Use-define chain
Data structure that tracks variable use and definitions / From Wikipedia, the free encyclopedia
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Within computer science, a use-definition chain (or UD chain) is a data structure that consists of a use U, of a variable, and all the definitions D of that variable that can reach that use without any other intervening definitions.[1][2] A UD Chain generally means the assignment of some value to a variable.
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A counterpart of a UD Chain is a definition-use chain (or DU chain), which consists of a definition D of a variable and all the uses U reachable from that definition without any other intervening definitions.[3]
Both UD and DU chains are created by using a form of static code analysis known as data flow analysis. Knowing the use-def and def-use chains for a program or subprogram is a prerequisite for many compiler optimizations, including constant propagation and common subexpression elimination.