* `users`: maps from a sequence of operands to a sequence of instructions
* `users(ofType:)` : as `users`, but filters users of a certain instruction type
* `Value.users`: = `Value.uses.users`
As the optimizer uses more and more AST stuff, it's now time to create an "AST" module.
Initially it defines following AST datastructures:
* declarations: `Decl` + derived classes
* `Conformance`
* `SubstitutionMap`
* `Type` and `CanonicalType`
Some of those were already defined in the SIL module and are now moved to the AST module.
This change also cleans up a few things:
* proper definition of `NominalTypeDecl`-related APIs in `SIL.Type`
* rename `ProtocolConformance` to `Conformance`
* use `AST.Type`/`AST.CanonicalType` instead of `BridgedASTType` in SIL and the Optimizer
The buffer of global arrays could already be statically initialized.
The missing piece was the array itself, which is basically a reference to the array buffer.
For example:
```
var a = [1, 2, 3]
```
ends up in two statically initialized globals:
1. the array buffer, which contains the elements
2. the variable `a` which is a single reference (= pointer) of the array buffer
This optimization removes the need for lazy initialization of such variables.
rdar://127757554
An object with tail allocated elements is in risk of being passed to malloc_size, which does not work for non-heap allocated objects.
Conservatively, disable objects with tail allocations.
rdar://121886093
```
let c = SomeClass()
```
is turned into
```
private let outlinedVariable = SomeClass() // statically initialized and allocated in the data section
let c = outlinedVariable
```
rdar://111021230
rdar://115502043
Also, make the ObjectOutliner work for OSSA. Though, it currently doesn't run in the OSSA pipeline.
Optionally, the dependency to the initialization of the global can be specified with a dependency token `depends_on <token>`.
This is usually a `builtin "once"` which calls the initializer for the global variable.
* add `NominalTypeDecl.isResilient`
* make the return type of `Type.getNominalFields` optional and return nil in case the nominal type is resilient.
This forces users of this API to think about what to do in case the nominal type is resilient.
Introduce two modes of bridging:
* inline mode: this is basically how it worked so far. Using full C++ interop which allows bridging functions to be inlined.
* pure mode: bridging functions are not inlined but compiled in a cpp file. This allows to reduce the C++ interop requirements to a minimum. No std/llvm/swift headers are imported.
This change requires a major refactoring of bridging sources. The implementation of bridging functions go to two separate files: SILBridgingImpl.h and OptimizerBridgingImpl.h.
Depending on the mode, those files are either included in the corresponding header files (inline mode), or included in the c++ file (pure mode).
The mode can be selected with the BRIDGING_MODE cmake variable. By default it is set to the inline mode (= existing behavior). The pure mode is only selected in certain configurations to work around C++ interop issues:
* In debug builds, to workaround a problem with LLDB's `po` command (rdar://115770255).
* On windows to workaround a build problem.
Codegen is the same, but `begin_dealloc_ref` consumes the operand and produces a new SSA value.
This cleanly splits the liferange to the region before and within the destructor of a class.
For example:
```
var p = Point(x: 10, y: 20)
let o = UnsafePointer(&p)
```
Also support outlined arrays with pointers to other globals. For example:
```
var g1 = 1
var g2 = 2
func f() -> [UnsafePointer<Int>] {
return [UnsafePointer(&g1), UnsafePointer(&g2)]
}
```
The `bare` attribute indicates that the object header is not used throughout the lifetime of the value.
This means, no reference counting operations are performed on the object and its metadata is not used.
The header of bare objects doesn't need to be initialized.
