[InstCombine] Fix worklist management in foldXorOfICmps()

Because this code does not use the IC-aware replaceInstUsesWith()
helper, we need to manually push users to the worklist.

This is NFC-ish, in that it may only change worklist order.

Author: nikic

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -2889,6 +2889,7 @@ Value *InstCombiner::foldXorOfICmps(ICmpInst *LHS, ICmpInst *RHS,
           Builder.SetInsertPoint(Y->getParent(), ++(Y->getIterator()));
           Value *NotY = Builder.CreateNot(Y, Y->getName() + ".not");
           // Replace all uses of Y (excluding the one in NotY!) with NotY.
+          Worklist.pushUsersToWorkList(*Y);
           Y->replaceUsesWithIf(NotY,
                                [NotY](Use &U) { return U.getUser() != NotY; });
         }

llvm/test/Transforms/InstCombine/xor-of-icmps-with-extra-uses.ll

@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -instcombine -S | FileCheck %s
+; RUN: opt < %s -instcombine -instcombine-infinite-loop-threshold=2 -S | FileCheck %s
 
 ; These xor-of-icmps could be replaced with and-of-icmps, but %cond0 has extra
 ; uses, so we don't consider it, even though some cases are freely invertible.