The main point of this change is to make sure that a shared function always has a body: both, in the optimizer pipeline and in the swiftmodule file.
This is important because the compiler always needs to emit code for a shared function. Shared functions cannot be referenced from outside the module.
In several corner cases we missed to maintain this invariant which resulted in unresolved-symbol linker errors.
As side-effect of this change we can drop the shared_external SIL linkage and the IsSerializable flag, which simplifies the serialization and linkage concept.
The main change is to rename DeadFunctionElimination -> DeadFunctionAndGlobalElimination, because the pass is now also doing dead-global elimination.
A second change is to remove the FunctionLivenessComputation base class. It’s not used anywhere else.
It makes sense to to this in a single pass, because there might be dead cycles for globals and functions, e.g. if a global references a function in its static initializer and the function references that global.
Another improvement: eliminate dead global-initializers. Before we had an explicit SIL representation of statically initialized globals, we had to keep them alive.
rdar://32956923
If we know that we have a FunctionRefInst (and not another variant of FunctionRefBaseInst), we know that getting the referenced function will not be null (in contrast to FunctionRefBaseInst::getReferencedFunctionOrNull).
NFC
This attribute allows to define a pre-specialized entry point of a
generic function in a library.
The following definition provides a pre-specialized entry point for
`genericFunc(_:)` for the parameter type `Int` that clients of the
library can call.
```
@_specialize(exported: true, where T == Int)
public func genericFunc<T>(_ t: T) { ... }
```
Pre-specializations of internal `@inlinable` functions are allowed.
```
@usableFromInline
internal struct GenericThing<T> {
@_specialize(exported: true, where T == Int)
@inlinable
internal func genericMethod(_ t: T) {
}
}
```
There is syntax to pre-specialize a method from a different module.
```
import ModuleDefiningGenericFunc
@_specialize(exported: true, target: genericFunc(_:), where T == Double)
func prespecialize_genericFunc(_ t: T) { fatalError("dont call") }
```
Specially marked extensions allow for pre-specialization of internal
methods accross module boundries (respecting `@inlinable` and
`@usableFromInline`).
```
import ModuleDefiningGenericThing
public struct Something {}
@_specializeExtension
extension GenericThing {
@_specialize(exported: true, target: genericMethod(_:), where T == Something)
func prespecialize_genericMethod(_ t: T) { fatalError("dont call") }
}
```
rdar://64993425
We were not using the primary benefits of an intrusive list, namely the
ability to insert or remove from the middle of the list, so let's switch
to a plain vector. This also avoids linked-list pointer chasing.
The differentiation transform does the following:
- Canonicalizes differentiability witnesses by filling in missing derivative
function entries.
- Canonicalizes `differentiable_function` instructions by filling in missing
derivative function operands.
- If necessary, performs automatic differentiation: generating derivative
functions for original functions.
- When encountering non-differentiability code, produces a diagnostic and
errors out.
Partially resolves TF-1211: add the main canonicalization loop.
To incrementally stage changes, derivative functions are currently created
with empty bodies that fatal error with a nice message.
Derivative emitters will be upstreamed separately.
Add ExecuteSILPipelineRequest which executes a
pipeline plan on a given SIL (and possibly IRGen)
module. This serves as a top-level request for
the SILOptimizer that we'll be able to hang
dependencies off.
... including all SIL functions with are transitively referenced from such witness tables.
After the last devirtualizer run witness tables are not needed in the optimizer anymore.
We can delete witness tables with an available-externally linkage. IRGen does not emit such witness tables anyway.
This can save a little bit of compile time, because it reduces the amount of SIL at the end of the optimizer pipeline.
It also reduces the size of the SIL output after the optimizer, which makes debugging the SIL output easier.
This is needed for cross-module-optimization: CMO marks functions as inlinable. If a private or internal method is referenced from such an inlinable function, it must not be eliminated by dead function elimination after serialization (a method is basically an AbstractFunctionDecl).
For SILFunctions we can do this by simply setting the linkage, but for methods we need another mechanism.
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.
We used to look at the vtable entry's linkage to determine if the
vtable entry was dead, in case the vtable entry linkage was more
visible than the method being overridden.
This hack is no longer needed now that a method override more
visible than its base introduces a new vtable entry.
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 normalizes the creation of pass pipelines by ensuring that all pass
pipelines take a SILOption instead of only some. It also makes it so that we do
not need to propagate options through various pipeline creation helpers.
SILWitnessTable::Entry already contains a superset of what was supported
by SILDefaultWitnessTable::Entry, the latter of which only had “no entry”
and “method” states. Make SILDefaultWitnessTable::Entry an alias for
SILWitnessTable::Entry, and unify all of the parsing/printing/
(de)serialization logic.
SIL will not generate calls to protocol requirements that override
other protocol requirements, so all of the witness table entries for
the overriding arguments are dynamically dead. Remove them from the
witness tables entirely.
Implements rdar://problem/43870489, reducing the size of the standard
library binary by 196k.
ClassDecl::getSuperclass() produces a complete interface type describing the
superclass of a class, including any generic arguments (for a generic type).
Most callers only need the referenced ClassDecl, which is (now) cheaper
to compute: switch those callers over to ClassDecl::getSuperclassDecl().
Fixes an existing test for SR-5993.
The other side of #17404. Since we don't want to generate up front key path metadata for properties/subscripts with no withheld implementation details, the client should generate a key path component that can be used to represent a key path component based on its public interface.
* SILModule::isVisibleExternally utility for VarDecls.
* Fix the SIL parser so it doesn't drop global variable decls.
This information was getting lost in SIL printing/parsing.
Some passes rely on it. Regardless of whether passes should rely on it,
it is totally unacceptable for the SIL passes to have subtle differences
in behavior depending on the frontend mode. So, if we don't want passes
to rely on global variable decls, that needs to be enforced by the API
independent of how the frontend is invoked or how SIL is serialized.
* Use custom DemangleOptions to lookup global variable identifiers.
Client code can make a best effort at emitting a key path referencing a property with its publicly exposed API, which in the common case will match what the defining module would produce as the canonical key path component representation of the declaration. We can reduce the code size impact of these descriptors by not emitting them when there's no hidden or possibly-resiliently-changed-in-the-past information about a storage declaration, having the property descriptor symbol reference a sentinel value telling client key paths to use their definition of the key path component.
This will allow key paths to resiliently reference public properties from other binaries by referencing a descriptor vended by the originating binary. NFC yet, this just provides printing/parsing/verification of the new component.
@_silgen_name and @_cdecl functions are assumed to be referenced from
C code. Public and internal functions marked as such must not be deleted
by the optimizer, and their C symbols must be public or hidden respectively.
rdar://33924873, SR-6209
