OSSA lifetime canonicalization can take a very long time in certain
cases in which there are large basic blocks. to mitigate this, add logic
to skip walking the liveness boundary for extending liveness to dead
ends when there aren't any dead ends in the function.
Updates `DeadEndBlocks` with a new `isEmpty` method and cache to
determine if there are any dead-end blocks in a given function.
(cherry picked from commit 1f3f830fc7)
When hoisting destroys of aggregates, an attempt is made to fold the
destroys of individual fields into the foregoing instructions. If the
aggregate is noncopyable, this transformation is illegal.
When hoisting destroys of aggregates, an attempt is made to fold the
destroys of individual fields into the foregoing instructions. If the
aggregate is nonescapable, this transformation is illegal.
rdar://152195094
In case of ObjectiveC classes, the runtime type can differ from its declared type.
Therefore a cast between (compile-time) unrelated classes may succeed at runtime.
rdar://149810124
A trivial store is allowed to occur on an existing live value, and should not
trigger an attempt to destroy the original value completely. Fixes rdar://147791932.
When performing a dynamic cast to an existential type that satisfies
(Metatype)Sendable, it is unsafe to allow isolated conformances of any
kind to satisfy protocol requirements for the existential. Identify
these cases and mark the corresponding cast instructions with a new flag,
`[prohibit_isolated_conformances]` that will be used to indicate to the
runtime that isolated conformances need to be rejected.
* factor out common methods of AST Type/CanonicalType into a `TypeProperties` protocol.
* add more APIs to AST Type/CanoncialType.
* move `MetatypeRepresentation` from SIL.Type to AST.Type and implement it with a swift enum.
* let `Builder.createMetatype` get a CanonicalType as instance type, because the instance type must not be a lowered type.
This transformation is invalid without complete liveness. Add a release assert
to check this. Temporarily hide the assert under -verify-lifetime-completion
until the passes that use this utility are fixed to check escapes.
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.
At one point, OpenedArchetypeType did not exist as a separate subclass
of ArchetypeType, so this method did something. Now, it's just
equivalent to calling is<> or isa<>.
I also removed a couple of asserts that were obvious no-ops as a result.
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 API only makes sense for a scoped borrow-introducer such as:
- reborrow
- owned mark_dependence
Borrowing operands that forward guaranteed values do not have scope-ending uses.
To handle borrowing operands that produce a dependence value but do not create a
nested borrow scope. This includes non-reborrow borrowed-from and guaranteed
mark_dependence [nonescaping].
Only return false if the visitor returns false. Clients were ignoring the
result.
If the BorrowingOperand does not create a borrow scope, call visitUnknownUse
instead.
Until we have complete lifetimes, to avoid breaking code that cannot handle dead
defs, consider a dead borrow scope to be an unknown use.
The check is not perfect, because it only checks that the base operand is alive _at_ the mark_dependence.
Ideally it should check that the base operand is alive during the whole lifetime of the value operand.
If the base value of a mark_dependence is an address, that memory location must be initialized at the mark_dependence.
This requires that the mark_dependence is considered to read from the base address.
This fixes an OSSA verification bug introduced here:
commit 79b649854b
Author: Meghana Gupta <meghanavgupta@gmail.com>
Date: Wed Jan 22 01:24:49 2025
Fix operand ownership of mark_dependence [nonescaping] of address values
The bug only showed up with mark_dependence [nonescaping], which means mainly
affects `~Escapable` types. Adddressors happened to work because SILGen was
emitting a borrow scope around them.
Rather than reverting the change above, this fix migrates mark_dependence
[nonescaping] to an implicit borrow scope.
Fixes rdar://144199759 (Assert: mark_dependence [nonescaping]:
ownership incompatible with an owned value)
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.
The problem with `is_escaping_closure` was that it didn't consume its operand and therefore reference count checks were unreliable.
For example, copy-propagation could break it.
As this instruction was always used together with an immediately following `destroy_value` of the closure, it makes sense to combine both into a `destroy_not_escaped_closure`.
It
1. checks the reference count and returns true if it is 1
2. consumes and destroys the operand
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)
}
The reason why I am doing this is that in certain cases the AST captures indices
will never actually line up with partial apply capture indices since we seem to
"smush" together closures and locally defined functions.
NOTE: The reason for the really small amount of test changes is that this change
does not change the actual output by design. The only cases I had to change were
a case where we began to emit a better diagnostic and also where I added code
coverage around _ and let _ since those require ignored_use to be implemented so
that they would be diagnosed (previously we just did not emit anything so we
couldn't emit the diagnostic at the SIL level).
rdar://142661388
