Alias analysis

Alias analysis is a technique in compiler theory used to decide whether a storage location may be reached in more than one way. Two pointers are aliased when they point to the same location. A compiler that can show that two references cannot alias, or must alias, may rewrite code that uses them, for example replacing an expression with a constant, whereas when aliasing cannot be decided at compile time the code has to run as written, a case called may-alias. Analyses are usually classified by flow sensitivity and context sensitivity and may compute may-alias or must-alias information, and the term is often used interchangeably with points-to analysis, a specific case. In practice the program's memory is divided into alias classes, disjoint sets of locations that cannot alias one another, taken from types in a type-safe language or from allocations and address-taken variables in a flow-based analysis.