Not Working:

BB0:
   // %31 = phi i32* [ %.pre.i, %land.lhs.true.cleanup_crit_edge.i ], [ %26, %lor.lhs.false.i ]
BB1:
   // %33 = call i32 (...) @register_trav_edge1(i32* %.pre.i, i32* %31, i32 1, i32 16)

Working:
   // %31 = phi i32* [ %.pre.i, %land.lhs.true.cleanup_crit_edge.i ], [ %26, %lor.lhs.false.i ]
   // %33 = call i32 (...) @register_trav_edge1(i32* %.pre.i, i32* %31, i32 1, i32 16)

    bool isUsedInPhiInCurrentBB(llvm::Instruction * instr, llvm::PHINode * phi) {
        for (auto &I : *(instr->getParent())) {
            if (llvm::PHINode * bb_phi = dyn_cast<llvm::PHINode>(&I)) {
                for (int i = 0; i < bb_phi->getNumIncomingValues(); ++i) {
                    if (bb_phi->getIncomingValue(i) == dyn_cast<llvm::Value>(instr)) {
                        phi = bb_phi;
                        return true;
                    }
                }
            }
            else {
                break;
            }
        }

        return false;
    }

    int main() {
        llvm::PHINode * phi_source;
        if (llvm::Instruction * instr = dyn_cast<llvm::Instruction>(gdi.source)) {
            if (!dyn_cast<llvm::PHINode>(gdi.source)) {
                if (isUsedInPhiInCurrentBB(instr,phi_source)) {
                    gdi.source = dyn_cast<llvm::Value>(phi_source);
                }
            }
        }
    }