common.opt (fkeep-gc-roots-live): New undocumented option.

gcc/:
	* common.opt (fkeep-gc-roots-live): New undocumented option.
	* tree-ssa-loop-ivopts.c (add_candidate_1): If
	-fkeep-gc-roots-live, skip pointers.
	(add_iv_candidate_for_biv): Handle add_candidate_1 returning
	NULL.

gcc/testsuite/:
	* gcc.dg/tree-ssa/ivopt_5.c: New test.

From-SVN: r232888

1 files changed, 15 insertions, 2 deletions

diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c
index 3faed93..4026d28 100644
--- a/gcc/tree-ssa-loop-ivopts.c
+++ b/gcc/tree-ssa-loop-ivopts.c
@@ -2815,6 +2815,16 @@ add_candidate_1 (struct ivopts_data *data,
   struct iv_cand *cand = NULL;
   tree type, orig_type;
 
+  /* -fkeep-gc-roots-live means that we have to keep a real pointer
+     live, but the ivopts code may replace a real pointer with one
+     pointing before or after the memory block that is then adjusted
+     into the memory block during the loop.  FIXME: It would likely be
+     better to actually force the pointer live and still use ivopts;
+     for example, it would be enough to write the pointer into memory
+     and keep it there until after the loop.  */
+  if (flag_keep_gc_roots_live && POINTER_TYPE_P (TREE_TYPE (base)))
+    return NULL;
+
   /* For non-original variables, make sure their values are computed in a type
      that does not invoke undefined behavior on overflows (since in general,
      we cannot prove that these induction variables are non-wrapping).  */
@@ -3083,8 +3093,11 @@ add_iv_candidate_for_biv (struct ivopts_data *data, struct iv *iv)
 	  cand = add_candidate_1 (data,
 				  iv->base, iv->step, true, IP_ORIGINAL, NULL,
 				  SSA_NAME_DEF_STMT (def));
-	  cand->var_before = iv->ssa_name;
-	  cand->var_after = def;
+	  if (cand)
+	    {
+	      cand->var_before = iv->ssa_name;
+	      cand->var_after = def;
+	    }
 	}
       else
 	gcc_assert (gimple_bb (phi) == data->current_loop->header);