The previous solution for PR77916 was inadequately tested, for which I
sincerely apologize.  I've reinstated the stopgap fix previously
reverted, as follows.

Thanks for your patience,

2016-10-18  Bill Schmidt  <wschm...@linux.vnet.ibm.com>

        PR tree-optimization/77916
        * gimple-ssa-strength-reduction.c (analyze_increments): Reinstate
        stopgap fix, as pointers with -1 increment are still broken.

Index: gcc/gimple-ssa-strength-reduction.c
--- gcc/gimple-ssa-strength-reduction.c (revision 241302)
+++ gcc/gimple-ssa-strength-reduction.c (working copy)
@@ -2825,6 +2825,10 @@ analyze_increments (slsr_cand_t first_dep, machine
                   && !POINTER_TYPE_P (first_dep->cand_type)))
        incr_vec[i].cost = COST_NEUTRAL;
+      /* FIXME: Still having trouble with pointers with a -1 increment.  */
+      else if (incr == -1 && POINTER_TYPE_P (first_dep->cand_type))
+       incr_vec[i].cost = COST_INFINITE;
       /* FORNOW: If we need to add an initializer, give up if a cast from
         the candidate's type to its stride's type can lose precision.
         This could eventually be handled better by expressly retaining the

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