------- Comment #19 from dberlin at gcc dot gnu dot org 2006-04-24 01:10
-------
Subject: Re: [4.2 Regression]
25_algorithms/prev_permutation/1.cc on powerpc{64,}-linux and
powerpc-darwin
On Sun, 2006-04-23 at 23:14 +0000, pinskia at gcc dot gnu dot org wrote:
>
> ------- Comment #17 from pinskia at gcc dot gnu dot org 2006-04-23 23:14
> -------
> Rewritting that loop like:
> [kudzu:local/trunk/gcc] pinskia% svn diff tree-ssa-loop-niter.c
> Index: tree-ssa-loop-niter.c
> ===================================================================
> --- tree-ssa-loop-niter.c (revision 113199)
> +++ tree-ssa-loop-niter.c (working copy)
> @@ -1939,6 +1939,7 @@ scev_probably_wraps_p (tree type, tree b
> tree unsigned_type, valid_niter;
> tree base_plus_step, bpsps;
> int cps, cpsps;
> + bool known_not_to_wrap;
>
> /* FIXME: The following code will not be used anymore once
> http://gcc.gnu.org/ml/gcc-patches/2005-06/msg02025.html is
> @@ -2077,8 +2078,10 @@ scev_probably_wraps_p (tree type, tree b
>
> estimate_numbers_of_iterations_loop (loop);
> for (bound = loop->bounds; bound; bound = bound->next)
> - if (proved_non_wrapping_p (at_stmt, bound, type, valid_niter))
> - return false;
> + if (!proved_non_wrapping_p (at_stmt, bound, type, valid_niter))
> + known_not_to_wrap = false;
> + if (known_not_to_wrap)
> + return false;
>
> /* At this point we still don't have a proof that the iv does not
> overflow: give up. */
>
known_to_wrap may be uninitialized at the if statement here.
You need to init it to true.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26304
