Wrong handling of equality/inequality operators by Data Flow Optimization

[cardillan]

This one is a bit embarrassing: the Data Flow Optimizer is meant to consider the expressions a < b identical to b > a, and a <= b identical to b >= a. In addition to this, it also considered a == b identical to b != a - I assumed that swapping the arguments and inverting the relation works without realizing it doesn't work for equality. Oops.

An example of the affected code is

inline def eval(b)
    b ? "true" : "false";
end;

inline def compare(a, b)
    print(eval(a == b), ", ", eval(a != b));
end;

compare("A", "A");

Due to the bug, this code prints "true, true" instead on "true, false".

There is also an unrelated bug in the processor emulator, which causes objects to be converted to the value 0 instead of 1. The processor emulator fortunately doesn't affect production code yet.

A fix will be coming shortly.