[LV] fix thinko

Author: artagnon

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -4871,10 +4871,10 @@ bool LoopVectorizationPlanner::isMoreProfitable(
   // Assume vscale may be larger than 1 (or the value being tuned for),
   // so that scalable vectorization is slightly favorable over fixed-width
   // vectorization.
-  bool AXorBScalable = A.Width.isScalable() ^ B.Width.isScalable();
-  auto CmpFn = [AXorBScalable](const InstructionCost &LHS,
-                               const InstructionCost &RHS) {
-    return AXorBScalable ? LHS <= RHS : LHS < RHS;
+  bool PreferScalable = A.Width.isScalable() && !B.Width.isScalable();
+  auto CmpFn = [PreferScalable](const InstructionCost &LHS,
+                                const InstructionCost &RHS) {
+    return PreferScalable ? LHS <= RHS : LHS < RHS;
   };
 
   // To avoid the need for FP division: