[PATCH] D56587: Introduce DW_OP_LLVM_convert

[David Blaikie via Phabricator via llvm-commits]

dblaikie added a comment.

I'm a touch confused by the whole discussion here - so I'll write some things & perhaps folks can correct my understanding where necessary.

The issue is that a location expression (either in a direct location, or in a loclist) needs to reference a DIE.

Sounds like that DIE reference is necessarily CU-local (because we're talking about precomputing the offset - and we could only do that if it's CU-local).

We already emit other CU-local DIE references in attributes (eg: DW_AT_specification, etc) references with hardcoded 4 bytes in size- so why would it be problematic to emit this one in the same way (with a padded ULEB128 that we know will give us 4 bytes of offset to work with)?

& yeah, maybe if someone wants to save us some size (at the cost of whatever computational complexity this invokes in the assembler) it could be replaced with label differences (doing label differences for all DIE references would be nifty for manual editing/mucking about with DWARF, but not a big deal).


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  https://reviews.llvm.org/D56587/new/

https://reviews.llvm.org/D56587