[llvm-commits] [llvm] r89434 - /llvm/trunk/lib/Analysis/CaptureTracking.cpp

[Duncan Sands]

Hi Dan,

> +      // Don't count comparisons of two pointers within the same object
> +      // as captures.
> +      if (I->getOperand(0)->getUnderlyingObject() ==
> +          I->getOperand(1)->getUnderlyingObject())

I think this bit is ok if you only do equality/inequality comparisons, but
is wrong if you allow inequality comparisons.  The reason is that this

     Q = GEP P, -n
     if (Q == null)
       break;

(see example from previous email) is equivalent to this

     Q = GEP P, -(n+1)
     if (Q > P)
       break;

and here you are comparing pointers with the same underlying object.

Ciao,

Duncan.