Index: gcc/gimple-ssa-strength-reduction.c
===================================================================
--- gcc/gimple-ssa-strength-reduction.c	(revision 250791)
+++ gcc/gimple-ssa-strength-reduction.c	(working copy)
@@ -2074,6 +2074,15 @@ replace_mult_candidate (slsr_cand_t c, tree basis_
 {
   tree target_type = TREE_TYPE (gimple_assign_lhs (c->cand_stmt));
   enum tree_code cand_code = gimple_assign_rhs_code (c->cand_stmt);
+  unsigned int prec = (POINTER_TYPE_P (target_type)
+		       ? TYPE_PRECISION (sizetype)
+		       : TYPE_PRECISION (target_type));
+  tree maxval = (POINTER_TYPE_P (target_type)
+		 ? TYPE_MAX_VALUE (sizetype)
+		 : TYPE_MAX_VALUE (target_type));
+  /*
+  wide_int maxval = wi::max_value (prec, sgn);
+  */
 
   /* It is highly unlikely, but possible, that the resulting
      bump doesn't fit in a HWI.  Abandon the replacement
@@ -2082,6 +2091,20 @@ replace_mult_candidate (slsr_cand_t c, tree basis_
      types but allows for safe negation without twisted logic.  */
   if (wi::fits_shwi_p (bump)
       && bump.to_shwi () != HOST_WIDE_INT_MIN
+      /* It is more likely that the bump doesn't fit in the target
+	 type, so check whether constraining it to that type changes
+	 the value.  For a signed type, the value mustn't change.
+         For an unsigned type, the value may only change to a 
+         congruent value (for negative bumps).  */
+      && (TYPE_UNSIGNED (target_type)
+	  || wi::eq_p (bump, wi::ext (bump, prec, SIGNED)))
+      && (!TYPE_UNSIGNED (target_type)
+	  || wi::eq_p (bump, wi::ext (bump, prec, UNSIGNED))
+	  || wi::eq_p (bump + wi::to_widest (maxval) + 1,
+		       wi::ext (bump, prec, UNSIGNED)))
+	  /*
+	  || wi::eq_p (bump + maxval + 1, wi::ext (bump, prec, UNSIGNED)))
+	  */
       /* It is not useful to replace casts, copies, negates, or adds of
 	 an SSA name and a constant.  */
       && cand_code != SSA_NAME