[clang] [llvm] [Arch64][SVE] Lower svrev_* to llvm.vector.reverse and fold svrev(svrev(x)) -> x (PR #116422)

[Benjamin Maxwell via llvm-commits]

================
@@ -21962,6 +21962,35 @@ SDValue tryLowerPartialReductionToWideAdd(SDNode *N,
   return DAG.getNode(TopOpcode, DL, AccVT, BottomNode, ExtOp);
 }
 
+static SDValue foldRevInvolution(SDNode *N) {
+  SDValue InnerRev = N->getOperand(1);
+  if (!InnerRev.hasOneUse())
+    return SDValue();
----------------
MacDue wrote:

Does it matter if the inner rev has more than one use? This only replaces the outer rev, so if there's another use of the inner rev it should be preserved. 

https://github.com/llvm/llvm-project/pull/116422