Remove floats from live range splitting costs.

These floats all represented block frequencies anyway, so just use the
BlockFrequency class directly.

Some floating point computations remain in tryLocalSplit(). They are
estimating spill weights which are still floats.

llvm-svn: 186435

llvm/lib/CodeGen/RegAllocGreedy.cpp

@@ -251,11 +251,11 @@ private:
   void LRE_WillShrinkVirtReg(unsigned);
   void LRE_DidCloneVirtReg(unsigned, unsigned);
 
-  float calcSpillCost();
+  BlockFrequency calcSpillCost();
-  bool addSplitConstraints(InterferenceCache::Cursor, float&);
+  bool addSplitConstraints(InterferenceCache::Cursor, BlockFrequency&);
   void addThroughConstraints(InterferenceCache::Cursor, ArrayRef<unsigned>);
   void growRegion(GlobalSplitCandidate &Cand);
-  float calcGlobalSplitCost(GlobalSplitCandidate&);
+  BlockFrequency calcGlobalSplitCost(GlobalSplitCandidate&);
   bool calcCompactRegion(GlobalSplitCandidate&);
   void splitAroundRegion(LiveRangeEdit&, ArrayRef<unsigned>);
   void calcGapWeights(unsigned, SmallVectorImpl<float>&);
@@ -703,12 +703,12 @@ unsigned RAGreedy::tryEvict(LiveInterval &VirtReg,
 /// that all preferences in SplitConstraints are met.
 /// Return false if there are no bundles with positive bias.
 bool RAGreedy::addSplitConstraints(InterferenceCache::Cursor Intf,
-                                   float &Cost) {
+                                   BlockFrequency &Cost) {
   ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
 
   // Reset interference dependent info.
   SplitConstraints.resize(UseBlocks.size());
-  float StaticCost = 0;
+  BlockFrequency StaticCost = 0;
   for (unsigned i = 0; i != UseBlocks.size(); ++i) {
     const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
     SpillPlacement::BlockConstraint &BC = SplitConstraints[i];
@@ -746,8 +746,8 @@ bool RAGreedy::addSplitConstraints(InterferenceCache::Cursor Intf,
     }
 
     // Accumulate the total frequency of inserted spill code.
-    if (Ins)
+    while (Ins--)
-      StaticCost += Ins * SpillPlacer->getBlockFrequency(BC.Number);
+      StaticCost += SpillPlacer->getBlockFrequency(BC.Number);
   }
   Cost = StaticCost;
 
@@ -880,7 +880,7 @@ bool RAGreedy::calcCompactRegion(GlobalSplitCandidate &Cand) {
   SpillPlacer->prepare(Cand.LiveBundles);
 
   // The static split cost will be zero since Cand.Intf reports no interference.
-  float Cost;
+  BlockFrequency Cost;
   if (!addSplitConstraints(Cand.Intf, Cost)) {
     DEBUG(dbgs() << ", none.\n");
     return false;
@@ -905,8 +905,8 @@ bool RAGreedy::calcCompactRegion(GlobalSplitCandidate &Cand) {
 
 /// calcSpillCost - Compute how expensive it would be to split the live range in
 /// SA around all use blocks instead of forming bundle regions.
-float RAGreedy::calcSpillCost() {
+BlockFrequency RAGreedy::calcSpillCost() {
-  float Cost = 0;
+  BlockFrequency Cost = 0;
   ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
   for (unsigned i = 0; i != UseBlocks.size(); ++i) {
     const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
@@ -925,8 +925,8 @@ float RAGreedy::calcSpillCost() {
 /// pattern in LiveBundles. This cost should be added to the local cost of the
 /// interference pattern in SplitConstraints.
 ///
-float RAGreedy::calcGlobalSplitCost(GlobalSplitCandidate &Cand) {
+BlockFrequency RAGreedy::calcGlobalSplitCost(GlobalSplitCandidate &Cand) {
-  float GlobalCost = 0;
+  BlockFrequency GlobalCost = 0;
   const BitVector &LiveBundles = Cand.LiveBundles;
   ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
   for (unsigned i = 0; i != UseBlocks.size(); ++i) {
@@ -940,8 +940,8 @@ float RAGreedy::calcGlobalSplitCost(GlobalSplitCandidate &Cand) {
       Ins += RegIn != (BC.Entry == SpillPlacement::PrefReg);
     if (BI.LiveOut)
       Ins += RegOut != (BC.Exit == SpillPlacement::PrefReg);
-    if (Ins)
+    while (Ins--)
-      GlobalCost += Ins * SpillPlacer->getBlockFrequency(BC.Number);
+      GlobalCost += SpillPlacer->getBlockFrequency(BC.Number);
   }
 
   for (unsigned i = 0, e = Cand.ActiveBlocks.size(); i != e; ++i) {
@@ -953,8 +953,10 @@ float RAGreedy::calcGlobalSplitCost(GlobalSplitCandidate &Cand) {
     if (RegIn && RegOut) {
       // We need double spill code if this block has interference.
       Cand.Intf.moveToBlock(Number);
-      if (Cand.Intf.hasInterference())
+      if (Cand.Intf.hasInterference()) {
-        GlobalCost += 2*SpillPlacer->getBlockFrequency(Number);
+        GlobalCost += SpillPlacer->getBlockFrequency(Number);
+        GlobalCost += SpillPlacer->getBlockFrequency(Number);
+      }
       continue;
     }
     // live-in / stack-out or stack-in live-out.
@@ -1119,7 +1121,7 @@ unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
                                   SmallVectorImpl<LiveInterval*> &NewVRegs) {
   unsigned NumCands = 0;
   unsigned BestCand = NoCand;
-  float BestCost;
+  BlockFrequency BestCost;
   SmallVector<unsigned, 8> UsedCands;
 
   // Check if we can split this live range around a compact region.
@@ -1127,11 +1129,11 @@ unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
   if (HasCompact) {
     // Yes, keep GlobalCand[0] as the compact region candidate.
     NumCands = 1;
-    BestCost = HUGE_VALF;
+    BestCost = BlockFrequency::getMaxFrequency();
   } else {
     // No benefit from the compact region, our fallback will be per-block
     // splitting. Make sure we find a solution that is cheaper than spilling.
-    BestCost = Hysteresis * calcSpillCost();
+    BestCost = calcSpillCost();
     DEBUG(dbgs() << "Cost of isolating all blocks = " << BestCost << '\n');
   }
 
@@ -1161,7 +1163,7 @@ unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
     Cand.reset(IntfCache, PhysReg);
 
     SpillPlacer->prepare(Cand.LiveBundles);
-    float Cost;
+    BlockFrequency Cost;
     if (!addSplitConstraints(Cand.Intf, Cost)) {
       DEBUG(dbgs() << PrintReg(PhysReg, TRI) << "\tno positive bundles\n");
       continue;
@@ -1197,7 +1199,7 @@ unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
     });
     if (Cost < BestCost) {
       BestCand = NumCands;
-      BestCost = Hysteresis * Cost; // Prevent rounding effects.
+      BestCost = Cost;
     }
     ++NumCands;
   }
@@ -1515,7 +1517,9 @@ unsigned RAGreedy::tryLocalSplit(LiveInterval &VirtReg, AllocationOrder &Order,
   unsigned BestAfter = 0;
   float BestDiff = 0;
 
-  const float blockFreq = SpillPlacer->getBlockFrequency(BI.MBB->getNumber());
+  const float blockFreq =
+    SpillPlacer->getBlockFrequency(BI.MBB->getNumber()).getFrequency() *
+    (1.0f / BlockFrequency::getEntryFrequency());
   SmallVector<float, 8> GapWeight;
 
   Order.rewind();

llvm/lib/CodeGen/SpillPlacement.h

@@ -140,10 +140,8 @@ public:
 
   /// getBlockFrequency - Return the estimated block execution frequency per
   /// function invocation.
-  float getBlockFrequency(unsigned Number) const {
+  BlockFrequency getBlockFrequency(unsigned Number) const {
-    // FIXME: Return the BlockFrequency directly.
+    return BlockFrequencies[Number];
-    const float Scale = 1.0f / BlockFrequency::getEntryFrequency();
-    return BlockFrequencies[Number].getFrequency() * Scale;
   }
 
 private: