A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 3. DATAFLOW ANALYSIS 26
let varmap list combine (vml1 : varmap list) (vml2 : varmap list) : varmap list =
L.fold left varmap list combine one vml1 vml2
The function varmap list replace replaces the entry for a variable in the state, e.g.
assignment.
for an
let varmap list replace (vml : varmap list) (vm : varmap) : varmap list =
vm :: (L.remove assoc (id of vm vm) vml)
3.1.4 The oekind of an expression
These functions determine the oekind of CIL expressions by recursing over their sub-expressions.
We also use CIL's built-in constant folding to obtain constants for some expressions, e.g. SizeOf.
The function kind of int64 determine whether concrete integers are Odd or Even
let kind of int64 (i : Int64.t) : oekind =
let firstbit = Int64.logand i Int64.one in
if firstbit = Int64.one then Odd else Even
Depending on the abstract state, determine whether an expression e is for an Odd or Even integer.
The function oekind of exp uses CIL's constant folding function to deal with things like
sizeof(type). Mutually recursive functions descend into unary and binary operations. Non-integer
constants, addresses, and complex lvalues are translated as Top.
let rec oekind of exp (vml : varmap list) (e : exp) : oekind =
match e with
| Const(CInt64(i, , )) → kind of int64 i
| Lval(Var vi, NoOffset) → vml | > L.assoc vi.vid | > snd
| SizeOf | SizeOfE | SizeOfStr | AlignOf | AlignOfE →
e | > constFold true |> oekind of exp vml
| UnOp(uo, e, t) → oekind of unop vml uo e
| BinOp(bo, e1, e2, t) → oekind of binop vml bo e1 e2
| CastE(t, e) → oekind of exp vml e
| → Top
The function oekind of unop determines whether the result of unary operation is Odd or Even. If
the analysis were more clever, we could have said something about the LNot case, but for now we'll
just say Top.