Before this commit, the TwosComplementArithmeticNormalizationPass wasn't
taking into consideration properly all the cases where the arithmetic
can wrap around in case of expression such as (x + const1 <=> const2) or
(x - const1 <=> const 2).
This caused 2 different classes of problems that affected semantics.
1) In some cases we were emitting comparisons that were too broad,
meaning that they were true in a larger set of cases than the
original one.
2) In other cases we were emitting tautological comparisons, i.e.
comparisons that were always demonstrably true or false at compile
time.
This commit fixes the problem, treating all the cases in a generalized
unique way that works correctly for every case.
Implements transforms when the results of sub or add with a constant
operand are compared against constant:
1) x + a == b --> x == b - a
2) x + a != b --> x != b - a
3) x + a <= b --> x <= b - a
4) x + a < b --> x < b - a
5) x + a >= b --> x >= b - a
6) x + a > b --> x > b - a
After the transformation, the right hand side is also enqued for
analysis to detect opporunities to use unary minus if a-b is a negative
constant.
Change company name to "rev.ng Labs Srl" in all license headers
to reflect changed company name and legal status
Add missing license headers to files that didn't have one
Valentina Sona