Rewrite the SILCLoners used in SimplifyCFG. For convenience, there is
now simply a BasicBlockCloner and a SILFunctionCloner. It's pretty
obvious what they do and almost impossible to use incorrectly.
This is worthwhile on its own just to make the usage clear, but the
real reason is that after this cleanup, it will be possible to remove
many extraneous calls to global critical edge splitting related to
cloning.
Mostly functionally neutral:
- may fix latent bugs.
- may reduce useless basic blocks after inlining.
This rewrite encapsulates the cloner's internal state, providing a
clean API for the CRTP subclasses. The subclasses are rewritten to use
the exposed API and extension points. This makes it much easier to
understand, work with, and extend SIL cloners, which are central to
many optimization passes. Basic SIL invariants are now clearly
expressed and enforced. There is no longer a intricate dance between
multiple levels of subclasses operating on underlying low-level data
structures. All of the logic needed to keep the original SIL in a
consistent state is contained within the SILCloner itself. Subclasses
only need to be responsible for their own modifications.
The immediate motiviation is to make CFG updates self-contained so
that SIL remains in a valid state. This will allow the removal of
critical edge splitting hacks and will allow general SIL utilities to
take advantage of the fact that we don't allow critical edges.
This rewrite establishes a simple principal that should be followed
everywhere: aside from the primitive mutation APIs on SIL data types,
each SIL utility is responsibile for leaving SIL in a valid state and
the logic for doing so should exist in one central location.
This includes, for example:
- Generating a valid CFG, splitting edges if needed.
- Returning a valid instruction iterator if any instructions are removed.
- Updating dominance.
- Updating SSA (block arguments).
(Dominance info and SSA properties are fundamental to SIL verification).
LoopInfo is also somewhat fundamental to SIL, and should generally be
updated, but it isn't required.
This also fixes some latent bugs related to iterator invalidation in
recursivelyDeleteTriviallyDeadInstructions and SILInliner. Note that
the SILModule deletion callback should be avoided. It can be useful as
a simple cache invalidation mechanism, but it is otherwise bug prone,
too limited to be very useful, and basically bad design. Utilities
that mutate should return a valid instruction iterator and provide
their own deletion callbacks.
This wasn't possible when the SIL cloner was first written, but subclass
existentials can involve generic classes, so you can have an opened
archetype type with a superclass constraint involving a type constraint.
I changed all of the places that used end_borrow_argument to use end_borrow.
NOTE: I discovered in the process of this patch that we are not verifying
guaranteed block arguments completely. I disabled the tests here that show this
bad behavior and am going to re-enable them with more tests in a separate PR.
This has not been a problem since SILGen does not emit any such arguments as
guaranteed today. But once I do the SILGenPattern work this will change.
rdar://33440767
This does not eliminate the entrypoints on SILBuilder yet. I want to do this in
two parts so that it is functionally easier to disentangle changing the APIs
above SILBuilder and changing the underlying instruction itself.
rdar://33440767
ConvertFunction and reabstraction thunks need this attribute. Otherwise,
there is no way to identify that withoutActuallyEscaping was used
to explicitly perform a conversion.
The destination of a [without_actually_escaping] conversion always has
an escaping function type. The source may have either an escaping or
@noescape function type. The conversion itself may be a nop, and there
is nothing distinctive about it. The thing that is special about these
conversions is that the source function type may have unboxed
captures. i.e. they have @inout_aliasable parameters. Exclusivity
requires that the compiler enforce a SIL data flow invariant that
nonescaping closures with unboxed captures can never be stored or
passed as an @escaping function argument. Adding this attribute allows
the compiler to enforce the invariant in general with an escape hatch
for withoutActuallyEscaping.
This flag supports promoting KeyPath access violations to an error in
Swift 4+, while building the standard library in Swift 3 mode. This is
only necessary as long as the standard library continues to build in
Swift 3 mode. Once the standard library build migrates, it can all be
ripped out.
<rdar://problem/40115738> [Exclusivity] Enforce Keypath access as an error, not a warning in 4.2.
When introducing SIL cloner support for substitution maps, I failed
to account for the separate handling of substitutions for opened
existentials. Perform this substitution when needed.
Fixes rdar://problem/39976572.
Substitution can be expensive; only do it when there might be something to
substitute. While here, use QueryTypeSubstitutionMapOrIdentity rather than
open-coding the same thing in a lambda.
Mandatory pass will clean it up and replace it by a copy_block and
is_escaping/cond_fail/release combination on the %closure in follow-up
patches.
The instruction marks the dependence of a block on a closure that is
used as an 'withoutActuallyEscaping' sentinel.
rdar://39682865
To mark when a user of it is known to escape the value. This happens
with materializeForSet arguments which are captured and used in the
write-back. This means we need to keep the context alive until after
the write-back.
Follow-up patches to fully replace the PostponedCleanup hack in SILGen
by a mandatory SIL transformation pass to guarantee the proper lifetime
will use this flag to be more conservative when extending the lifetime.
The problem:
%pa = partial_apply %f(%some_context)
%cvt = convert_escape_to_noescape [not_guaranteed] [escaped] %pa
%ptr = %materialize_for_set(..., %cvt)
... write_back
... // <-- %pa needs to be alive until after write_back
This statically guarantees that the access has no inner conflict within
its own scope.
IRGen will turn this into a "nontracking" access in which an
exclusivity check is performed for conflicts on an outer scope. However,
unlike normal accesses the runtime does not record the access, and the
access will not be checked for subsequent conflicts.
end_unpaired_access [no_nested_conflict] is not currently
supported. Making a begin_unpaired_access [no_nested_conflict] requires
deleting the corresponding end_unpaired_access. Future runtimes
could support this for verification by storing inline data in the
valud buffer. However, the runtime can never assume that a
[no_nested_conflict] begin_unpaired_access will have a corresponding
end_unpaired_access call without adding a new ExclusivityFlag for
that purpose.
Will be used to verify that withoutActuallyEscaping's block does not
escape the closure.
``%escaping = is_escaping_closure %closure`` tests the reference count. If the
closure is not uniquely referenced it prints out and error message and
returns true. Otherwise, it returns false. The returned result can be
used with a ``cond_fail %escaping`` instruction to abort the program.
rdar://35525730
This patch both makes debug variable information it optional on
alloc_stack and alloc_box instructions, and forced variable
information on debug_value and debug_value_addr instructions. The
change of the interface uncovered a plethora of bugs in SILGen,
SILTransform, and IRGen's LoadableByAddress pass.
Most importantly this fixes the previously commented part of the
DebugInfo/local-vars.swift.gyb testcase.
rdar://problem/37720555
@noescape function types will eventually be trivial. A
convert_escape_to_noescape instruction does not take ownership of its
operand. It is a projection to the trivial value carried by the closure
-- both context and implementation function viewed as a trivial value.
A safe SIL program must ensure that the object that the project value is based
on is live beyond the last use of the trivial value. This will be
achieve by means of making the lifetimes dependent.
For example:
%e = partial_apply [callee_guaranteed] %f(%z) : $@convention(thin) (Builtin.Int64) -> ()
%n = convert_escape_to_noescape %e : $@callee_guaranteed () -> () to $@noescape @callee_guaranteed () -> ()
%n2 = mark_dependence %n : $@noescape @callee_guaranteed () -> () on %e : $@callee_guaranteed () -> ()
%f2 = function_ref @use : $@convention(thin) (@noescape @callee_guaranteed () -> ()) -> ()
apply %f2(%n2) : $@convention(thin) (@noescape @callee_guaranteed () -> ()) -> ()
release_value %e : $@callee_guaranteed () -> ()
Note: This is not yet actually used.
Part of:
SR-5441
rdar://36116691
* Reduce array abstraction on apple platforms dealing with literals
Part of the ongoing quest to reduce swift array literal abstraction
penalties: make the SIL optimizer able to eliminate bridging overhead
when dealing with array literals.
Introduce a new classify_bridge_object SIL instruction to handle the
logic of extracting platform specific bits from a Builtin.BridgeObject
value that indicate whether it contains a ObjC tagged pointer object,
or a normal ObjC object. This allows the SIL optimizer to eliminate
these, which allows constant folding a ton of code. On the example
added to test/SILOptimizer/static_arrays.swift, this results in 4x
less SIL code, and also leads to a lot more commonality between linux
and apple platform codegen when passing an array literal.
This also introduces a couple of SIL combines for patterns that occur
in the array literal passing case.
