[PATCH] D32006: Mark invariant.group.barrier as inaccessiblememonly

[Piotr Padlewski via Phabricator via llvm-commits]

Prazek added a comment.

In https://reviews.llvm.org/D32006#736448, @sanjoy wrote:

> Doesn't this conflict with the test case you had for https://reviews.llvm.org/D31531:
>
>   void foo() {
>       Base *x = new Base{};
>       new (x) Derived1{};
>       int a = std::launder(x)->foo();
>       new (x) Derived2{};
>       int b = std::launder(x)->foo();
>   }
>
>
> Won't it now be OK to CSE the two `launders` since the only memory changed between the two is visible to the module (and thus not read by an `inaccessiblememonly readonly` function)?


I have to double check that. If this is the case then probably we can remove readonly from the barrier. This way we won't be able to CSE barrier together, but we will be able to DSE through the barrier.


Repository:
  rL LLVM

https://reviews.llvm.org/D32006