07 Functions

07 Functions - Course Outline Introduction Control-flow...

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Unformatted text preview: Course Outline Introduction Control-flow analysis Dataflow analysis and abstract interpretation Sparse analysis Adding indirection (pointers) Adding functions Type- and constraint-based analysis Ben Hardekopf () CS 290C Program Analysis Fall 2011 1 / 49 Section Outline Functions Extending Lingo Control-flow Redux Context-Sensitive Analysis Functions + Pointers Ben Hardekopf () CS 290C Program Analysis Fall 2011 2 / 49 Extending Lingo with Functions Syntax n Z b B x Variable Op ::= + | - | * | / | < | < = | = | ! = | && | || e Exp ::= n | b | x | e e rhs Rhs ::= e | x 1 ( x 2 ,... ) c Cmd ::= c ; c | x := rhs | skip | while ( e ) do { c } | if ( e ) then { c } else { c } f FDef ::= def x 1 = fun ( x 2 ,... ) { c ; return x 3 } p Prog ::= c | f p Ben Hardekopf () CS 290C Program Analysis Fall 2011 3 / 49 Example Example (Lingo with Functions) def id = fun (p) { q := p ; return q } def main = fun (dummy_arg) { x := 1 ; y := 2 ; a := id(x) ; b := id(y) ; return dummy_arg } dummy := 0 ; result := main(dummy) Ben Hardekopf () CS 290C Program Analysis Fall 2011 4 / 49 Example Example (Lingo with Functions) def id = fun (p) { q := p ; return q } def main = fun (dummy_arg) { x := 1 ; y := 2 ; a := id(x) ; b := id(y) ; return dummy_arg } dummy := 0 ; result := main(dummy) For simplicity, we require: Functions have 1 parameter(s) and exactly one return statement Function arguments and return values are variables Function calls are only on the right-hand side of an assignment Ben Hardekopf () CS 290C Program Analysis Fall 2011 4 / 49 Section Outline Functions Extending Lingo Control-flow Redux Context-Sensitive Analysis Functions + Pointers Ben Hardekopf () CS 290C Program Analysis Fall 2011 5 / 49 Interprocedural Control-Flow Now that we have functions, we need to represent control-flow caused by function calls and function returns. There are two main choices: Call-Graph Interprocedural CFG Ben Hardekopf () CS 290C Program Analysis Fall 2011 6 / 49 Call-Graph Definition (Call-Graph) Formally, a call-graph G = ( N , E ) is: A set of nodes N , one for each function A set of edges E N N , such that x y iff function x contains a call to function y Ben Hardekopf () CS 290C Program Analysis Fall 2011 7 / 49 Call-Graph Definition (Call-Graph) Formally, a call-graph G = ( N , E ) is: A set of nodes N , one for each function A set of edges E N N , such that x y iff function x contains a call to function y This is a coarse representation of control-flow (there is no indication of how many calls exist in a function or where they occur). Note that: Unlike the CFG, control passes back from destination to source Cycles in the call-graph correspond to recursive functions Ben Hardekopf () CS 290C Program Analysis Fall 2011 7 / 49 Example Draw the call-graph for the following program: Program def id = fun (p) { q := p ; return q } x := 1 ; y := 2 ; a := id(x) ; b := id(y) Ben Hardekopf () CS 290C Program Analysis Fall 2011 8 / 49 Interprocedural Control-Flow...
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07 Functions - Course Outline Introduction Control-flow...

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