Some dataflow analysis in Java
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README.md

Some code I wrote in 2011 to study the problem of dataflow analyses. All ideas were taken from the article Lecture Notes in Static Analysis by M.I.Schwartzbach.

The parser for the toy language "while" is implemented using the JavaCC parser generator. The dataflow analyzer is type-safe and implements a worklist solver algorithm. I implemented constraints for the simpler examples (initialized vars, liveness, sign).

Building

The AST nodes have to be compiled first:

cd language
ant jar
cd ..

Then the parser can be compiled:

cd parser
ant jar
cd ..

Then the analyzer code can be compiled:

ant jar

And finally, examples can be run:

ant liveness iv sign

Example

Here is the sign example input source:

var [x, y, z];
x=1;
y=0-2;
z=0;
x=10;
while (x>0) {
    x=x-1;
}

The parser turns this into AST which is transformed to CFG. Constraints for the CFG are then derived and the constraint system is produced:

[[exit]] = ALLJOIN([[x>0]])
[[entry]] = []
[[x>0]] = ALLJOIN([[x=10]],[[x=x-1]])
[[z=0]] = ALLJOIN([[y=0-2]]){z->eval(0)}
[[var [x, y, z]]] = ALLJOIN([[entry]]){z=null, y=null, x=null}
[[x=10]] = ALLJOIN([[z=0]]){x->eval(10)}
[[x=1]] = ALLJOIN([[var [x, y, z]]]){x->eval(1)}
[[x=x-1]] = ALLJOIN([[x>0]]){x->eval(x-1)}
[[y=0-2]] = ALLJOIN([[x=1]]){y->eval(0-2)}

All constraint variables are here in the form [[node name]]. After solving the system, node values are dumped:

entry = {}
var [x, y, z] = {z=null, y=null, x=null}
x=1 = {z=null, y=null, x=POS}
y=0-2 = {z=null, y=NEG, x=POS}
z=0 = {z=ZERO, y=NEG, x=POS}
x=10 = {z=ZERO, y=NEG, x=POS}
x=x-1 = {z=ZERO, y=NEG, x=TOP}
x>0 = {z=ZERO, y=NEG, x=TOP}
exit = {z=ZERO, y=NEG, x=TOP}

License

The MIT License (MIT)
Copyright (c) 2013 Raivo Laanemets

Permission is hereby granted, free of charge, to any person obtaining a copy of this software
and associated documentation files (the "Software"), to deal in the Software without restriction,
including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial
portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.