Draw a concise AST for the following tiger expression, label each node
with the "result register" attribute for the Sethi-Ullman register
allocation algorithm, show the resulting code, AND break the HERA
instructions into "basic blocks". By now, the first three of these
steps should be familiar for everything except "if" and "<", so
hopefully much of that will go quickly and you can focus on these new
kinds of nodes and on the creation of basic blocks. You can spend up
to 30 minutes on this one, to make sure you have time to engage the
new stuff.

    if 0 then
       if 1
       then 2
       else 3
    else
       41 + (3<4)