Rig TransitiveAddressWalker to keep track of enough information for passes to
correctly check for pointer escapes and dependence uses. Requires for precise
bail-outs and asserts.
Add liveness support for dependent values: borrowed-from & mark_dependence so
they aren't reported as unknown uses.
Centralize the logic in BorrowingOperand::getScopeIntroducingUserResult
and BorrowingOperand::getDependentUserResult().
The extra complexity for traversing phis is not needed now that it handles
borrowed-from instructions. Remove the redundant logic because it complicates
the liveness algorithm and generates confusing results.
This is necessary to fix a recent OSSA bug that breaks common occurrences on
mark_dependence [nonescaping]. Rather than reverting that change above, we make
forward progress toward implicit borrows scopes, as was the original intention.
In the near future, all InteriorPointer instructions will create an implicit
borrow scope. This means we have the option of not emitting extraneous
begin/end_borrow instructions around intructions like ref_element_addr,
open_existential, and project_box. After that, we can also migrate
GuaranteedForwarding instructions like tuple_extract and struct_extract.
Improves OSSALifetimeCompletion to handle trivial variables when running from
SILGenCleanup. This only affects lifetime dependence diagnostics.
For the purpose of lifetime diagnostics, trivial local variables are only valid
within their lexical scope. Sadly, SILGen only know how to insert cleanup code
on normal function exits. SILGenCleanup relies on lifetime completion to fix
lifetimes on dead end paths.
%var = move_value [var_decl]
try_apply %f() : $..., normal bb1, error error
error:
extend_lifetime %var <=== insert this
unreachable
This allows Span to depend on local unsafe pointers AND be used within
throwing closures:
_ = a.withUnsafeBufferPointer {
let buffer = $0
let view = Span(_unsafeElements: buffer)
return view.withUnsafeBufferPointer(\.count)
}
When visiting consumes, also visit `extend_lifetime` instructions.
These instructions are not lifetime ending, but together with the
consumes, they enclose the users of a value.
Add a flag to LinearLiveness to control whether these instructions are
added so that the verifier can use verify that all such instructions
appear outside the linear lifetime boundary (not including them).
"reborrow" flag on the SILArgument avoids transitive walk over the phi operandsi
to determine if it is a reborrow in multiple utilities.
SIL transforms must keep the flag up-to-date by calling SILArgument::setReborrow.
SILVerifier checks to ensure the flag is not invalidated.
Currently "escaping" is not used anywhere.
Since partial_apply [on_stack] is considered as a BorrowingOperand now,
and BorrowingOperand::visitScopeEndingUses can be called on the its forwarded values
lifetime ends, update the assertion to reflect this.
Encapsulate all the complexity of reborrows and guaranteed phi in 3
ownership liveness interfaces:
LinerLiveness, InteriorLiveness, and ExtendedLiveness.
