[PATCH] Fix compile-time hog in MPX boundary checking (PR target/84988).

[Martin Liška]

Hi.

This is a work-around to not iterate all members of array that can be huge.
As MPX will be removed in GCC 9.x, I hope it's acceptable. I don't want to come
up with a new param for it.

Survives tests&bootstrap on x86_64-linux-gnu.

Martin

gcc/ChangeLog:

2018-03-20  Martin Liska  <mli...@suse.cz>

        PR target/84988
        * tree-chkp.c (CHKP_ARRAY_MAX_CHECK_STEPS): Define a new macro.
        (chkp_find_bound_slots_1): Limit number of iterations.
---
 gcc/tree-chkp.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)



diff --git a/gcc/tree-chkp.c b/gcc/tree-chkp.c
index 40497ce94e7..d10e6c40423 100644
--- a/gcc/tree-chkp.c
+++ b/gcc/tree-chkp.c
@@ -1688,6 +1688,10 @@ chkp_find_bounds_for_elem (tree elem, tree *all_bounds,
     }
 }
 
+/* Maximum number of elements to check in an array.  */
+
+#define CHKP_ARRAY_MAX_CHECK_STEPS    4096
+
 /* Fill HAVE_BOUND output bitmap with information about
    bounds requred for object of type TYPE.
 
@@ -1733,7 +1737,9 @@ chkp_find_bound_slots_1 (const_tree type, bitmap have_bound,
 	  || integer_minus_onep (maxval))
 	return;
 
-      for (cur = 0; cur <= TREE_INT_CST_LOW (maxval); cur++)
+      for (cur = 0;
+	  cur <= MIN (CHKP_ARRAY_MAX_CHECK_STEPS, TREE_INT_CST_LOW (maxval));
+	  cur++)
 	chkp_find_bound_slots_1 (etype, have_bound, offs + cur * esize);
     }
 }