A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 3. DATAFLOW ANALYSIS 24
The function varmap list pretty uses the functions string of varmap list and Pretty.text
to convert a varmap list to a doc:
let varmap list pretty () (vml : varmap list) =
vml | > string of varmap list | > text
3.1.3 Functions for manipulating kinds and states
Now, we must dene some functions that manipulate lists of varmaps, culminating in the functions
varmap list combine and varmap list replace. varmap list combine nds the least-upperbound
of two varmap lists. This function is responsible for determining the abstract state of the
program at a join point. varmap list replace adds or replaces a mapping from the varmap list.
It is used in the transfer function for assignments.
The function oekind neg gets the opposite kind:
let oekind neg (k : oekind) : oekind =
match k with
| Even → Odd
| Odd → Even
| → k
The function varmap equal checks if two varmap's are exactly the same:
let varmap equal (vm1 : varmap) (vm2 : varmap) : bool =
(id of vm vm1) = (id of vm vm2) ∧
(kind of vm vm1) = (kind of vm vm2)
The function varmap list equal checks that two varmap lists are exactly the same. We sort the
lists rst because order doesn't matter.
let varmap list equal (vml1 : varmap list) (vml2 : varmap list) : bool =
let sort = L.sort (fun (id1, ) (id2, ) → compare id1 id2) in
list equal varmap equal (sort vml1) (sort vml2)
The function oekind includes denes the partial order for our lattice:
• Bottom, Odd, Even < Top
• Bottom < Odd, Even
• But Even Odd