[PATCH] D63067: [Attributor] NoAlias on return values.

[Johannes Doerfert via Phabricator via llvm-commits]

jdoerfert added inline comments.


================
Comment at: llvm/include/llvm/Transforms/IPO/Attributor.h:657
+
+  /// Return true if we know that underlying value does not alias.
+  virtual bool isKnownNoAlias() const = 0;
----------------
"does not alias." is confusing, maybe phrase it `is "noalias"`.


================
Comment at: llvm/lib/Transforms/IPO/Attributor.cpp:364
+  return true;
+}
+
----------------
Use the `AAReturnedValuesImpl` instead of an explicit traversal. The `AAReturnedValuesImpl` knows what is returned and through which return instructions. 


================
Comment at: llvm/lib/Transforms/IPO/Attributor.cpp:371
+  if (F.returnDoesNotAlias())
+    return ChangeStatus::UNCHANGED;
+
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Move this check in the `initialize` method.


================
Comment at: llvm/lib/Transforms/IPO/Attributor.cpp:380
+  if (!F.hasExactDefinition() || !F.getReturnType()->isPointerTy() ||
+      !isFunctionMallocLike(F)) {
+    indicatePessimisticFixpoint();
----------------
This is not what we want to check. Look at the returned values and the locations where they are returned.


Repository:
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  https://reviews.llvm.org/D63067/new/

https://reviews.llvm.org/D63067