[PATCH] D30785: [DWARF] Versioning for DWARF constants; verify FORMs

[Robinson, Paul via llvm-commits]

> -----Original Message-----
> From: aprantl at apple.com [mailto:aprantl at apple.com]
> Sent: Thursday, April 20, 2017 10:33 AM
> To: David Blaikie
> Cc: reviews+D30785+public+750a0f0570653e04 at reviews.llvm.org; Robinson,
> Paul; clayborg at gmail.com; llvm-commits at lists.llvm.org; nhaehnle at gmail.com
> Subject: Re: [PATCH] D30785: [DWARF] Versioning for DWARF constants;
> verify FORMs
> 
> 
> > On Apr 20, 2017, at 10:20 AM, David Blaikie <dblaikie at gmail.com> wrote:
> >
> > Also, Adrian - still curious to hear if you have any thoughts about
> /where/ that check should go (see the review history discussing failing
> when the attribute is added, rather than later when the abbreviation is
> created) as well as how it should be implemented (assert V report fatal,
> etc)
> 
> IIUC the main concern about putting it into the Abbreviation creation is
> that it might be expensive to get at the DWARF version of the CU.  I'm not
> sure how expensive it is going to be, but if this is in an !NDEBUG path
> only, perhaps the extra cost can be justified. That said, if it turns out
> to add a noticeable delay to our RA stage2 bots, then the code as it is in
> this review now is the right trade-off.
> 
> -- adrian

A more significant concern was that it required (or at least, that's what
I came up with) virtual methods, which makes the DIE class bigger, which
could be a significant memory consumption problem.  For a debugging check,
that seems like too much cost (because it also is a cost in release mode).
--paulr