[llvm] [DAGCombiner] Don't fold cheap extracts of multiple use splats (PR #134120)

[Simon Pilgrim via llvm-commits]

================
@@ -20223,17 +20223,18 @@ performExtractSubvectorCombine(SDNode *N, TargetLowering::DAGCombinerInfo &DCI,
     return SDValue();
 
   EVT VT = N->getValueType(0);
-  if (!VT.isScalableVector() || VT.getVectorElementType() != MVT::i1)
-    return SDValue();
-
   SDValue V = N->getOperand(0);
 
+  if (VT.isScalableVector() != V->getValueType(0).isScalableVector())
+    return SDValue();
----------------
RKSimon wrote:

Maybe add a explanatory comment to explain this? 

https://github.com/llvm/llvm-project/pull/134120