchedMI
                                                        : ST.useAA();
@@ -699,6 +700,9 @@ void ScheduleDAGInstrs::buildSchedGraph(AliasAnalysis *AA,
   // Create an SUnit for each real instruction.
   initSUnits();
 
+  if (PDiffs)
+    PDiffs->init(SUnits.size());
+
   // We build scheduling units by walking a block's instruction list from bottom
   // to top.
 
@@ -746,17 +750,18 @@ void ScheduleDAGInstrs::buildSchedGraph(AliasAnalysis *AA,
       DbgMI = MI;
       continue;
     }
+    SUnit *SU = MISUnitMap[MI];
+    assert(SU && "No SUnit mapped to this MI");
+
     if (RPTracker) {
-      RPTracker->recede();
+      PressureDiff *PDiff = PDiffs ? &(*PDiffs)[SU->NodeNum] : 0;
+      RPTracker->recede(PDiff);
       assert(RPTracker->getPos() == prior(MII) && "RPTracker can't find MI");
     }
 
     assert((CanHandleTerminators || (!MI->isTerminator() && !MI->isLabel())) &&
            "Cannot schedule terminators or labels!");
 
-    SUnit *SU = MISUnitMap[MI];
-    assert(SU && "No SUnit mapped to this MI");
-
     // Add register-based dependencies (data, anti, and output).
     bool HasVRegDef = false;
     for (unsigned j = 0, n = MI->getNumOperands(); j != n; ++j) {