some modification in cal.l
a sub-list go through function tested.
liveness anylize tested.
do not delete test files
heuristic_live() added.
3addr to ssa tested.
rm unused var in SSA form
cse completed.
cse tested.
copy elimination tested.
color rocks!
code elimination almost done.
a better heuristic elimination.
fix a bug in get_liveness() and add pesudo-code for print. Looks pretty good now.
dead code elimination added.
use unary minus instead of assignment as the pesudo-print code.
a bug fixed, using explicit pseudo-print operator instead.
CE/CSE and DE should be looped untill a fixed-point is reached.
ddg graph environment, ddg construction/printing tested.
DDG weight assignment function tested.