Specifically before this PR, if a caller did not customize a specific callback
of InstModCallbacks, we would store a static default std::function into
InstModCallbacks. This means that we always would have an indirect jump. That is
unfortunate since this code is often called in loops.
In this PR, I eliminate this problem by:
1. I made all of the actual callback std::function in InstModCallback private
and gave them a "Func" postfix (e.x.: deleteInst -> deleteInstFunc).
2. I created public methods with the old callback names to actually call the
callbacks. This ensured that as long as we are not escaping callbacks from
InstModCallback, this PR would not result in the need for any source changes
since we are changing a call of a std::function field to a call to a method.
3. I changed all of the places that were escaping inst mod's callbacks to take
an InstModCallback. We shouldn't be doing that anyway.
4. I changed the default value of each callback in InstModCallbacks to be a
nullptr and changed the public helper methods to check if a callback is
null. If the callback is not null, it is called, otherwise the getter falls
back to an inline default implementation of the operation.
All together this means that the cost of a plain InstModCallback is reduced and
one pays an indirect function cost price as one customizes it further which is
better scalability.
P.S. as a little extra thing, I added a madeChange field onto the
InstModCallback. Now that we have the helpers calling the callbacks, I can
easily insert instrumentation like this, allowing for users to pass in
InstModCallback and see if anything was RAUWed without needing to specify a
callback.
LifetimeChecker::shouldEmitError in order to avoid incorrectly
populating EmittedErrorLocs when no error is emitted.
This fixes a few corner cases where DI would error out or crash
while assigning to a wrapped property with a nonmutating setter.
It would be more abstractly correct if this got DI support so
that we destroy the member if the constructor terminates
abnormally, but we can get to that later.
In a constructor, SILGen lowers type(of: self) to a value_metatype
instruction, but 'self' might not have been initialized yet if
this is a convenience initializer, so we replace it with a use of
the 'self' metatype argument.
However getDynamicSelfMetadata() asserts if 'self' is a non-class
type. Since we know we're inside of a proper method here and not a
closure that captured 'self', we can use getSelfArgument() instead.
Fixes https://bugs.swift.org/browse/SR-12665 / rdar://problem/62481587.
DI had trouble with this pattern:
%s = struct_element_addr ...
%t0 = tuple_element_addr %s, 0
%t1 = tuple_element_addr %s, 1
%f = function_ref ...
apply %f(%t0, %t1)
This is because the NonLoadUses map only stored a single use of a
tuple element per instruction, preventing instructions such as
'apply' from being able to use multiple tuple elements.
In other cases where this comes up, such as with 'assign' and
'copy_addr', DI scalarizes the tuple operation by projecting
each component, however clearly this can't be easily done with
an 'apply'.
Instead, we can get DI out of the business of scalarization, at
least for instructions which are known to perform an unconditional
initialization.
We do this by changing the NonLoadUses map to store a vector of
DIMemoryUse IDs instead of a single value.
In a designated initializer of a non-root class, 'self' becomes
fully initialized after the 'super.init' call, at which point
escaping uses of 'self' become valid, and releases of 'self' are
lowered to a 'strong_release' instruction, which runs the
deinitializer.
In a root class, 'self' becomes fully initialized after all stored
properties have been initialized, at which point escaping uses of
'self' become valid.
However, DI would still lower a conditional destroy of 'self' by
destroying any initialized stored properties and freeing the object
with 'dealloc_partial_ref'. This is incorrect, because 'self' may
have escaped.
In the non-conditional destroy case, we correctly lowered the
release to a 'strong_release' if all stored properties are known
to be initialized.
Fix DI to handle the conditional destroy case by first checking if all
bits in the control variable are set, and releasing the instance with
'strong_release' if so. The 'dealloc_partial_ref' is only emitted
if not at least one stored property was not initialized.
This ensures that we don't deallocate an instance that may have
escaped.
Fixes <https://bugs.swift.org/browse/SR-13439>, <rdar://problem/67746791>,
<https://bugs.swift.org/browse/SR-13355>, <rdar://problem/67361228>.
While we don't need to destroy these fields, we still need to know
when the class is _semantically_ fully initialized, since this will
determine if we're going to release the class, running the deinitializer,
or if we're going to deallocate the memory for the instance directly.
Previously we would just forward the cleanup and create a normal "destroy"
cleanup resulting in early deallocation and use after frees along error paths.
As part of this I also had to tweak how DI recognizes self init writebacks to
not use SILLocations. This is approach is more robust (since we aren't relying
on SourceLocs/have verifiers to make sure we don't violate SIL) and also avoids
issues from the write back store not necessarily have the same SILLocation.
<rdar://problem/59830255>
This is achieved in 3 steps:
1. CSApply detects assignments to property wrappers inside constructors, and produces an `inout` expr instead of a `load`, which it normally would because nonmutating setters take the `self` by-value. This is necessary becasue the assign_by_wrapper instruction expects an address type for its $1 operand.
2. SILGenLValue now emits the assign_by_wrapper pattern for such setters, ignoring the fact that they capture `self` by value. It also introduces an additional load instruction for the setter patrial_apply because the setter signature still expects a value and we now have an address (because of (1)).
3. DefiniteInitialization specifically ignores load instructions used to produce a `self` value for a setter referenced on assign_by_wrapper because it will be deleted by lowering anyway.
Resolves rdar://problem/60600911 and rdar://problem/52280477
This commit eliminates the need for mark uninitialized fixup by updating the
compiler so that we now emit:
```
%0 = alloc_box
%1 = mark_uninitialized %0
%2 = project_box %1
...
destroy_value %1
```
Instead of:
```
%0 = alloc_box
%1 = project_box %0
%2 = mark_uninitialized %1
...
destroy_value %0
```
Now that the first type of code is generated, I can change project_box to only
take guaranteed arguments. This will ensure that the OSSA ARC optimizer can
eliminate copies of boxes without needing to understand the usage of the
project_box.
This is going to let me change getUninitializedValue() to special case alloc_box
so that we return the project_box (the address we want to analyze) rather than
the mark_uninitialized (which is on the box).
Specifically isDefiniteInitFinished is always set to false and
TreatAddressToPointerAsInout is set to true when ever DI is run, so this patch
just constant propagates those values and then DCEs as appropriate.
and eliminate dead code. This is meant to be a replacement for the utility:
recursivelyDeleteTriviallyDeadInstructions. The new utility performs more aggresive
dead-code elimination for ownership SIL.
This patch also migrates most non-force-delete uses of
recursivelyDeleteTriviallyDeadInstructions to the new utility.
and migrates one force-delete use of recursivelyDeleteTriviallyDeadInstructions
(in IRGenPrepare) to use the new utility.
The XXOptUtils.h convention is already established and parallels
the SIL/XXUtils convention.
New:
- InstOptUtils.h
- CFGOptUtils.h
- BasicBlockOptUtils.h
- ValueLifetime.h
Removed:
- Local.h
- Two conflicting CFG.h files
This reorganization is helpful before I introduce more
utilities for block cloning similar to SinkAddressProjections.
Move the control flow utilies out of Local.h, which was an
unreadable, unprincipled mess. Rename it to InstOptUtils.h, and
confine it to small APIs for working with individual instructions.
These are the optimizer's additions to /SIL/InstUtils.h.
Rename CFG.h to CFGOptUtils.h and remove the one in /Analysis. Now
there is only SIL/CFG.h, resolving the naming conflict within the
swift project (this has always been a problem for source tools). Limit
this header to low-level APIs for working with branches and CFG edges.
Add BasicBlockOptUtils.h for block level transforms (it makes me sad
that I can't use BBOptUtils.h, but SIL already has
BasicBlockUtils.h). These are larger APIs for cloning or removing
whole blocks.
This flag is set by DefinitInitialization if the lifetime of the stored value is controlled dynamically.
If the flag is set, it's not (easily) possibly to statically calculate the lifetime of the stored value.
With the advent of dynamic_function_ref the actual callee of such a ref
my vary. Optimizations should not assume to know the content of a
function referenced by dynamic_function_ref. Introduce
getReferencedFunctionOrNull which will return null for such function
refs. And getInitialReferencedFunction to return the referenced
function.
Use as appropriate.
rdar://50959798
This will make the forthcoming CanonicalizeInstruction interface more
clear.
This is generally the better approach to utilities that mutate the
instruction stream. It avoids the temptation to assume that only a
single instruction will be deleted or that only instructions before
the current iterator will be deleted. This often happens to work but
eventually fails in the presense of debug and end-of-scope
instructions.
A function returning an iterator has a more clear contract than one
accepting some iterator reference of unknown
providence. Unfortunately, it doesn't work at the lowest level of
utilities, such as recursivelyDeleteTriviallyDeadInstructions, where
we want to handle instruction batches.
This undoes some of Joe's work in 8665342 to add a guarantee: if an
@objc convenience initializer only calls other @objc initializers that
eventually call a designated initializer, it won't result in an extra
allocation. While Objective-C /allows/ returning a different object
from an initializer than the allocation you were given, doing so
doesn't play well with some very hairy implementation details of
compiled nib files (or NSCoding archives with cyclic references in
general).
This guarantee only applies to
(1) calling `self.init`
(2) where the delegated-to initializer is @objc
because convenience initializers must do dynamic dispatch when they
delegate, and Swift only stores allocating entry points for
initializers in a class's vtable. To dynamically find an initializing
entry point, ObjC dispatch must be used instead.
(It's worth noting that this patch does NOT check that the calling
initializer is a convenience initializer when deciding whether to use
ObjC dispatch for `self.init`. If we ever add peer delegation to
designated initializers, which is totally a valid feature, that should
use static dispatch and therefore should not go through objc_msgSend.)
This change doesn't /always/ result in fewer allocations; if the
delegated-to initializer ends up returning a different object after
all, the original allocation was wasted. Objective-C has the same
problem (one of the reasons why factory methods exist for things like
NSNumber and NSArray).
We do still get most of the benefits of Joe's original change. In
particular, vtables only ever contain allocating initializer entry
points, never the initializing ones, and never /both/ (which was a
thing that could happen with 'required' before).
rdar://problem/46823518
In Swift 5 mode, 'self' in a convenience init has a DynamicSelfType, so
the value_metatype instruction returns a DynamicSelfType metatype.
However, the metatype argument to the constructor is a plain class metatype
because it's an interface type, so we have to "open" it by bitcasting it
to a DynamicSelfType.
Fixes <https://bugs.swift.org/browse/SR-9430>, <rdar://problem/46982573>.
This was done early on during the split of predictable mem opts from DI. This
has been done for a long time, so eliminate the "Ownership" basename suffix.
When building on Windows, the std::string being passed will on the
stack, where the destructor will be invoked before the return, nil'ing
out reference. This causes incorrect behaviour when building the
diagnostic or FIXITs. Explicitly create the StringRef to prevent the
std::string from being invalidated.
Compiler passes that intermingle analysis with mutation of the CFG
are fraught with danger. The bug here was that a single AssignInst
could appear twice in DI's Uses list, once as a store use and once
as a load use.
When processing Uses, we would lower AssignInsts on the fly. We would
take care to erase the instruction pointer from the current Use, but
if a subsequent Use *also* referenced the now-deleted AssignInst, we
would crash.
Handle this in the standard way: instead of lowering assignments
right away, just build a list of assignments that we're planning on
lowering and process them all at the very end.
This has the added benefit of simplifying the code, because we no
longer have to work as hard to keep the state of the Uses list
consistent while lowering AssignInsts. The rest of DI should not
care that the lowering got postponed either, since it was already
expected to handle any ordering of elements in the Uses list, so
it could not assume that any particular AssignInst has been lowered.
Fixes <https://bugs.swift.org/browse/SR-9451>.
On Windows at least, the std::string associated with the name of the
property would be copy constructed before being passed to the diagnostic
engine. The resultant DiagnosticArgument in the InFlightDiagnostic
would hold a StringRef to the copy-constructed std::string. However,
because the arguments are inalloca'ed on Windows, the copy constructed
string would be destructed before the return of the argument.
Fortunately, this would result in the standard library overwriting the
string and the use-after-free would fail to print the argument.
Explicitly construct the StringRef before passing the name to the
diagnostic to avoid the use-after-free.
