[Exclusivity] Add support for semantics tag "optimize.sil.preserve_ex… #16004
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…clusivity". This is a special @_semantics attribute that preserves exclusivity even if we are eliminating exclusivity in other parts of a module in release mode. This is done by: 1. Teaching the Access Marker Elimination pass to skip any function with the semantics tag. 2. Requiring all functions with the semantics tag to be noinline. This ensures that the SIL level inliner will not inline these functions into any callers without the protection of the semantics tag. This is enforced in IRGenPrepare and ensures that our access markers will live to IRGen time. 3. In IRGenPrepare, we convert these functions from noinline to always inline. After IRGen this then allows for the LLVM inliner to inline these trivial functions that just perform the exclusivity checks ensuring that we do not have extra calls in the fast path. This ensures that we can fix the keypaths exclusivity issue without having to enable exclusivity across the entire stdlib and deal with any of the potential performance issues therein. rdar://39335800
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@swift-ci smoke test |
atrick
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Apr 18, 2018
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Fantastic. Rigorous checks and tests. 🎖
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@swift-ci smoke test. |
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See #16051 |
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…clusivity".
This is a special @_semantics attribute that preserves exclusivity even if we
are eliminating exclusivity in other parts of a module in release mode. This is
done by:
Teaching the Access Marker Elimination pass to skip any function with the
semantics tag.
Requiring all functions with the semantics tag to be noinline. This ensures
that the SIL level inliner will not inline these functions into any callers
without the protection of the semantics tag. This is enforced in IRGenPrepare
and ensures that our access markers will live to IRGen time.
In IRGenPrepare, we convert these functions from noinline to always
inline. After IRGen this then allows for the LLVM inliner to inline these
trivial functions that just perform the exclusivity checks ensuring that we do
not have extra calls in the fast path.
This ensures that we can fix the keypaths exclusivity issue without having to
enable exclusivity across the entire stdlib and deal with any of the potential
performance issues therein.
rdar://39335800