[llvm] [LLVM][DWARF] Add support for monolithic types in .debug_names (PR #68131)

[David Blaikie via llvm-commits]

dwblaikie wrote:

> > (not sure where it was recorded - maybe just in-person at LLVM dev)
> > @ayermolo did manage to find some data showing maybe a 10% memory regression for an IR->object compilation (where the backend memory usage isn't overshadowed by the frontend's peak) & I think is looking into it.
> 
> Yep. It's in the one of the threads in this PR. github is just hiding it under "load more". Plan is to re-factor not to rely on DIE post PR, pot that, and then update this code.

Not to duplicate conversations all over the place, but another thought I've had in other threads:

What if .debug_names entries referencing type units didn't have a `DW_IDX_die_offset` at all & relied on the type unit header to reference the type in the type unit? (is there anything else in a type unit we could be referencing? I don't think so... )

https://github.com/llvm/llvm-project/pull/68131