[Dwarf-discuss] Alternative to 250130.1 (index valued DW_AT_object_pointer): LEB128 relative DIE offsets

[David Blaikie]

As an alternative to the indexed proposal in 250130.1, which proposes
allowing a constant classed value for DW_AT_object_pointer, as an index
into the formal parameters of the subprogram, I was wondering how folks
would feel about something a bit different:

What about a reference classed form that is a (signed) LEB128 relative DIE
offset - relative to the start of the DIE containing the attribute value?

This would allow for other shortenings of DIEs that are commonly nearby.

I don't have measurements on how much it could decrease DWARF size, but
could maybe prototype such a thing (bit expensive, because it makes DWARF
byte size dependent on itself in some ways - and LLVM's DWARF generation
precomputes DIE offsets, etc, rather than relying on assembler relaxation)

- Dave
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