[all-commits] [llvm/llvm-project] 8870ce: [flang][docs] Add note about Cray pointers and the...

[Asher Mancinelli via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 8870ce1aa0ddf4df4f25ae834a1fab167895892d
      https://github.com/llvm/llvm-project/commit/8870ce1aa0ddf4df4f25ae834a1fab167895892d
  Author: Asher Mancinelli <ashermancinelli at gmail.com>
  Date:   2025-05-05 (Mon, 05 May 2025)

  Changed paths:
    M flang/docs/Aliasing.md

  Log Message:
  -----------
  [flang][docs] Add note about Cray pointers and the TARGET attribute (#137993)

We found some tests checking for loops assigning between Cray pointer
handles and their pointees which produced "incorrect" results with
optimizations enabled; this is because the compiler expects Cray
pointers not to alias with any other entity.

[The HPE documentation for Cray Fortran extensions
specifies:](https://support.hpe.com/hpesc/public/docDisplay?docId=a00113911en_us&docLocale=en_US&page=Types.html#cray-poiter-type)

> the compiler assumes that the storage of a pointee is
> never overlaid on the storage of another variable

Jean pointed out that if a user's code uses entities that alias via Cray
pointers, they may add the TARGET attribute to inform Flang of this
aliasing, but that Flang's behavior is in line with Cray's own
documentation and we should not make any changes to our alias analysis
to try and detect this case.

Updating documentation so that users that encounter this situation have
a way to allow their code to compile as they intend.



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