Module Interpreted_automata

module Interpreted_automata: sig .. end
An interpreted automaton is a convenient formalization of programs for abstract interpretation. It is a control flow graph where states are control point and edges are transitions. It keeps track of conditions on which a transition can be taken (guards) as well as actions which are computed when a transition is taken. It can then be interpreted w.r.t. the operational semantics to reproduce the behavior of the program or w.r.t. to the collection semantics to compute a set of reachable states.

This intermediate representation abstracts almost completely the notion of statement in CIL. Edges are either CIL expressions for guards, CIL instructions for actions or a return Edge. Thus, it saves the higher abstraction layers from interpreting CIL statements and from attaching guards to statement successors.



An interpreted automaton is a convenient formalization of programs for abstract interpretation. It is a control flow graph where states are control point and edges are transitions. It keeps track of conditions on which a transition can be taken (guards) as well as actions which are computed when a transition is taken. It can then be interpreted w.r.t. the operational semantics to reproduce the behavior of the program or w.r.t. to the collection semantics to compute a set of reachable states.

This intermediate representation abstracts almost completely the notion of statement in CIL. Edges are either CIL expressions for guards, CIL instructions for actions or a return Edge. Thus, it saves the higher abstraction layers from interpreting CIL statements and from attaching guards to statement successors.

type info = 
| NoneInfo
| LoopHead of int

Vertices are control points. When a vertice is the *start* of a statement, this statement is kept in vertex_stmt. Currently, this statement is kept for two reasons: to know when callbacks should be called and when annotations should be read.
type vertex = private {
   vertex_key : int;
   mutable vertex_start_of : Cil_types.stmt option;
   mutable vertex_info : info;
}
type assert_kind = 
| Invariant
| Assert
| Check
| Assume
type 'vertex labels = 'vertex Cil_datatype.Logic_label.Map.t 
Maps binding the labels from an annotation to the vertices they refer to in the graph.
type 'vertex annotation = {
   kind : assert_kind;
   predicate : Cil_types.identified_predicate;
   labels : 'vertex labels;
   property : Property.t;
}
type 'vertex transition = 
| Skip
| Return of Cil_types.exp option * Cil_types.stmt
| Guard of Cil_types.exp * guard_kind * Cil_types.stmt
| Prop of 'vertex annotation * Cil_types.stmt
| Instr of Cil_types.instr * Cil_types.stmt
| Enter of Cil_types.block
| Leave of Cil_types.block
Each transition can either be a skip (do nothing), a return, a guard represented by a Cil expression, a Cil instruction, an ACSL annotation or entering/leaving a block. The edge is annotated with the statement from which the transition has been generated. This is currently used to choose alarms locations.
type guard_kind = 
| Then
| Else
val pretty_transition : vertex transition
Pretty_utils.formatter
type 'vertex edge = private {
   edge_key : int;
   edge_kinstr : Cil_types.kinstr;
   edge_transition : 'vertex transition;
   edge_loc : Cil_types.location;
}
val pretty_edge : vertex edge Pretty_utils.formatter
module G: Graph.Sig.I 
  with type V.t = vertex
  and  type E.t = vertex * vertex edge * vertex
  and  type V.label = vertex
  and  type E.label = vertex edge
type graph = G.t 
type wto = vertex Wto.partition 
Weak Topological Order is given by a list (in topological order) of components of the graph, which are themselves WTOs
module Vertex: Datatype.S_with_collections  with type t = vertex
Datatype for vertices
module Edge: Datatype.S_with_collections  with type t = vertex edge

An interpreted automaton for a given function is a graph whose edges are guards and commands and always containing two special nodes which are the entry point and the return point of the function. It also comes with a table linking Cil statements to their starting and ending vertex
type automaton = {
   graph : graph;
   entry_point : vertex;
   return_point : vertex;
   stmt_table : (vertex * vertex)
Cil_datatype.Stmt.Hashtbl.t
;
}
module Automaton: Datatype.S  with type t = automaton
Datatype for automata
module WTO: sig .. end
val get_automaton : Cil_types.kernel_function -> automaton
Get the interpreted automaton for the given kernel_function without annotations

Get the wto for the automaton of the given kernel_function

val get_wto : Cil_types.kernel_function -> wto
Extract an exit strategy from a component, i.e. a sub-wto where all vertices lead outside the wto without passing through the head.
val exit_strategy : graph ->
vertex Wto.component -> wto
Output the automaton in dot format
val output_to_dot : Pervasives.out_channel ->
?number:[ `Stmt | `Vertex ] ->
?wto:wto -> automaton -> unit
type wto_index = vertex list 
the position of a statement in a wto given as the list of component heads
module WTOIndex: Datatype.S  with type t = wto_index
Datatype for wto_index
val get_wto_index : Cil_types.kernel_function ->
vertex -> wto_index
Returns the wto_index for a statement

the components left and the components entered when going from one index to another

val wto_index_diff : wto_index ->
wto_index ->
vertex list * vertex list
Returns the components left and the components entered when going from one vertex to another
val get_wto_index_diff : Cil_types.kernel_function ->
vertex ->
vertex ->
vertex list * vertex list
Returns wether v is a component head or not
val is_wto_head : Cil_types.kernel_function -> vertex -> bool
Returns wether v1,v2 is a back edge of a loop, i.e. if the vertex v1 is a wto head of any component where v2 is included. This assumes that (v1,v2) is actually an edge present in the control flow graph.
val is_back_edge : Cil_types.kernel_function ->
vertex * vertex -> bool
module Compute: sig .. end
This module defines the previous functions without memoization
module UnrollUnnatural: sig .. end

Dataflow computation: simple data-flow analysis using interpreted automata. This is mostly intended as an example for using interpreted automata; see also tests/misc/interpreted_automata_dataflow.ml for a complete example using this dataflow.
module type Domain = sig .. end
Input domain for a simple dataflow analysis.
module Dataflow: 
functor (D : Domain-> sig .. end
Builds a simple dataflow analysis over an input domain.