CS 375, Compilers: Example Questions for Final Exam

Addressing:

     type complex = record  re, im: real  end;

          item  = record name:      alfa;
                         age:       integer;
                         location:  complex;
                         displayed: boolean;
                         color:     array[(red,green,blue)] of integer;
                         link:      ^item;
                         cost:      real     end;

     var items = array [ 8..12, (low, med, hi), 7..11] of item;

• If integer and boolean are 4 bytes and alfa, pointers, and real are 8 bytes, how much storage is used by the array items?
• Show the intermediate code for the expression:

     items[10, hi, 8].link^.color[blue]
  

  Show how it was derived and give the aref form.

Other Questions:

• A robot moves on a square grid. The robot can go forward (f), turn left (l), or turn right (r). Give a grammar to describe the language of all sequences of moves that leave the robot pointing in the same direction as when it started.
• What kind of grammar is the above (in the Chomsky hierarchy)?
• Describe a kind of local optimization.
• Describe what it means for a subexpression to be (a) available, (b) busy, (c) killed.
• Describe sources of extra run-time overhead in (a) time and (b) space in an object-oriented language.
• Draw boxes around the following code to show the basic blocks:

     n := k*2;
     if n < j then write('less')
              else begin k := k - 1; write('more') end;
     writeln(k);
  

  Number the blocks and draw a flow graph; give the matrix form of the flow graph and its transitive closure.
• Give an advantage and a disadvantage for (a) call by reference (b) call by value.
• What are the most important things to optimize in a scientific program? Why?
• Give three examples of computer architecture innovations that require compiler innovations to be effective.
• Briefly and clearly define the following terms: ... 20 terms chosen from the vocabulary list on the study guide.