[PATCH] D69886: [DebugInfo] Support for DW_OP_implicit_pointer (Post IR transformation phase)

[David Blaikie via Phabricator via llvm-commits]

dblaikie added a comment.

Apologies for not having enough time to review this in more detail at the moment, so this feedback is shorting from the hip slightly based on reading the existing conversations and patch description

Broadly:

I'd expect more than 3 patches and in this order:

1. Backend/DWARF emission support for new debug info IR/metadata/intrinsic usage/DW_OP operators. This should include tests with hand-crafted IR (or generated from future patches - but I think this should be narrow enough that a small example could be given mostly with IR generated from clang/LLVM, and only a minor edit to use the new feature)

2-N) Individual patches, one for each optimization that generates this new representation where possible/useful - each one of these patches should be independent and include tests for the change (tests that are IR->IR tests, testing only the specific optimization)

(the 2-N patches can't come before (1) or the trunk would be broken by passes generating IR that the DWARF backend could not handle)

@probinson @aprantl - do you folks know why implicit_pointer needs to point to another DIE, rather than describing bytes directly? I guess it's intended to handle void*, for instance? (where the type information for the pointee isn't present in the pointer type) But for something like int* if the int isn't in memory (so can't be pointed to) - say, it's in a register, I'd expect to describe the value of the int without any extra DIE references, etc? (who knows if the DIE is in a variable/described by any other DIE). I'm pretty confused by the way this DWARF feature is spec'd & wondering if we should avoid implementing it/instead implement a better extension? But quite possible there's things about the design that I don't understand.


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https://reviews.llvm.org/D69886