[llvm] [InstCombine] Re-queue users of phi when nsw/nuw flags of add are inferred (PR #113933)

[Yingwei Zheng via llvm-commits]

================
@@ -1868,6 +1868,13 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
   if (Instruction *Res = foldBinOpOfSelectAndCastOfSelectCondition(I))
     return Res;
 
+  if (Changed) {
+    for (User *U : I.users()) {
+      if (auto *PHI = dyn_cast<PHINode>(U))
+        Worklist.pushUsersToWorkList(*PHI);
+    }
+  }
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dtcxzyw wrote:

> I don't quite understand why this isn't already handled by pushUsersToWorkList in the normal InstCombine loop

Take the above case as an example. If the add instruction is updated, `%iv` and `%phi` will be re-queued. But `%cmp` cannot be re-queued since we do not change `%iv`.


https://github.com/llvm/llvm-project/pull/113933