tree 1193368e335f611a553c3488c75ecd37d8024495
parent 03cc50fd7db734b62783b26e6c6fcfb4f7e33be0
author Tom Eccles <tom.eccles@arm.com> 1747923842 +0100
committer GitHub <noreply@github.com> 1747923842 +0100
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[mlir][OpenMP] add attribute for privatization barrier (#140089)

A barrier is needed at the end of initialization/copying of private
variables if any of those variables is lastprivate. This ensures that
all firstprivate variables receive the original value of the variable
before the lastprivate clause overwrites it.

Previously this barrier was added by the flang fontend, but there is not
a reliable way to put the barrier in the correct place for delayed
privatization, and the OpenMP dialect could some day have other users.
It is important that there are safe ways to use the constructs available
in the dialect.

lastprivate is currently not modelled in the OpenMP dialect, and so
there is no way to reliably determine whether there were lastprivate
variables. Therefore the frontend will have to provide this information
through this new attribute.

Part of a series of patches to fix
https://github.com/llvm/llvm-project/issues/136357