CS322 Prog Lang & Compilers                      Prog Assignment #1
Assigned Wednesday April 5, 2007.        Due Monday, April 10, 2007

This assignment is to extend the program discussed in class for
translating Arithmetic expressions to IR code. The extension is to
evaluate binary operators in a manner that decreases the number of
registers needed. The rule of thumb is that given a binary operator
(exp1 + exp2) we should first translate the sub expression (either
exp1 or exp2) that is more demanding. I.e. we should translate first
the sub expression that when translated will require the most
registers.


1) Download the files "S02code.sml" and "ProgramTypes.sml". Links to
these can be found on the notes web page.

2) Create a compiler manager sources file "Prog1.cm" and get the two
files to compile (as is) first. Look at the notes from lecture 1, if
you need help getting started.

3) Now write and add the function "demand"

fun demand x =
case node of
  Var(loc,x) => . . .
| Binop(m,x,y) => . . .
| Literal(loc,Cint n) => . . .

This function returns an int, which is the number of registers
needed to translate the expression "x". You will need to study the
function "expr" (from file "S02code.sml") to be sure you get the
right answer.  Even though the type "expression" has many more
constructors than "Var", "Binop", and "Literal". You need only
handle these three cases.  The function "demand" will be recursive.

4) Use the function "demand" to recode the "Binop" case of "expr" so
that the sub-expression with greatest demand is translated first.

5) Test your programs by using the function "trans" (in file
"S02code.sml"). Consult the text book (Section 7.3.1 pp 315-318) for
ideas about how to construct good tests.

WHAT TO HAND IN
A) Print out the code of S02code.sml. Circle in colored ink the
additions you made to the code.

B) Also hand in a copy your compile-manager sources file.

C) Run your tests, and print and hand in a transcript of the testing.

EXPECTATIONS and EVALUATION
A) I expect you to be able to write "demand" (30%)
B) I expect you to be able to modify "expr"  (30%)
C) I expect a good set of tests.             (20%)
D) I expect you to use the compile-manager   (10%)
E) I expect neat well designed and elegant   (10%)
   code that is well documented. I expect
   you to document the code I wrote as well
   as the code you wrote.