WebAlgorithm for computing reaching defs For each basic block B, we want to determine • REACHin(B): the set of defs reaching the entry of B • REACHout(B): the set of defs reaching the exit of B • To compute these, we use two pieces of information from B: – GEN(B): the set of defs which appear in B and may reach the exit of B. WebJul 10, 2024 · In compiler theory, a reaching definition for a given instruction is an earlier instruction whose target variable can reach (be assigned to) the given one without an intervening assignment. For example, in the following code: d1 : y := 3 d2 : x := y d1 is a reaching definition for d2.In the following, example, however: d1 : y := 3 d2 : y := 4 d3 : x := y
compiler construction - Special case of reaching definitions data …
WebReaching definitions §A definition d reaches a point P if there is a path from d to P such that d is the last definition of destalong that path. §More precise: A definition d reachesa point P if there is a path from d to P such that d is not killed along that path. §We are interested in alldefinitions that may reach point P §Remember: be conservative WebReaching Definitions Every assignment is a definition A definition d reaches a point p if there exists a path from the point immediately following d to p such that d is not killed … iras sponsorship gst
Ch 3.31: Reaching Definitions part-1 Compiler design ... - YouTube
WebConstant propagation is implemented in compilers using reaching definition analysis results. If all variable's reaching definitions are the same assignment which assigns a same constant to the variable, then the variable has a constant value and can be replaced with the constant. ... Muchnick, Steven S. (1997), Advanced Compiler Design and ... In compiler theory, a reaching definition for a given instruction is an earlier instruction whose target variable can reach (be assigned to) the given one without an intervening assignment. For example, in the following code: d1 is a reaching definition for d2. In the following, example, however: d1 is no … See more The similarly named reaching definitions is a data-flow analysis which statically determines which definitions may reach a given point in the code. Because of its simplicity, it is often used as the canonical example of a data … See more • Aho, Alfred V.; Sethi, Ravi & Ullman, Jeffrey D. (1986). Compilers: Principles, Techniques, and Tools. Addison Wesley. ISBN See more Reaching definition is usually calculated using an iterative worklist algorithm. Input: control-flow graph CFG = (Nodes, Edges, Entry, Exit) See more • Dead-code elimination • Loop-invariant code motion • Reachable uses See more WebReaching Definitions: Constraints • Define the constraints that a reaching definitions solution must satisfy: • gen[n] ⊆out[n]: if n generates a definition, the definition reaches the end of n • in[n] –kill[n] ⊆out[n]: if a definition reaches the start of n, and isn’t overwritten by n, then it reaches the end of n iras small company