[5.0.x] Force alignment of opal_atomic_int128_t to be 16B #13282
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Some architectures will align 128bit integer on 8B but require 16B alignment for 128bit CAS instructions and otherwise fall back to a lock-based atomicity model. By forcing 16bit alignment we can ensure that the variables are properly aligned and the fall-back is not triggered. Thanks to Ulrich Weigand for the analysis and proposed fix in open-mpi#10988 (comment). Signed-off-by: Joseph Schuchart <joseph.schuchart@stonybrook.edu> (cherry picked from commit d5c84ea)
bosilca
approved these changes
May 29, 2025
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Some architectures will align 128bit integer on 8B but require 16B alignment for 128bit CAS instructions and otherwise fall back to a lock-based atomicity model. By forcing 16bit alignment we can ensure that the variables are properly aligned and the fall-back is not triggered.
Thanks to Ulrich Weigand for the analysis and proposed fix in #10988 (comment).
Backport of #13281 to v5.0.x
(cherry picked from commit d5c84ea)