cpp2w: exclude NORETURN from tecotsb target endpoint#9
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Models the non-returning atomic reduction atomic_store_add_explicit from P3111R0 (Atomic Reduction Operations): https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p3111r0.html A non-returning RMW (tagged NORETURN) should not anchor the tecotsb ordering edge the way a value-returning RMW does. Excluding NORETURN from the target [A] endpoint lets a release store_add not establish message-passing synchronization, so the stale-read outcome {r0=0, y=2} becomes observable. Adds tests/mp/mp-store-add.litmus and mp-fetch-add.litmus: under the patched cpp2w, store_add -> 4 states (incl. {r0=0,y=2}); fetch_add -> 3 states (forbids it). The other models (cpp11, cpp17, rc11, rc17) already support store_add (same 4-state weak behaviour); they have no tecotsb relation, so a non-returning RMW never over-synchronizes there. cpp2w was the sole outlier. herd7 does not support store_add (its CSem is a stub), so no .litmus.expected can be generated; reproduced/validated with dartagnan (Dat3M exploration_mode branch, commit b360545), see hernanponcedeleon/Dat3M#984. Co-authored-by: Hernan Ponce de Leon <hernanl.leon@huawei.com>
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Discussed with Simon and Gonzalo, cpp2w is already too strong, cpp17 correctly models store_add using Dartagnan already. so I will close this PR, add the tests from this PR to PR #8, and use cpp17 for testing |
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Models the non-returning atomic reduction atomic_store_add_explicit from P3111R0 (Atomic Reduction Operations):
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p3111r0.html
A non-returning RMW (tagged NORETURN) should not anchor the tecotsb ordering edge the way a value-returning RMW does. Excluding NORETURN from the target [A] endpoint lets a release store_add not establish message-passing synchronization, so the stale-read outcome {r0=0, y=2} becomes observable.
Adds tests/mp/mp-store-add.litmus and mp-fetch-add.litmus: under the patched cpp2w, store_add -> 4 states (incl. {r0=0,y=2}); fetch_add -> 3 states (forbids it).
The other models (cpp11, cpp17, rc11, rc17) already support store_add (same 4-state weak behaviour); they have no tecotsb relation, so a non-returning RMW never over-synchronizes there. cpp2w was the sole outlier.
herd7 does not support store_add (its CSem is a stub), so no .litmus.expected can be generated; reproduced/validated with dartagnan (Dat3M exploration_mode branch, commit b360545), see
hernanponcedeleon/Dat3M#984.