Re: GCC optimizes integer overflow: bug or feature?

[Gabriel Dos Reis]

Paul Eggert <address@hidden> writes:

| Ian Lance Taylor <address@hidden> writes:
| 
| > We could disable VRP's assumptions about signed overflow.  I don't
| > know what else we could do to fix this case.  I don't even know how we
| > could issue a useful warning.  Perhaps there is a way.
| 
| It is a knotty problem.  Thanks for thinking about it.
| 
| I'm Handwaving with a capital H here, but one possibility is
| for plain -O2 to keep VRP, but disable its assumption about
| signed overflow when attempting to optimize away a
| comparison that comes directly from the user's code (as
| opposed to a comparison coming from subscript checking and
| the like).

If that is workable, it would be a good compromise.

-- Gaby