[llvm-dev] RFC: Drop support for old style scalar TBAA

[Sanjoy Das via llvm-dev]

On Tue, Nov 8, 2016 at 8:31 AM, Duncan P. N. Exon Smith
<dexonsmith at apple.com> wrote:
> Seems like a nice cleanup to me!
>
>> On 2016-Nov-07, at 13:01, Sanjoy Das via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>
>> Hi all,
>>
>> I want to clarify / emphasize two things based on an off-list
>> conversation:
>>
>> - The bitcode and IR parser both auto upgrade old style TBAA to the
>>   newer TBAA struct tags.
>
> Shouldn't we drop the textual IR auto-upgrade?  I'd rather fail in the verifier, since we don't aim for textual IR compatibility anyway.  (Could be done as follow-up, and it would be nice to attach an upgrade script to a PR or on the list or something.)

Honestly, the upgrade code is simple enough that I don't think it's a
net win to delete.

What I can do is make the textual IR tbaa auto-upgrade controlled by
an off by default option.  That way you get the stricter behavior by
default but you can flip back to the gentler behavior if you'd rather
not edit all your IR files now.

What do you think?
-- Sanjoy