Homework 2

Due: start of class on Thursday, February 26th

• p.99 of PLP, Exercise 2.13, part (c). To clarify the grammar, you can replace the right-hand-side of rule 2 with cdr | a | b | c. If the left-hand-side of a rule is absent, it means that the left-hand-side is the same as the left-hand-side of the rule above it. If the right-hand-side is empty, it means that the left-hand-side matches with the empty string (we have also represented the empty string with an epsilon). ALSO ANSWER THESE QUESTIONS: Is this grammar amenable to LR parsing? Why or why not?
• p.152 of PLP, Exercise 3.4. The three examples have to show 3 fundamentally different ways for a live variable to be out of scope. Don't write down one example and then search/replace the variable names to come up with the other two.
• Take a look at the paper Array Bounds Check Elimination for the Java Hotspot Compiler by Thomas Wuerthinger, Christian Wimmmer, and Hanspeter Moessenboeck. Answer the following questions (hint: read Section 2 of the paper).
  1. What is the difference between the Hotspot Server JIT compiler and the Hotspot Client JIT compiler? Why do you need two versions?
  2. The Hotspot client compiler takes Java bytecode as input. That means that there is already a previous ("javac") phase that converted Java source into bytecode. How many intermediate forms does the bytecode go through on its way to becoming machine code? What are the names of these intermediate forms?
  3. Why is it helpful to have all these intermediate forms instead of going straight from Java source code to machine code?