Make SILLInkage available in SIL as `SIL.Linkage`.
Also, rename the misleading Function and GlobalVariable ABI `isAvailableExternally` to `isDefinedExternally`
In lazy typechecking mode, errors in the program may only be discovered during
SILGen, which can leave the SIL in a bad state for subsequent stages of
compilation. If errors were detected, skip SIL verification and optimization to
prevent knock-on failures.
Partially reverts https://github.com/swiftlang/swift/pull/75428, which included
a more targeted fix for one of the possible knock-on effects of bad SIL coming
out of SILGen.
Resolves rdar://132107752.
The main changes are:
*) Rewrite everything in swift. So far, parts of memory-behavior analysis were already implemented in swift. Now everything is done in swift and lives in `AliasAnalysis.swift`. This is a big code simplification.
*) Support many more instructions in the memory-behavior analysis - especially OSSA instructions, like `begin_borrow`, `end_borrow`, `store_borrow`, `load_borrow`. The computation of end_borrow effects is now much more precise. Also, partial_apply is now handled more precisely.
*) Simplify and reduce type-based alias analysis (TBAA). The complexity of the old TBAA comes from old days where the language and SIL didn't have strict aliasing and exclusivity rules (e.g. for inout arguments). Now TBAA is only needed for code using unsafe pointers. The new TBAA handles this - and not more. Note that TBAA for classes is already done in `AccessBase.isDistinct`.
*) Handle aliasing in `begin_access [modify]` scopes. We already supported truly immutable scopes like `begin_access [read]` or `ref_element_addr [immutable]`. For `begin_access [modify]` we know that there are no other reads or writes to the access-address within the scope.
*) Don't cache memory-behavior results. It turned out that the hit-miss rate was pretty bad (~ 1:7). The overhead of the cache lookup took as long as recomputing the memory behavior.
The result of a store_borrow can "escape" to other access bases, like a "pointer" access base.
Then a store-borrow access base is _not_ distinct from such another base.
It's dangerous to continue walking over an `unchecked_addr_cast` which casts between two different types.
We can only do this if the result is known to be the end of the walk, i.e. the cast result is not used in a relevant way.
We need to compare the not lowered types, because function types may differ in their original version but are equal in the lowered version, e.g.
```
((Int, Int) -> ())
(((Int, Int)) -> ())
```
Fixes a miscompile
We need to ignore such casts because otherwise the constructed walking path wouldn't contain the right `existential` field kind.
Fixes a miscompile caused by redundant load elimination.
rdar://132364917
Invalid types are not considered Escapable. This makes it difficult to make any
assumptions about nonescapable types.
Fixes rdar://132348528 (Fix LifetimeDependenceDiagnostics to handle invalid SIL types)
These projections don't have access scopes, so the utility was treating them
like escapes.
Fixes: rdar://131499478 (Difficulties composing non-escapable types)
