Constant Record Propagation

Introduction

The purpose of this assignment is to become familiar with the constant propagation implementation by extending it in some places. In this assignment you will extend the constant propagation with propagation of constant records and evaluation of field access on constant records.

In the partial-eval package you will find a Tiger-PE-ConstProp module. This module is currently just a copy of the constant propagation implementation in the Tiger Compiler. You should extend the code in this module (and maybe other modules) in this exercise.

You can use the tiger-pe tool to test your implementation. This tool is a source to source transformation wrapping the the Tiger-Partial-Eval tool. This tool currently just invokes constant propagation, but you will change this into a partial evaluator later.

Example

Invoking your solution on the Tiger program

  let type intlist = {hd: int, tl: intlist}
  
      var tail : intlist := nil
      var list : intlist :=
        intlist{
          hd = 12,
          tl = intlist { hd = 13, tl = tail}}
  
   in printint(list.tl.hd)
  end

should for example result in

  let type intlist = {hd : int, tl : intlist}
   in printint(13)
  end

Notice that the type declaration is no longer required in this example, but it is included in this example because the dead code eliminator in de Tiger Compiler will not remove it.

Installation

Download the package for the partial evaluator assignment:

• partial-eval-0.3.tar.gz

The package should be configured, build and installed with the following commands, which assumes that you want to install the tools in the `pwd` :

  ./configure --prefix=`pwd` --with-xt=/usr --with-tiger=/usr
  make bootclean
  make
  make install

make bootclean removes intermediate C files that are distributed in typical StrategoXT? packages. This is required to create new dependecy files for Tiger-Partial-Eval.

You should install the tools before you run them. Running on a build package will not work or will not reflect your latest changes.

Running your tools

Run the constant propagator with:

  tiger-pe -i some-test.tig

Notice that tiger-pe has some useful switches for debugging: --elim-dead off will ommit the dead code elimination, --ensugar off will not ensugar and --pp off will not pretty print the Tiger AST.

Tips

See the Tiger Language topic if you need information on Tiger.

Notice that a field access on a constant record is not allowed in Tiger. You will have to implement the evaluation of field accesses before you can run the output of your tool with run-tiger .

For more information on partial evaluation in general visit the Partial Evaluation topic on the Program Transformation Wiki.

-- MartinBravenboer - 06 Feb 2003