[Bug tree-optimization/26304] [4.2 Regression] 25_algorithms/prev_permutation/1.cc on powerpc{64,}-linux and powerpc-darwin

[pinskia at gcc dot gnu dot org]

------- 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.  */



----------------------------

Makes it work,  Now I am not going to say this is the "correct" fix or not.  
What I am going to say, this is the most logical fix in that we know one iv can
not overflow does not mean all will not.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |spop at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26304