'Flow functions' diaporamas de présentation

Pointer Analysis

Pointer Analysis. Pointer Analysis. Outline: What is pointer analysis Intraprocedural pointer analysis Interprocedural pointer analysis Andersen and Steensgaard New Directions. Pointer and Alias Analysis. Aliases : two expressions that denote the same memory location.

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Worklist algorithm

Worklist algorithm. Initialize all d i to the empty set Store all nodes onto a worklist while worklist is not empty: remove node n from worklist apply flow function for node n update the appropriate d i , and add nodes whose inputs have changed back onto worklist. Worklist algorithm.

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CSE 231 : Advanced Compilers

CSE 231 : Advanced Compilers. Building Program Analyzers. dataflow analysis. http://blog.ezyang.com/2011/04/hoopl-dataflow-lattices/. http://blog.ezyang.com/2011/04/hoopl-dataflow-lattices/. http://lambda-the-ultimate.org/node/3557.

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Pointer analysis

Pointer analysis. Pointer Analysis. Outline: What is pointer analysis Intraprocedural pointer analysis Interprocedural pointer analysis Andersen and Steensgaard. Pointer and Alias Analysis. Aliases: two expressions that denote the same memory location. Aliases are introduced by: pointers

815 views • 52 slides

Dataflow analysis

Dataflow analysis. Dataflow analysis: what is it?. A common framework for expressing algorithms that compute information about a program Why is such a framework useful?. Dataflow analysis: what is it?. A common framework for expressing algorithms that compute information about a program

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Another example

Another example. p := &x; *p := 5 y := x + 1;. Another example. p := &x; *p := 5 y := x + 1;. x := 5; *p := 3 y := x + 1;. ???. Another example. for j := 1 to N for i := 1 to M a[i] := a[i] + b[j]. Another example. for j := 1 to N for i := 1 to M

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Administrative stuff

Administrative stuff. Office hours: After class on Tuesday. 1: x := ... 2: y := ... 3: y := ... 4: p :=. ... x ... 5: x := ... ... y. ... x ... 6: x := ... 7: *p :=. ... x ... ... y ... 8: y :=. Worklist algorithm. Initialize all d i to the empty set

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Recap: Reaching defns algorithm

Recap: Reaching defns algorithm. From last time: reaching defns worklist algo We want to avoid using structure of the domain outside of the flow functions. Will use lattices!. while (worklist.empty.not) do let n := worklist.remove_any; let info_in := m(n.incoming_edges);

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Intraprocedural Points-to Analysis

Intraprocedural Points-to Analysis. Flow functions:. Pointers to dynamically-allocated memory. Handle statements of the form: x := new T One idea: generate a new variable each time the new statement is analyzed to stand for the new location:. Example. l := new Cons. p := l. t := new Cons.

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Formalization of DFA using lattices

Formalization of DFA using lattices. Recall worklist algorithm. let m: map from edge to computed value at edge let worklist: work list of nodes for each edge e in CFG do m(e) := ; for each node n do worklist.add(n) while (worklist.empty.not) do let n := worklist.remove_any;

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Constraints for reaching definitions

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Termination

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Lub and glb

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Constraints for reaching definitions

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Dataflow analysis

Dataflow analysis. Dataflow analysis: what is it?. A common framework for expressing algorithms that compute information about a program Why is such a framework useful?. Dataflow analysis: what is it?. A common framework for expressing algorithms that compute information about a program

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Components of representation

Components of representation. Control dependencies: sequencing of operations evaluation of if & then side-effects of statements occur in right order Data dependencies: flow of definitions from defs to uses operands computed before operations

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Review of topics

Review of topics. Final exam : May 2nd to May 7 th Projects due on May 7th. Modeling. Finite-state models (Kripke structures) Symbolic modeling of transition systems: Boolean variables Transitions described logically Semantics of the Kripke structure generated

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