[cfe-dev] motivations for approaches to macros in Index/IndexingAction.cpp ?

[James Widman via cfe-dev]

On Mon, May 20, 2019 at 5:32 PM Jan Korous <jkorous at apple.com> wrote:
>
> Hi James,
>
> The current implementation of this hashing function ignores some cases. We're in the process of upstreaming the whole index-while-building feature to LLVM project and decided to fix this by temporarily using trivial implementation - just hashing the full bitcode representation of index record. Eventually we need a new implementation that is both correct and performant - so far the idea was to explore the possibility of using the existing ODR violation hasher for this purpose.

Ok, so... I guess "correct and performant" means "yes, we do want to
incorporate macro definitions & expansions in the future", in which
case I'm looking forward to it! (:

separate topic, under "performance": it seems like it would be good if
declarations & definitions of entities with external linkage were not
represented as "occurrences", because currently, if I want to get the
locations of all such decls, it seems like I need to visit all
"occurrences", which seems like a lot of extra work if the user ends
up visiting only two translation units. (And currently, doing this for
an index-store for the clang & llvm source code takes about 11.5
seconds on my macbook.)

In other words, upon loading the index-store, I need to know the
locations of all external decls & defs for the whole program (because
the user should be able to jump to any of those from the outset, from
any TU), but it seems like loading for all *other* occurrences could
be done more lazily.

I don't know where this topic fits in the pipeline of design
discussions for upstreaming index-while-building tho.

--James