Decision tree

[zoltan-mihalyi]

Example with variables:

var a = 1, b = 1;
if (x1) {
  a = 2;
  b = 2;
  if (x2) {
    a++;
    b++;
  }
}
if (x3) {
  a = 3;
  b = 3;
}
return a === b; //optimize to true

Example without variables:

(x ? 1 : 0) * 0; // 0, if x has no side effect

The steps to evaluate a === b are:

• Evaluate a:
  • Find decision points (x1,x2,x3) affecting "a" and build a tree-like data structure.
  • Iterate the tree and create a map of possible values where decision list is the key.
• Evaluate b like a.
• Evaluate a === b:
  • Merge the possible values map of "a" and "b".
  • Iterate the merged decision map.
  • Create a new map by evaluating with "a" and "b" values.