+ // The lattice function may store more information on a PHINode than could be
+ // computed from its incoming values. For example, SSI form stores its sigma
+ // functions as PHINodes with a single incoming value.
+ if (LatticeFunc->IsSpecialCasedPHI(&PN)) {
+ LatticeVal IV = LatticeFunc->ComputeInstructionState(PN, *this);
+ if (IV != LatticeFunc->getUntrackedVal())
+ UpdateState(PN, IV);
+ return;
+ }
+