Introduce a param-switch-limit for EVRP.

Very large switches cause a lot of range calculations with multiple subranges
to happen.  This can cause quadratic or even exponetial time increases in
large testcases.  This patch introduces a param variable to limit
the size of switches EVRP will process.

	* gimple-range-edge.cc (gimple_outgoing_range::gimple_outgoing_range):
	Add parameter to limit size when recognizing switches.
	(gimple_outgoing_range::edge_range_p): Check size limit.
	* gimple-range-edge.h (gimple_outgoing_range): Add size field.
	* gimple-range-gori.cc (gori_map::calculate_gori): Ignore switches
	that exceed the size limit.
	(gori_compute::gori_compute): Add initializer.
	* params.opt (evrp-switch-limit): New.
	* doc/invoke.texi: Update docs.

1 files changed, 6 insertions, 1 deletions

diff --git a/gcc/gimple-range-edge.cc b/gcc/gimple-range-edge.cc
index d11153e..afffc8d 100644
--- a/gcc/gimple-range-edge.cc
+++ b/gcc/gimple-range-edge.cc
@@ -65,9 +65,10 @@ gcond_edge_range (irange &r, edge e)
 }
 
 
-gimple_outgoing_range::gimple_outgoing_range ()
+gimple_outgoing_range::gimple_outgoing_range (int max_sw_edges)
 {
   m_edge_table = NULL;
+  m_max_edges = max_sw_edges;
 }
 
 
@@ -192,6 +193,10 @@ gimple_outgoing_range::edge_range_p (irange &r, edge e)
       return s;
     }
 
+  // Only process switches if it within the size limit.
+  if (EDGE_COUNT (e->src->succs) > (unsigned)m_max_edges)
+    return NULL;
+
   gcc_checking_assert (is_a<gswitch *> (s));
   gswitch *sw = as_a<gswitch *> (s);
   tree type = TREE_TYPE (gimple_switch_index (sw));