[NO MERGE] Exclusive key path fix #16016
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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
Add dynamic enforcement of exclusive access when a KeyPath directly accesses a final stored property on an instance of a class. For read-only projections, this begins and ends the access immediately. For mutable projections, this uses the ClassHolder to perform a long-term access that lasts as long as the lifetime of the ClassHolder. rdar://problem/31972680
…ift_dumpTrackedAccesses(). This makes it easy to perform printf debugging in the debugger. I have found it to be useful in understanding programs around exclusivity quickly.
gottesmm
commented
Apr 18, 2018
| writeAndPerform(&c[keyPath: \C.f]) { | ||
| let x = c[keyPath: \C.f] | ||
| _blackHole(x) | ||
| // CHECK-LABEL: Overlapping Key Path Write Access and Key Path Read Access |
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@atrick This is the one that is failing now.
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