Module type Dataflow2.ForwardsTransfer

module type ForwardsTransfer = sig .. end

Interface to provide for a backward dataflow analysis.

val name : string

For debugging purposes, the name of the analysis

val debug : bool

Whether to turn on debugging

type t

The type of the data we compute for each block start. May be imperative.

val copy : t -> t

Make a deep copy of the data. Useful when Dataflow2.ForwardsTransfer.t is a mutable type. A copy of the data stored for a statement is made each time this statement is processed, just before Dataflow2.ForwardsTransfer.doStmt is called.

val pretty : Stdlib.Format.formatter -> t -> unit

Pretty-print the state.

val computeFirstPredecessor : Cil_types.stmt ->
       t -> t

computeFirstPredecessor s d is called when s is reached for the first time (i.e. no previous data is associated with it). The data d is propagated to s from an unspecified preceding statement s'. The result of the call is stored as the new data for s.

computeFirstPredecessor usually leaves d unchanged, but may potentially change it. It is also possible to perform a side-effect, for dataflows that store information out of the type t.

val combinePredecessors : Cil_types.stmt ->
       old:t ->
       t -> t option

Take some old data for the given statement, and some new data for the same point. Return None if the combination is identical to the old data, to signify that a fixpoint is currently reached for this statement. Otherwise, compute the combination, and return it.

val doInstr : Cil_types.stmt ->
       Cil_types.instr ->
       t -> t

The (forwards) transfer function for an instruction, internally called by Dataflow2.ForwardsTransfer.doStmt when the returned action is not SDone. The current location is updated before this function is called. The argument of type stmt is the englobing statement.

val doGuard : Cil_types.stmt ->
       Cil_types.exp ->
       t ->
       t Dataflow2.guardaction *
       t Dataflow2.guardaction

Generate the successors act_th, act_el to an If statement. act_th (resp. act_el) corresponds to the case where the given expression evaluates to zero (resp. non-zero). It is always possible to return GDefault, GDefault, especially for analyses that do not use guard information. This is equivalent to returning GUse d, GUse d, where d is the input state. A return value of GUnreachable indicates that this half of the branch will not be taken and should not be explored. stmt is the corresponding If statement, passed as information only.

val doStmt : Cil_types.stmt ->
       t ->
       t Dataflow2.stmtaction

The (forwards) transfer function for a statement. The (Cil.CurrentLoc.get ()) * is set before calling this. The default action is to do the instructions * in this statement, if applicable, and continue with the successors.

val doEdge : Cil_types.stmt ->
       Cil_types.stmt ->
       t -> t

what to do when following the edge between the two given statements. Can default to identity if nothing special is required.

module StmtStartData: Dataflow2.StmtStartData  with type data = t

For each statement id, the data at the start.