[LV] Also handle non-uniform scalarized loads when processing AddrDefs.

Loads of addresses are scalarized and have their costs computed w/o
scalarization overhead. Consistently apply this logic also to
non-uniform loads that are already scalarized, to ensure their costs are
consistent with other scalarized lodas that are used as addresses.

(cherry picked from commit 7dd9b3d)

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -5738,8 +5738,11 @@ void LoopVectorizationCostModel::setCostBasedWideningDecision(ElementCount VF) {
       // if the loaded register is involved in an address computation, it is
       // instead changed here when we know this is the case.
       InstWidening Decision = getWideningDecision(I, VF);
-      if (Decision == CM_Widen || Decision == CM_Widen_Reverse)
-        // Scalarize a widened load of address.
+      if (Decision == CM_Widen || Decision == CM_Widen_Reverse ||
+          (!isPredicatedInst(I) && !Legal->isUniformMemOp(*I, VF) &&
+           Decision == CM_Scalarize))
+        // Scalarize a widened load of address or update the cost of a scalar
+        // load of an address.
         setWideningDecision(
             I, VF, CM_Scalarize,
             (VF.getKnownMinValue() *