[PATCH] D20206: GlobalsAA: Don't assume that intrinsics can't access global variables

[James Molloy via llvm-commits]

Hi,

Ah, I had forgotten we have argmemonly now. Yes, that sounds like the right
approach, but as Hal said I think the intrinsic list will need to be
audited.

James

On Thu, 12 May 2016 at 17:34 Daniel Berlin via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> On Thu, May 12, 2016 at 8:46 AM, Tom Stellard <thomas.stellard at amd.com>
> wrote:
>
>> tstellarAMD added a comment.
>>
>> In http://reviews.llvm.org/D20206#428381, @dberlin wrote:
>>
>> > So this is an interesting question.
>> >  Outside of very specific intrinsics (barriers), or intrinsics passed
>> global
>> >  variables, which intrinsics do you believe can affect global variables
>> and
>> >  why?
>>
>>
>> There probably aren't many besides barriers and maybe some of the cache
>> flushing intrinsics.
>>
>> > :)
>>
>> >
>>
>> > (Because if the answer is "none", we should probably make the ability to
>>
>> >  read/write non-passed-in globals an intrinsic property that folks have
>> to
>>
>> >  opt-in to)
>>
>>
>> My thinking is that is would be easier to treat intrinsics and functions
>> the same rather than having to add an attribute that makes intrinsics
>> behave like functions.
>
>
> Yes, sorry, didn't realize we could already use attributes on intrinsics,
> because i didn't look closely enough.
> This sounds like the right plan.
>
> There are already attributes like: readnone, readonly, argmemonly that can
>> be used to specify that an intrinsic won't access globals.  It doesn't seem
>> like it is too much trouble to ask people to use those for intrinsics, and
>> it looks like most intrinsics already are using these.
>>
>
> Yes, though i don't think GlobalsModRef is using argmemonly like it
> should, or at least, i don't see it.
>
>
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