IRGen: Emit objc type encoding for ivars

[kastiglione]

ObjC ivar metadata has up to now emitted an empty string for the ivar's objc type encoding. Conversely, ObjC property metadata is emitted with an objc type encoding. This changes the compiler to also emit an objc type encoding for ivars.

The motivation for this change is for lldb to print ivars of classes declared in Objective-C but implemented in Swift, as defined in SE-0436. Without the presence of type encoding for ivars, lldb is unable to present to the user the ivars/properties of instances of such classes.

rdar://138569299

[kastiglione]

@swift-ci test

[kastiglione]

@swift-ci test

[kastiglione]

@swift-ci test

[mikeash]

LGTM, although I'm not the one to judge IRGen style or logic.

[kastiglione]

@swift-ci test macOS

[kastiglione]

@swift-ci test

[kastiglione]

@swift-ci test

[kastiglione]

@rjmccall the code I'm changing was authored by you, although that was 12 years ago. Tagging you in case you have feedback.

[rjmccall]

LGTM.

Would you be interested in also fixing the TODOs about putting these in a proper section? I think this is just a matter of generalizing the useOSLogSection parameter on getAddrOfGlobalString to an enum.

Actually, there's an existing enum for this, ObjCLabelType. It probably ought to be renamed to StringLiteralKind and given an explicit CString enumerator, but it all looks pretty straightforward.

[kastiglione]

On further testing, this needs changes for bridged types. A property declared NSString and defined as String, cannot use an encoding of @, as a String is a struct and not a class.

My initial plan is to use ? as the encoding for the handful of classes which bridge to Swift structs.

[kastiglione]

@swift-ci test

[kastiglione]

@swift-ci test macOS

[kastiglione]

@mikeash I've made a change here around bridged types such as String. See #81967 (comment) and 17499e4. Any thoughts?

[mikeash]

Looks right to me. The type isn't representable in this form so ? is the right way to indicate that.

[kastiglione]

@swift-ci test

[kastiglione]

@swift-ci test macOS