[llvm-commits] [llvm] r162098 - in /llvm/trunk: lib/Analysis/MemoryBuiltins.cpp test/Transforms/InstCombine/objsize.ll

[Benjamin Kramer]

On 17.08.2012, at 19:47, Eli Friedman <eli.friedman at gmail.com> wrote:

> On Fri, Aug 17, 2012 at 7:16 AM, Benjamin Kramer
> <benny.kra at googlemail.com> wrote:
>> Author: d0k
>> Date: Fri Aug 17 09:16:37 2012
>> New Revision: 162098
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=162098&view=rev
>> Log:
>> Guard MemoryBuiltins against self-looping GEPs, which can occur in unreachable code due to constant propagation.
>> 
>> Fixes PR13621.
>> 
>> Modified:
>>    llvm/trunk/lib/Analysis/MemoryBuiltins.cpp
>>    llvm/trunk/test/Transforms/InstCombine/objsize.ll
>> 
>> Modified: llvm/trunk/lib/Analysis/MemoryBuiltins.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/MemoryBuiltins.cpp?rev=162098&r1=162097&r2=162098&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Analysis/MemoryBuiltins.cpp (original)
>> +++ llvm/trunk/lib/Analysis/MemoryBuiltins.cpp Fri Aug 17 09:16:37 2012
>> @@ -473,6 +473,10 @@
>> }
>> 
>> SizeOffsetType ObjectSizeOffsetVisitor::visitGEPOperator(GEPOperator &GEP) {
>> +  // Ignore self-referencing GEPs, they can occur in unreachable code.
>> +  if (&GEP == GEP.getPointerOperand())
>> +    return unknown();
> 
> What happens when you have two GEPs referencing each other?

I've wondered about this too, but can it really happen?

I'm also not sure how to integrate a visited set into the instvisitor.

- Ben