[cxx-interop] Use a synthesized C++ method when invoking a base metho…

[hyp]

…d from a derived class synthesized method

The use of a synthesized C++ method allows us to avoid making a copy of self when invoking the base method from Swift

[hyp]

@swift-ci please test

[hyp]

Still also should do that for field accessors.

[hyp]

@swift-ci please test linux platform

[hyp]

@swift-ci please test

[egorzhdan]

Awesome! 👍

[hyp]

@swift-ci please test

[hyp]

@swift-ci please test

[hyp]

@swift-ci please test

[hyp]

@swift-ci please test

[hyp]

@swift-ci please test source compatibility

[finagolfin]

It looks like this pull introduced 5 IRGen tests that assume a 64-bit platform, causing them to fail on Android armv7:

/home/ubuntu/jenkins/workspace/oss-swift-RA-linux-ubuntu-16.04-android/swift/test/Interop/Cxx/class/inheritance/fields-irgen.swift:13:11: error: CHECK: expected string not found in input
// CHECK: %[[ADD_PTR:.*]] = getelementptr inbounds i8, ptr %{{.*}}, i64 4
          ^
<stdin>:119:183: note: scanning from here
define linkonce_odr noundef i32 @_ZNK30CopyTrackedDerivedDerivedClass55__synthesizedBaseCall___synthesizedBaseGetterAccessor_xEv(ptr noundef nonnull align 4 dereferenceable(8) %this) #6 comdat align 2 {
                                                                                                                                                                                      ^
<stdin>:124:6: note: possible intended match here
 %add.ptr = getelementptr inbounds i8, ptr %this1, i32 4
     ^

@natecook1000, do these tests also fail on 32-bit watchOS, presuming that's still being tested by some CI?

[hyp]

Fixing it.

[hyp]

Patch up: #69283