[SLP][NFC]Use MutableArrayRef instead of SmallVectorImpl&, rename

function, NFC.

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -553,8 +553,8 @@ static std::optional<unsigned> getExtractIndex(Instruction *E) {
 /// successful, the matched scalars are replaced by poison values in \p VL for
 /// future analysis.
 static std::optional<TTI::ShuffleKind>
-tryToGatherExtractElements(SmallVectorImpl<Value *> &VL,
-                           SmallVectorImpl<int> &Mask) {
+tryToGatherSingleRegisterExtractElements(MutableArrayRef<Value *> VL,
+                                         SmallVectorImpl<int> &Mask) {
   // Scan list of gathered scalars for extractelements that can be represented
   // as shuffles.
   MapVector<Value *, SmallVector<int>> VectorOpToIdx;
@@ -641,7 +641,7 @@ tryToGatherExtractElements(SmallVectorImpl<Value *> &VL,
   if (!Res) {
     // TODO: try to check other subsets if possible.
     // Restore the original VL if attempt was not successful.
-    VL.swap(SavedVL);
+    copy(SavedVL, VL.begin());
     return std::nullopt;
   }
   // Restore unused scalars from mask, if some of the extractelements were not
@@ -7616,7 +7616,7 @@ BoUpSLP::getEntryCost(const TreeEntry *E, ArrayRef<Value *> VectorizedVals,
     std::optional<TargetTransformInfo::ShuffleKind> GatherShuffle;
     SmallVector<const TreeEntry *> Entries;
     // Check for gathered extracts.
-    ExtractShuffle = tryToGatherExtractElements(GatheredScalars, ExtractMask);
+    ExtractShuffle = tryToGatherSingleRegisterExtractElements(GatheredScalars, ExtractMask);
     SmallVector<Value *> IgnoredVals;
     if (UserIgnoreList)
       IgnoredVals.assign(UserIgnoreList->begin(), UserIgnoreList->end());
@@ -10166,7 +10166,8 @@ ResTy BoUpSLP::processBuildVector(const TreeEntry *E, Args &...Params) {
   Type *ScalarTy = GatheredScalars.front()->getType();
   if (!all_of(GatheredScalars, UndefValue::classof)) {
     // Check for gathered extracts.
-    ExtractShuffle = tryToGatherExtractElements(GatheredScalars, ExtractMask);
+    ExtractShuffle =
+        tryToGatherSingleRegisterExtractElements(GatheredScalars, ExtractMask);
     SmallVector<Value *> IgnoredVals;
     if (UserIgnoreList)
       IgnoredVals.assign(UserIgnoreList->begin(), UserIgnoreList->end());