BBVectorize: Account for internal shuffle costs

When target costs are available, use them to account for the costs of
shuffles on internal edges of the DAG of candidate pairs.

Because the shuffle costs here are currently for only the internal edges,
the current target cost model is trivial, and the chain depth requirement
is still in place, I don't yet have an easy test
case. Nevertheless, by looking at the debug output, it does seem to do the right
think to the effective "size" of each DAG of candidate pairs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167217 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Vectorize/BBVectorize.cpp b/lib/Transforms/Vectorize/BBVectorize.cpp
index 40277dc..6e36ff7 100644 (file)
--- a/lib/Transforms/Vectorize/BBVectorize.cpp
+++ b/lib/Transforms/Vectorize/BBVectorize.cpp
@@ -246,7 +246,10 @@ namespace {
     void choosePairs(std::multimap<Value *, Value *> &CandidatePairs,
                         DenseMap<ValuePair, int> &CandidatePairCostSavings,
                         std::vector<Value *> &PairableInsts,
+                        DenseSet<ValuePair> &FixedOrderPairs,
+                        DenseMap<VPPair, unsigned> &PairConnectionTypes,
                         std::multimap<ValuePair, ValuePair> &ConnectedPairs,
+                        std::multimap<ValuePair, ValuePair> &ConnectedPairDeps,
                         DenseSet<ValuePair> &PairableInstUsers,
                         DenseMap<Value *, Value *>& ChosenPairs);
 
@@ -308,7 +311,10 @@ namespace {
                       std::multimap<Value *, Value *> &CandidatePairs,
                       DenseMap<ValuePair, int> &CandidatePairCostSavings,
                       std::vector<Value *> &PairableInsts,
+                      DenseSet<ValuePair> &FixedOrderPairs,
+                      DenseMap<VPPair, unsigned> &PairConnectionTypes,
                       std::multimap<ValuePair, ValuePair> &ConnectedPairs,
+                      std::multimap<ValuePair, ValuePair> &ConnectedPairDeps,
                       DenseSet<ValuePair> &PairableInstUsers,
                       std::multimap<ValuePair, ValuePair> &PairableInstUserMap,
                       DenseMap<Value *, Value *> &ChosenPairs,
@@ -550,6 +556,7 @@ namespace {
       case Instruction::Trunc:
       case Instruction::FPTrunc:
       case Instruction::BitCast:
+      case Instruction::ShuffleVector:
         return VTTI->getCastInstrCost(Opcode, T1, T2);
       }
 
@@ -714,7 +721,8 @@ namespace {
 
       DenseMap<Value *, Value *> ChosenPairs;
       choosePairs(CandidatePairs, CandidatePairCostSavings,
-        PairableInsts, ConnectedPairs,
+        PairableInsts, FixedOrderPairs, PairConnectionTypes,
+        ConnectedPairs, ConnectedPairDeps,
         PairableInstUsers, ChosenPairs);
 
       if (ChosenPairs.empty()) continue;
@@ -1597,7 +1605,10 @@ namespace {
                       std::multimap<Value *, Value *> &CandidatePairs,
                       DenseMap<ValuePair, int> &CandidatePairCostSavings,
                       std::vector<Value *> &PairableInsts,
+                      DenseSet<ValuePair> &FixedOrderPairs,
+                      DenseMap<VPPair, unsigned> &PairConnectionTypes,
                       std::multimap<ValuePair, ValuePair> &ConnectedPairs,
+                      std::multimap<ValuePair, ValuePair> &ConnectedPairDeps,
                       DenseSet<ValuePair> &PairableInstUsers,
                       std::multimap<ValuePair, ValuePair> &PairableInstUserMap,
                       DenseMap<Value *, Value *> &ChosenPairs,
@@ -1654,10 +1665,53 @@ namespace {
 
       int EffSize = 0;
       if (VTTI) {
+        // The node weights represent the cost savings associated with
+        // fusing the pair of instructions.
         for (DenseSet<ValuePair>::iterator S = PrunedTree.begin(),
              E = PrunedTree.end(); S != E; ++S) {
           if (getDepthFactor(S->first))
             EffSize += CandidatePairCostSavings.find(*S)->second;
+
+        // The edge weights contribute in a negative sense: they represent
+        // the cost of shuffles.
+          VPPIteratorPair IP = ConnectedPairDeps.equal_range(*S);
+          if (IP.first != ConnectedPairDeps.end()) {
+            unsigned NumDepsDirect = 0, NumDepsSwap = 0;
+            for (std::multimap<ValuePair, ValuePair>::iterator Q = IP.first;
+                 Q != IP.second; ++Q) {
+              DenseMap<VPPair, unsigned>::iterator R =
+                PairConnectionTypes.find(VPPair(Q->second, Q->first));
+              assert(R != PairConnectionTypes.end() &&
+                     "Cannot find pair connection type");
+              if (R->second == PairConnectionDirect)
+                ++NumDepsDirect;
+              else if (R->second == PairConnectionSwap)
+                ++NumDepsSwap;
+            }
+
+            // If there are more swaps than direct connections, then
+            // the pair order will be flipped during fusion. So the real
+            // number of swaps is the minimum number.
+            bool FlipOrder = !FixedOrderPairs.count(*S) &&
+              ((NumDepsSwap > NumDepsDirect) ||
+                FixedOrderPairs.count(ValuePair(S->second, S->first)));
+
+            for (std::multimap<ValuePair, ValuePair>::iterator Q = IP.first;
+                 Q != IP.second; ++Q) {
+              DenseMap<VPPair, unsigned>::iterator R =
+                PairConnectionTypes.find(VPPair(Q->second, Q->first));
+              assert(R != PairConnectionTypes.end() &&
+                     "Cannot find pair connection type");
+              Type *Ty1 = Q->second.first->getType(),
+                   *Ty2 = Q->second.second->getType();
+              Type *VTy = getVecTypeForPair(Ty1, Ty2);
+              if ((R->second == PairConnectionDirect && FlipOrder) ||
+                  (R->second == PairConnectionSwap && !FlipOrder)  ||
+                  R->second == PairConnectionSplat)
+                EffSize -= (int) getInstrCost(Instruction::ShuffleVector,
+                                              VTy, VTy);
+            }
+          }
         }
       } else {
         for (DenseSet<ValuePair>::iterator S = PrunedTree.begin(),
@@ -1685,7 +1739,10 @@ namespace {
                       std::multimap<Value *, Value *> &CandidatePairs,
                       DenseMap<ValuePair, int> &CandidatePairCostSavings,
                       std::vector<Value *> &PairableInsts,
+                      DenseSet<ValuePair> &FixedOrderPairs,
+                      DenseMap<VPPair, unsigned> &PairConnectionTypes,
                       std::multimap<ValuePair, ValuePair> &ConnectedPairs,
+                      std::multimap<ValuePair, ValuePair> &ConnectedPairDeps,
                       DenseSet<ValuePair> &PairableInstUsers,
                       DenseMap<Value *, Value *>& ChosenPairs) {
     bool UseCycleCheck =
@@ -1704,7 +1761,8 @@ namespace {
       int BestEffSize = 0;
       DenseSet<ValuePair> BestTree;
       findBestTreeFor(CandidatePairs, CandidatePairCostSavings,
-                      PairableInsts, ConnectedPairs,
+                      PairableInsts, FixedOrderPairs, PairConnectionTypes,
+                      ConnectedPairs, ConnectedPairDeps,
                       PairableInstUsers, PairableInstUserMap, ChosenPairs,
                       BestTree, BestMaxDepth, BestEffSize, ChoiceRange,
                       UseCycleCheck);