[PATCH] Don't ICE on symbolic ranges in VRP (PR tree-optimization/68455)

Marek Polacek polacek@redhat.com
Mon Nov 23 17:11:00 GMT 2015


On Mon, Nov 23, 2015 at 05:40:14PM +0100, Richard Biener wrote:
> On November 23, 2015 5:31:11 PM GMT+01:00, Marek Polacek <polacek@redhat.com> wrote:
> >We blow up on the following testcase because we find ourselves passing
> >[_13 + 1, INT_MAX] as a vr1 to extract_range_from_multiplicative_op_1;
> >that's bad because this function immediately calls vrp_int_const_binop
> >which just doesn't work for symbolic ranges, it only wants int_csts.
> >
> >This started with Richards S.'s changes in r228614 -- we're now since
> >able to recurse into SSA names, thus get better info about ranges.
> >That means that range_includes_zero_p in
> >extract_range_from_binary_expr_1
> >for the *_DIV_EXPR cases was able to determine that the range doesn't
> >include zero, so we went through a different code path and ended up
> >calling extract_range_from_multiplicative_op_1 even with symbolic
> >ranges.
> >
> >I couldn't come up with anything better than checking that we're
> >dealing
> >with nonsymbolic ranges for such a case.
> >
> >Bootstrapped/regtested on x86_64-linux, ok for trunk?
> 
> Hmm.  I think we can do better if vr0 is symbolical - use min, max for it.
> 
> I suppose it would be best to implement a get_integer_range () function doing that or also looking at equivalences if we are getting a symbolic range.
> 
> Anyway, those are future enhancements that shouldn't block this patch.
 
Is this something for this stage3?  Or should I open a PR and fix it in the
next stage1?

> Thus OK.

Thanks.

	Marek



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