[LLVMdev] AliasAnalysis as a Loadable Module, Possible 2.6->2.7 issue

[Will Dietz]

Hi John,

Thank you very much for your reply and explanation.  This was indeed
my issue and fixes it nicely.

Have a good one,

~Will

On Wed, May 26, 2010 at 9:09 AM, John Criswell <criswell at illinois.edu> wrote:
> Dear Will,
>
> If you're seeing the wrong method executed, it's probably because you're
> using multiple inheritance in your analysis group (which is a very common
> thing to do).
>
> LLVM 2.7 made a change which alleviated the need for RTTI or some other
> undesirable C++ feature.  However, it also broke multiple inheritance with
> analysis group passes.  To fix it, your analysis group needs to implement a
> getAdjustedAnalysisPointer() method.  The implementation should look
> something like this:
>
> /// When chaining analyses, changing the pointer to the correct pass
> virtual void *getAdjustedAnalysisPointer(const PassInfo *PI) {
>   if (PI->isPassID(&ArrayBoundsCheckGroup::ID))
>       return (ArrayBoundsCheckGroup*)this;
>   return this;
> }
>
> Just replace "ArrayBoundsCheckGroup" with whatever the name of your analysis
> group is, and it should work.
>
> -- John T.
>
>
> Will Dietz wrote:
>>
>> Thanks for the response, Eli.
>>
>> The header suggestion could certainly cause this issue (I panicked for
>> a second), but unfortunately as far as I can tell the headers are in
>> fact from LLVM 2.7.
>>
>> The pass is built as a project configured by llvm, so hopefully that
>> would make things right, but also:
>> --include paths look legit (make VERBOSE=1, etc)
>> --strace on the build process for the project confirms no headers
>> outside the llvm 2.7 tree are read, and 'svn diff' confirms I haven't
>> managed to botch those.
>>
>> The code is from the "release_27" branch, for what it's worth.
>>
>> I'm not at all convinced I haven't somehow broken my build
>> environment, but it's not clear to me how.
>>
>> Thoughts on anything else I could look into?
>>
>> For what it's worth, attached is the project triggering the issue, if
>> someone gets bored and either wants to try it or tell me what I'm
>> doing wrong :).
>>
>> Thanks for your time,
>>
>> ~Will
>>
>> On Tue, May 25, 2010 at 10:13 PM, Eli Friedman <eli.friedman at gmail.com>
>> wrote:
>>
>>>
>>> On Tue, May 25, 2010 at 5:53 PM, Will Dietz <willdtz at gmail.com> wrote:
>>>
>>>>
>>>> Hi all,
>>>>
>>>> First time posting to llvmdev, be gentle :).
>>>>
>>>> I'm working on an AliasAnalysis implementation and running into an
>>>> issue on 2.7, that doesn't exist in 2.6 as far as I can tell.
>>>>
>>>> Short version: has anyone been able to load an AliasAnalysis module
>>>> into 2.7's opt?
>>>>
>>>> Longer version:
>>>>
>>>> Even with a dummy pass implementation (just returns MayAlias for
>>>> everything), I'm getting very strange behavior:
>>>>
>>>> All calls to FooAA::alias go to FooAA::print, resulting in
>>>> understandably painful failure thereafter, generally a segfault.
>>>>
>>>
>>> Are you sure you built your module against LLVM 2.7 headers?
>>>
>>> -Eli
>>>
>>
>> >
>
>