[InstCombine] Fix comments. NFC.

Author: dtcxzyw

llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp

@@ -1868,8 +1868,8 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
   if (Instruction *Res = foldBinOpOfSelectAndCastOfSelectCondition(I))
     return Res;
 
-  // Re-enqueue the induction variable of add recurrence if we infer new
-  // nuw/nsw flags.
+  // Re-enqueue users of the induction variable of add recurrence if we infer
+  // new nuw/nsw flags.
   if (Changed) {
     PHINode *PHI;
     Value *Start, *Step;