[llvm] [SLP] Simplify buildTree() and callees (NFC) (PR #135766)

[Gaëtan Bossu via llvm-commits]

================
@@ -9556,55 +9590,67 @@ static bool tryToFindDuplicates(SmallVectorImpl<Value *> &VL,
     if (Res.second)
       UniqueValues.emplace_back(V);
   }
+
+  // Easy case: VL has unique values and a "natural" size
   size_t NumUniqueScalarValues = UniqueValues.size();
   bool IsFullVectors = hasFullVectorsOrPowerOf2(
       TTI, getValueType(UniqueValues.front()), NumUniqueScalarValues);
   if (NumUniqueScalarValues == VL.size() &&
       (VectorizeNonPowerOf2 || IsFullVectors)) {
     ReuseShuffleIndices.clear();
-  } else {
-    // FIXME: Reshuffing scalars is not supported yet for non-power-of-2 ops.
-    if ((UserTreeIdx.UserTE &&
-         UserTreeIdx.UserTE->hasNonWholeRegisterOrNonPowerOf2Vec(TTI)) ||
-        !hasFullVectorsOrPowerOf2(TTI, getValueType(VL.front()), VL.size())) {
-      LLVM_DEBUG(dbgs() << "SLP: Reshuffling scalars not yet supported "
-                           "for nodes with padding.\n");
-      return false;
-    }
-    LLVM_DEBUG(dbgs() << "SLP: Shuffle for reused scalars.\n");
-    if (NumUniqueScalarValues <= 1 || !IsFullVectors ||
-        (UniquePositions.size() == 1 && all_of(UniqueValues, [](Value *V) {
-           return isa<UndefValue>(V) || !isConstant(V);
-         }))) {
-      if (DoNotFail && UniquePositions.size() > 1 &&
-          NumUniqueScalarValues > 1 && S.getMainOp()->isSafeToRemove() &&
-          all_of(UniqueValues, IsaPred<Instruction, PoisonValue>)) {
-        // Find the number of elements, which forms full vectors.
-        unsigned PWSz = getFullVectorNumberOfElements(
-            TTI, UniqueValues.front()->getType(), UniqueValues.size());
-        PWSz = std::min<unsigned>(PWSz, VL.size());
-        if (PWSz == VL.size()) {
+    return true;
----------------
gbossu wrote:

Fine to me! I'll move the last two commits in a separate patch, and leave the first three ones here then :) They all deal with `tryToFindDuplicates()`, so I guess it does make sense to keep them together still. And it will be a pretty small patch.


https://github.com/llvm/llvm-project/pull/135766