Functional changes:
Improved modeling of dependence on local variable scopes.
For nested modify->read accesses, only extend the read accesses.
Avoid making a read access dependent on an inout argument.
The following needs to be an error to prevent span storage from being modified:
@lifetime(owner)
foo(owner: inout Owner) -> Span {
owner.span
}
Improve usability of borrowing trivial values (UnsafePointer). Allow:
let span = Span(buffer.baseAddress)
Ignore access scopes for trivial values.
Structural changes:
Delete the LifetimeDependenceUseDefWalker.
Encapsulate all logic for variable introducers within the LifetimeDependenceInsertion pass. Once mark_dependence instructions are inserted, no subsequent pass needs to think about the "root" of a dependence.
Fixes: rdar://142451725 (Escape analysis fails with mutations)
This encourages AccessPathWalker clients to handle enclosing mark_deps. In
some cases, it is necessary. The accessBaseWithScopes API now provides both
nested begin_access and mark_dependence.
This pass rewrites mark_depenendence to ignore "useless" borrow scopes. It was
also accidentally rewriting a dependence on a loaded value, which may redirect the
dependence to the access scope used to load that value. That access scope may be
narrower than the lifetime of the loaded value which could result in invalid
SIL. Do not rewrite this mark_dependence:
%access = begin_access [read] [unknown] %base
%load = load [trivial] %access
end_access %access
%adr = pointer_to_address
%md = mark_dependence [unresolved] %adr on %load
Fixes rdar://142424000 (Swift compiler crashes with Assertion failed
(isa<UnreachableInst>(block->getTerminator())))
Handle all combinations of nested dependence scopes: access scopes, coroutines,
and borrow scopes.
This is required to enforce ~Escapable _read accessors and unsafeAddress addressors.
Fixes rdar://140424699 (Invalid SIL is generated by some passes for certain
@lifetime annotations)
by -enable-experimental-feature NonescapableTypes
on the Windows platform
These passes do nothing unless the above feature flag is enabled, so
the only reason to run the pass is to exercise SwiftCompilerSources
and catch invalid SIL.
These passes rely on fundamental SwiftCompilerSources abstractions
which have not yet been tested outside of the passes. They don't yet
handle all SIL patterns, and SIL continues to evolve. We would like to
can these issues quickly as we hit them, but only if we have a way of
reproducing the failure. Currently, we don't have a way of reproducing
Windows-arm64 failures.
Workaround for:
rdar://128434000 ([nonescapable] [LifetimeDependenceInsertion]
Package resolution fails with arm64 Windows toolchain)
Only rewrite the mark_dependence to depend on the function argument when the
dependent value is actually returned.
Also, find all uses even if an escaping use is seen.
