not (currently) defined on SNaN's. However, in the second example, we can make
a more aggressive assumption: because the undef is allowed to be an arbitrary
value, we are allowed to assume that it could be zero. Since a divide by zero
-it has <em>undefined behavior</em>, we are allowed to assume that the operation
+has <em>undefined behavior</em>, we are allowed to assume that the operation
does not execute at all. This allows us to delete the divide and all code after
it: since the undefined operation "can't happen", the optimizer can assume that
it occurs in dead code.