[llvm] [clang] [clang-tools-extra] [SLP]Improve findReusedOrderedScalars and graph rotation. (PR #77529)

[Simon Pilgrim via llvm-commits]

================
@@ -858,7 +858,7 @@ static void addMask(SmallVectorImpl<int> &Mask, ArrayRef<int> SubMask,
 /// values 3 and 7 respectively:
 /// before:  6 9 5 4 9 2 1 0
 /// after:   6 3 5 4 7 2 1 0
-static void fixupOrderingIndices(SmallVectorImpl<unsigned> &Order) {
+static void fixupOrderingIndices(MutableArrayRef<unsigned> Order) {
----------------
RKSimon wrote:

Pull out this NFC change

https://github.com/llvm/llvm-project/pull/77529