[llvm] [SimplifyCFG] Switch to use `paramHasNonNullAttr` (PR #125383)

[Nikita Popov via llvm-commits]

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@@ -8276,15 +8276,17 @@ static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I, bool PtrValu
         return true;
 
       if (C->isNullValue()) {
-        for (const llvm::Use &Arg : CB->args())
-          if (Arg == I) {
-            unsigned ArgIdx = CB->getArgOperandNo(&Arg);
-            if (CB->isPassingUndefUB(ArgIdx) &&
-                CB->paramHasAttr(ArgIdx, Attribute::NonNull)) {
-              // Passing null to a nonnnull+noundef argument is undefined.
-              return !PtrValueMayBeModified;
+        if (C->getType()->isPointerTy()) {
+          for (const llvm::Use &Arg : CB->args())
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nikic wrote:

We should switch this code to work on `Use` instead of `User` so we can directly get the right argument...

https://github.com/llvm/llvm-project/pull/125383