| 1 | .once
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| 2 |
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| 3 | .include "control-flow.dl"
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| 4 |
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| 5 | // Facts and Relations (Inputs)
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| 6 | // ============================
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| 7 |
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| 8 | // Objects can live in either local variables or object members.
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| 9 | .type Place = LocalVariable { f: Function, v: symbol }
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| 10 | | ObjectMember { o: symbol, m: symbol }
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| 11 |
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| 12 | // Places can be referenced by variables and object members.
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| 13 | .type Reference = VariableRef { v: symbol }
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| 14 | | MemberRef { o: symbol, m: symbol }
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| 15 |
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| 16 | // Variable (or object) `r` is allocated, or assigned a literal value, in
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| 17 | // statement `s` of `f`.
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| 18 | .decl define(f:Function, s:Statement, p:Place)
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| 19 | .input define
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| 20 |
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| 21 | // Reference `r` is assigned to a place `p` in statement `s` of `f`.
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| 22 | .decl assign(f:Function, s:Statement, p:Place, r:Reference)
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| 23 | .input assign
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| 24 |
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| 25 | // Place `a` is aliased by place `b`.
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| 26 | .decl alias(a: Place, b: Place)
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| 27 | .output alias
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| 28 |
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| 29 | // Rules and Outputs
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| 30 | // =================
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| 31 |
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| 32 | // `p` is implicitly defined when it is assigned to.
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| 33 | define(f, s, p) :- assign(f, s, p, _).
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| 34 |
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| 35 | // Simple aliasing with locals.
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| 36 | // a = ...
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| 37 | // b = a
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| 38 | alias($LocalVariable(f, a), $LocalVariable(f, b)) :-
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| 39 | define(f, s1, $LocalVariable(f, a)),
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| 40 | assign(f, s2, $LocalVariable(f, b), $VariableRef(a)),
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| 41 | CFGraph.reachable(f, s1, f, s2).
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| 42 |
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| 43 | // LocalVariables can also be aliased by object members. Note the special function name
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| 44 | // and statement number.
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| 45 | // a = ...
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| 46 | // b.m = a
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| 47 | alias($LocalVariable(f, a), $ObjectMember(b, m)) :-
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| 48 | define(f, s1, $LocalVariable(f, a)),
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| 49 | assign(f, s2, $ObjectMember(b, m), $VariableRef(a)),
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| 50 | CFGraph.reachable(f, s1, f, s2).
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| 51 |
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| 52 | // Objects members can be aliased too. Note the special function name and
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| 53 | // statement number.
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| 54 | // a.m = ...
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| 55 | // b = a.m
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| 56 | alias($ObjectMember(a, m), $LocalVariable(f, b)) :-
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| 57 | assign(f, _, $LocalVariable(f, b), $MemberRef(a, m)).
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| 58 | // a.m = ...
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| 59 | // b.m2 = a.m1
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| 60 | alias($ObjectMember(a, m1), $ObjectMember(b, m2)) :-
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| 61 | assign(_, _, $ObjectMember(b, m2), $MemberRef(a, m1)).
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| 62 |
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| 63 | // Inductive case.
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| 64 | alias(a, c) :- alias(a, b), alias(b, c).
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