[llvm] [ArgPromotion] Handle pointer arguments of recursive calls (PR #78735)

[Vedant Paranjape via llvm-commits]

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@@ -422,13 +422,16 @@ doPromotion(Function *F, FunctionAnalysisManager &FAM,
 
 /// Return true if we can prove that all callees pass in a valid pointer for the
 /// specified function argument.
-static bool allCallersPassValidPointerForArgument(Argument *Arg,
-                                                  Align NeededAlign,
-                                                  uint64_t NeededDerefBytes) {
+static bool allCallersPassValidPointerForArgument(
+    Argument *Arg, SmallPtrSet<CallBase *, 4> &RecursiveCalls,
+    Align NeededAlign, uint64_t NeededDerefBytes) {
   Function *Callee = Arg->getParent();
   const DataLayout &DL = Callee->getParent()->getDataLayout();
   APInt Bytes(64, NeededDerefBytes);
 
+  if (RecursiveCalls.size())
+    return true;
----------------
vedantparanjape-amd wrote:

> Reading the testcase... the argument isn't marked dereferenceable for the definition of foo(), and we don't have any information in bar(), so the current logic can't prove it's dereferenceable.

Yes, that's true. Do, you suggest I add the !dereferenceable metadata to this and run the testcase ?

> It might be possible to prove the argument is dereferenceable because there's a load on all paths through foo(), but that logic shouldn't be in ArgPromotion; it should be in function-attrs, or something like that.

Makes sense

https://github.com/llvm/llvm-project/pull/78735