[embedded] Add support for (non-generic) classes in embedded Swift #68434
Conversation
- In embedded Swift, classes get a simplified metadata: Basically just a vtable + destructor + superclass pointer. - Only non-resilient (intended as permanent restriction), non-generic classes (for now) supported. - Relax the check that prohibits metadata emission and usage to allow classes.
|
@swift-ci please test |
| asImpl().noteStartOfImmediateMembers(theClass); | ||
|
|
||
| // Add vtable entries. | ||
| asImpl().addVTableEntries(theClass); |
There was a problem hiding this comment.
Do we want the full vtable?
There was a problem hiding this comment.
Can we be more lazy and just emit the methods that are used? Or are we assuming that lto will strip them?
There was a problem hiding this comment.
I'm actually assuming that SILOptimizer (namely PruneVTables and DeadFunctionElimination) will take care of that, because we can internalize public declarations in embedded Swift.
| void irgen::emitEmbeddedClassMetadata(IRGenModule &IGM, ClassDecl *classDecl, | ||
| const ClassLayout &fragileLayout) { | ||
| assert(!classDecl->isForeign()); | ||
| PrettyStackTraceDecl stackTraceRAII("emitting metadata for", classDecl); |
There was a problem hiding this comment.
Can you put this above the assertion? If the assertion fires, might be nice to have this diagnostic :)
| @@ -0,0 +1,32 @@ | |||
| // RUN: %target-swift-emit-ir %s -parse-stdlib -enable-experimental-feature Embedded -target arm64e-apple-none | %FileCheck %s | |||
There was a problem hiding this comment.
Test for calling methods?
| // RUN: %target-swift-emit-ir %s -parse-stdlib -enable-experimental-feature Embedded -target arm64e-apple-none | %FileCheck %s | ||
|
|
||
| // TODO: investigate why windows is generating more metadata. | ||
| // XFAIL: OS=windows-msvc |
There was a problem hiding this comment.
No investigation needed. This is because swift compiler sources doesn't run on windows.
|
@swift-ci please test |
| @@ -4967,6 +4973,36 @@ void irgen::emitClassMetadata(IRGenModule &IGM, ClassDecl *classDecl, | |||
| } | |||
| } | |||
|
|
|||
| void irgen::emitEmbeddedClassMetadata(IRGenModule &IGM, ClassDecl *classDecl, | |||
There was a problem hiding this comment.
Why do we need class embedded class metadata at all?
The vtable + pointer to superclass should provide everything which is needed for method dispatch and conditional down casting.
There was a problem hiding this comment.
You're right, and that's what this function is trying to do (to emit a simple metadata record with a vtable + superclass pointer), I think the only extra leftover is metadataBuilder.createMetadataAccessFunction(); which I'm removing in #68461
Add support for (non-generic) classes in embedded Swift