On Tue, May 27, 2014 at 11:59 AM, Eric Botcazou <ebotca...@adacore.com> wrote: >> I'm asking to merge them (move them to fold_comparison). > > OK, I'll repost a first patch doing only the fold-const.c massaging. > >> Yeah, it would be nice to see some support. The most interesting cases >> will be symbolic-singleton +- CST where the offset shrinks a constant offset >> in a symbolic A +- CST (thus we don't get into any overflow issues). Thus >> handling >> >> [a + 1, a + 1] - [1, 1] -> [a, a] >> >> for example. We get the offsetted singleton symbolic ranges from >> conditional asserts a lot. > > For the case at hand, you have [x + 1, INF] for y and you want to evaluate the > range of y - x, so you really don't want to use the range of x...
Ok. That's similar to the issue I try to address with the VRP snipped I posted yesterday. I'd say we still handle "basic" symbolic range ops in extract_range_from_binary_1 but in extract_range_from_binary_expr for a symbolic op0 we try to simplify it with both [op1, op1] and with the value-range of op1 until we get a non-varying range as result. Not sure if it's worth restricting that to the case where op0s value-range refers to op1 or vice versa, and eventually only use op1 symbolically then. Richard. > -- > Eric Botcazou
