catastropher / optimizingcompiler Goto Github PK

All variables should be default initialized to 0 at the beginning of the first block so that one SSA definition for the variable always exists.

The dead code eliminator doesn't do analysis to determine the usage of arrays, so it's eliminating them all. So, we need to treat anything that has an array access (lvalues and expressions) as live in IoStatementFinder.

Input statements need to be considered variable assignments because the static analyzer doesn't understand that it changes the value of the variable. This is leading to incorrect optimizations. So, we need to create a new type of expression node and replace:
input X
with
let X = <input node>

Also:

• The code generator needs to understand let X = <input node> as scanf("%d", &X);
• IoStatementFinder needs to recognize let X = <input node> as IO so it doesn't get eliminated by the dead code eliminator