Revert "[SLP]Allow masked gathers only if allowed by target."

This reverts commit fd18547. Need to
add a check for the size of the vectorization tree to avoid some extra
vectorization.

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -3921,31 +3921,9 @@ InstructionCost BoUpSLP::getEntryCost(TreeEntry *E) {
                                          CostKind, VL0);
       } else {
         assert(E->State == TreeEntry::ScatterVectorize && "Unknown EntryState");
-        if (TTI->isLegalMaskedGather(VecTy, alignment)) {
-          VecLdCost = TTI->getGatherScatterOpCost(
-              Instruction::Load, VecTy,
-              cast<LoadInst>(VL0)->getPointerOperand(),
-              /*VariableMask=*/false, alignment, CostKind, VL0);
-        } else {
-          // Lower just to a gather if masked gather is not legal. Also,
-          // compensate the cost of next entry for pointers.
-          VecLdCost =
-              getGatherCost(VL);
-          // Tru to compensate the cost of the next entry for pointers iff all
-          // users are ScatterVectorize nodes.
-          const auto *It = find_if(
-              VectorizableTree, [E](const std::unique_ptr<TreeEntry> &TE) {
-                return !TE->UserTreeIndices.empty() &&
-                       all_of(TE->UserTreeIndices,
-                              [](const EdgeInfo &EI) {
-                                return EI.UserTE->State ==
-                                       TreeEntry::ScatterVectorize;
-                              }) &&
-                       TE->UserTreeIndices.front().UserTE == E;
-              });
-          if (It != VectorizableTree.end())
-            VecLdCost -= getEntryCost(It->get());
-        }
+        VecLdCost = TTI->getGatherScatterOpCost(
+            Instruction::Load, VecTy, cast<LoadInst>(VL0)->getPointerOperand(),
+            /*VariableMask=*/false, alignment, CostKind, VL0);
       }
       if (!NeedToShuffleReuses && !E->ReorderIndices.empty()) {
         SmallVector<int> NewMask;