A program analysis may compute spurious information for a program with pointer variables, when the analysis uses alias information provided by efficient flow-insensitive alias analysis algorithms, because the program analysis cannot distinguish the alias relations that hold in a procedure when the procedure is invoked at a specific callsite. This paper presents a technique that determines whether a memory location might be accessed through a pointer dereference at a statement in a procedure when the procedure is invoked at a specific callsite. Empirical studies show that our technique may effectively improve the precision and efficiency of program analyses.