[LLVMdev] Removing types from metadata

[Duncan P. N. Exon Smith]

> On Fri, Dec 19, 2014 at 10:59 AM, Tom Stellard <tom at stellard.net> wrote:
> Hi,
> 
> Types were recently removed from metadata in the IR, which means older
> LLVM IR code with metadata won't compile.  Was this intentional?
> Is there a practical way to maintain compatibility with older LLVM IR?
> 
> Thanks,
> Tom

As Reid said, there's no backwards compatibility for assembly.  However,
I did share an upgrade script (as mentioned in r224257) that should help
you update out-of-tree testcases (or other IR).  Have a look at the
attachment to PR21532.

Warning: Reid noticed that the `sed -E` flag I'm using there doesn't
seem to be portable.  You might have to fiddle with the regexes (please
share if you do).

> On 2014-Dec-19, at 11:40, Reid Kleckner <rnk at google.com> wrote:
> 
> That said, if it's just a matter of skipping over the 'metadata' token, it would be nice to let old IR assemble.

It's a little harder than that, since it's a `Type` token, but in
theory it's probably doable.

However, I think this would set a bad precedent.  There's nowhere else
(that I know of) where we accept two versions of assembly.  The
LLParser is relatively easy to work with because it doesn't have that
kind of historical baggage.