[GR-56599] Create type units for types during debuginfo generation for referencing across multiple debug info files.

[graalvmbot]

Each type is currently generated within a compilation unit, with no way to reference it from outside the .debug_info section. During debuginfo generation at image runtime, we have to create a separate debuginfo file that references types generated during image build. This would require to reproduce debuginfo for types that was already created at image build.

One way to reference types in different objectfiles is to put them into so-called type units and create type signatures that can be used as references. Each type is placed in its own type unit and type references will be changed to refer to the type units. During the runtime debuginfo generation, we can then reference existing types by the type signature.

Type units were introduced in DWARF 4 in their own debugging section (.debug_types) and moved to the .debug_info section in DWARF 5 to reduce overhead. As a change to DWARF 5 requires little changes and makes creating type units more convenient, we will also update the DWARF version of the .debug_info section to DWARF 5.

[olpaw]

Hi @dominikmascherbauer

the PR is in good shape already. I only have a few questions before we can merge this:

• Did you check if this causes any regressions in debuginfo generation time of the image builder?
• Is it guaranteed that the classloader contributes to the type signatures for everything except primitive types?