re PR tree-optimization/68619 (error: loop with header 6 not in loop tree)

2015-12-10  Jeff Law  <law@redhat.com>

	PR tree-optimization/68619
	* tree-ssa-dom.c (dom_opt_dom_walker::before_dom_children): Propgate
	return value from optimize_stmt.
	(dom_opt_dom_walker): Add new argument to dom_walker constructor.
	(pass_dominator:execute): If a block has an unreachable edge,
	remove all jump threads through any successor of the affected block.
	(record_equivalences_from_phis): Ignore alternative if the edge
	does not have EDGE_EXECUTABLE set.
	(single_incoming_edge_ignoring_loop_edges): Similarly.
	(optimize_stmt): If a gimple_code has a compile-time constant
	condition, return the edge taken for that constant value.  Also
	change the condition to true/false as necessary.
	* domwalk.h (dom_walker::dom_walker): Add new argument
	skip_unreachable_blocks.  Don't provide empty constructor body.
	(dom_walker::before_dom_children): Change return type.
	(dom_walker::bb_reachable): Declare new private method.
	(dom_walker::propagate_unreachable_to_edges): Likewise.
	(dom_walker::m_unreachable_dom): Declare new private data member.
	(dom_walker::m_skip_unreachable_blocks): Likewise.
	* domwalk.c: Include dumpfile.h.
	(dom_walker::dom_walker): New constructor.  Initialize private data
	members.  If needed, set EDGE_EXECUTABLE for all edges in the CFG,
	extracted from tree-ssa-sccvn.c.
	(dom_walker::bb_reachable): New method extracted from tree-ssa-sccvn.c
	(dom_walker::propagate_unreachable_to_edges): Likewise.
	(dom_walker::walk): Only call before_dom_children on reachable
	blocks.  If before_dom_children returns an edge, then clear
	EDGE_EXECUTABLE for all other outgoing edges from the same block.
	For unreachable blocks, call propagate_unreachable_to_edges.
	Similarly, only call after_dom_children on reachable blocks.  For
	unreachable blocks, conditionally clear m_unreachable_dom.
	* tree-ssa-sccvn.c (sccvn_dom_walker::unreachable_dom): Remove
	private data member.
	(sccvn_dom_walker::after_dom_children): Use methods from dom_walker
	class.
	(run_scc_vn): Likewise.
	(sccvn_dom_walker::before_dom_children): Likewise.  Return the taken
	outgoing edge if a COND, SWITCH, or GOTO are optimized.
	* compare-elim.c (find_comparison_dom_walker::before_dom_children):
	Change return type to an edge.  Always return NULL.
	* fwprop.c (single_def_use_dom_walker::before_dom_children): Likewise.
	* gimple-ssa-strength-reduction.c
	(find_candidates_dom_walker::before_dom_children): Likewise.
	* ipa-prop.c (analysis_dom_walker::before_dom_children): Likewise.
	(ipcp_modif_dom_walker::before_dom_children): Likewise.
	* tree-into-ssa.c (rewrite_dom_walker::before_dom_children): Likewise.
	(rewrite_update_dom_walker::before_dom_children): Likewise.
	(mark_def_dom_children::before_dom_children): Likewise.
	* tree-ssa-dse.c (dse_dom_walker::before_dom_children): Likewise.
	* tree-ssa-loop-im.c
	(invariantness_dom_walker::before_dom_children): Likewise.
	(move_computations_dom_walker::before_dom_walker): Likewise.
	* tree-ssa-phiopt.c
	(nontrapping_dom_walker::before_dom_children): Likewise.
	* tree-ssa-pre.c
	(eliminate_dom_walker::before_dom_children): Likewise.
	* tree-ssa-propagate.c
	(substitute_and_fold_dom_walker::before_dom_children): Likewise.
	* tree-ssa-strlen.c
	(strlen_dom_walker::before_dom_children): Likewise.
	* tree-ssa-uncprop.c
	(uncprop_dom_walker::before_dom_children): Likewise.

	PR tree-optimization/68619
	* gcc.dg/tree-ssa/pr68619-1.c: New test.
	* gcc.dg/tree-ssa/pr68619-2.c: New test.
	* gcc.dg/tree-ssa/pr68619-3.c: New test.
	* gcc.dg/tree-ssa/pr68619-4.c: New test.
	* gcc.dg/tree-ssa/pr68619-5.c: New test.

From-SVN: r231527

1 files changed, 28 insertions, 3 deletions

diff --git a/gcc/domwalk.h b/gcc/domwalk.h
index 71a7c47..e631a67 100644
--- a/gcc/domwalk.h
+++ b/gcc/domwalk.h
@@ -30,13 +30,26 @@ along with GCC; see the file COPYING3.  If not see
 class dom_walker
 {
 public:
-  dom_walker (cdi_direction direction) : m_dom_direction (direction) {}
+  /* Use SKIP_UNREACHBLE_BLOCKS = true when your client can discover
+     that some edges are not executable.
+
+     If a client can discover that a COND, SWITCH or GOTO has a static
+     target in the before_dom_children callback, the taken edge should
+     be returned.  The generic walker will clear EDGE_EXECUTABLE on all
+     edges it can determine are not executable.  */
+  dom_walker (cdi_direction direction, bool skip_unreachable_blocks = false);
 
   /* Walk the dominator tree.  */
   void walk (basic_block);
 
-  /* Function to call before the recursive walk of the dominator children.  */
-  virtual void before_dom_children (basic_block) {}
+  /* Function to call before the recursive walk of the dominator children.
+
+     Return value is the always taken edge if the block has multiple outgoing
+     edges, NULL otherwise.  When skipping unreachable blocks, the walker
+     uses the taken edge information to clear EDGE_EXECUTABLE on the other
+     edges, exposing unreachable blocks.  A NULL return value means all
+     outgoing edges should still be considered executable.  */
+  virtual edge before_dom_children (basic_block) { return NULL; }
 
   /* Function to call after the recursive walk of the dominator children.  */
   virtual void after_dom_children (basic_block) {}
@@ -47,6 +60,18 @@ private:
      if it is set to CDI_POST_DOMINATORS, then we walk the post
      dominator tree.  */
   const ENUM_BITFIELD (cdi_direction) m_dom_direction : 2;
+  bool m_skip_unreachable_blocks;
+  basic_block m_unreachable_dom;
+
+  /* Query whether or not the given block is reachable or not.  */
+  bool bb_reachable (struct function *, basic_block);
+
+  /* Given an unreachable block, propagate that property to outgoing
+     and possibly incoming edges for the block.  Typically called after
+     determining a block is unreachable in the before_dom_children
+     callback.  */
+  void propagate_unreachable_to_edges (basic_block, FILE *, int);
+
 };
 
 #endif