Def-use Chains
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. A UD Chain generally means the assignment of some value to a variable. 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. 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. Purpose Making the use-define or define-use chains is a step in liveness analysis, so that logical representations of all the variables can be identified and tracked t ...
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