[poolalloc] r177097 - When finding the target of a function call, get the called value and strip

[David Blaikie]

On Thu, Mar 14, 2013 at 1:12 PM, John Criswell <criswell at illinois.edu> wrote:
> On 3/14/13 2:00 PM, David Blaikie wrote:
>>
>> On Thu, Mar 14, 2013 at 11:49 AM, John Criswell <criswell at uiuc.edu> wrote:
>>>
>>> Author: criswell
>>> Date: Thu Mar 14 13:49:29 2013
>>> New Revision: 177097
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=177097&view=rev
>>> Log:
>>> When finding the target of a function call, get the called value and
>>> strip
>>> pointer casts instead of asking the CallSite class to do that.  This
>>> fixes a
>>> bug in which DSA crashes on calls to functions when the function is
>>> subjected
>>> to a ConstantExpr bitcast first.
>>
>> Test case?
>
>
> The test case from the user contains a simple bitcode file and an LLVM pass
> that *uses* DSA that triggers the bug.  It is not clear to me that the
> existing DSA passes trigger the bug.
>
> I can add the pass to the poolalloc sub-project and create a lit test for
> it, but given the triviality of the fix and my limited bandwidth, it's
> pretty low on my priority list.
>
> If you insist on having a test case, I'll try to devise one, but I really
> don't think it's worth the time.

I'm hardly in a position to insist, let alone on a subproject I've
never contributed to - just like to be clear on why test cases are
omitted when they are.

It sounds like it might be a case where an (API-level) unit test could
be used, but it probably lies somewhere between the scenario tests
(which can't reach it since they don't have the pass you mentioned) &
a unit test (where it'd probably take too much code to build a one-off
test/IR/etc to exercise the code path)

Thanks for the details,

- David

>
> -- John T.
>
>
>>
>>> Patch contributed by Fan Long.
>>>
>>> Modified:
>>>      poolalloc/branches/release_32/lib/DSA/DSGraph.cpp
>>>
>>> Modified: poolalloc/branches/release_32/lib/DSA/DSGraph.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/poolalloc/branches/release_32/lib/DSA/DSGraph.cpp?rev=177097&r1=177096&r2=177097&view=diff
>>>
>>> ==============================================================================
>>> --- poolalloc/branches/release_32/lib/DSA/DSGraph.cpp (original)
>>> +++ poolalloc/branches/release_32/lib/DSA/DSGraph.cpp Thu Mar 14 13:49:29
>>> 2013
>>> @@ -569,8 +569,13 @@ DSCallSite DSGraph::getDSCallSiteForCall
>>>         }
>>>       }
>>>
>>> -  // Add a new function call entry...
>>> -  if (Function *F = CS.getCalledFunction())
>>> +  //
>>> +  // Add a new function call entry.  We get the called value from the
>>> call site
>>> +  // and strip pointer casts instead of asking the CallSite class to do
>>> that
>>> +  // since CallSite::getCalledFunction() returns 0 if the called value
>>> is
>>> +  // a bit-casted function constant.
>>> +  //
>>> +  if (Function
>>> *F=dyn_cast<Function>(CS.getCalledValue()->stripPointerCasts()))
>>>       return DSCallSite(CS, RetVal, VarArg, F, Args);
>>>     else
>>>       return DSCallSite(CS, RetVal, VarArg,
>>>
>>>
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>
>