re PR tree-optimization/61607 (DOM missed jump threading and destroyed loops)

2014-06-26  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/61607
	* tree-ssa-copy.c (copy_prop_visit_phi_node): Adjust comment
	explaining why we restrict copies on loop depth.
	* tree-ssa-dom.c (cprop_operand): Remove restriction on
	on loop depth.
	(record_equivalences_from_phis): Instead add it here.

	* gcc.dg/tree-ssa/ssa-dom-thread-5.c: New testcase.

From-SVN: r212026

gcc/ChangeLog

+2014-06-26  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/61607
+	* tree-ssa-copy.c (copy_prop_visit_phi_node): Adjust comment
+	explaining why we restrict copies on loop depth.
+	* tree-ssa-dom.c (cprop_operand): Remove restriction on
+	on loop depth.
+	(record_equivalences_from_phis): Instead add it here.
+
 2014-06-26  Bernd Schmidt  <bernds@codesourcery.com>
 
         * Makefile.in (COLLECT2_OBJS): Add collect-utils.o.

gcc/testsuite/ChangeLog

+2014-06-26  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/61607
+	* gcc.dg/tree-ssa/ssa-dom-thread-5.c: New testcase.
+
 2014-06-26  Vidya Praveen  <vidyapraveen@arm.com>
 
 	* gcc.dg/inline-22.c: Add bind_pic_locally.

gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-5.c

+/* { dg-do compile } */
+/* { dg-options "-Os -fno-tree-fre -fdump-tree-dom1-details" } */
+
+void foo(int *);
+void f2(int dst[3], int R)
+{
+  int i, inter[2];
+  _Bool inter0p = 0;
+  _Bool inter1p = 0;
+  for (i = 1; i < R; i++)
+    {
+      inter0p = 1;
+      inter1p = 1;
+    }
+  if (inter0p)
+    inter[0] = 1;
+  if (inter1p)
+    inter[1] = 1;
+  foo(inter);
+}
+
+/* { dg-final { scan-tree-dump "Threaded jump" "dom1" } } */
+/* { dg-final { cleanup-tree-dump "dom1" } } */

gcc/tree-ssa-copy.c

@@ -401,11 +401,8 @@ copy_prop_visit_phi_node (gimple phi)
 	arg_value = valueize_val (arg);
 
       /* Avoid copy propagation from an inner into an outer loop.
-	 Otherwise, this may move loop variant variables outside of
-	 their loops and prevent coalescing opportunities.  If the
-	 value was loop invariant, it will be hoisted by LICM and
-	 exposed for copy propagation.
-	 ???  The value will be always loop invariant.
+	 Otherwise, this may introduce uses of loop variant variables
+	 outside of their loops and prevent coalescing opportunities.
 	 In loop-closed SSA form do not copy-propagate through
 	 PHI nodes in blocks with a loop exit edge predecessor.  */
       if (TREE_CODE (arg_value) == SSA_NAME

gcc/tree-ssa-dom.c

@@ -1234,7 +1234,13 @@ record_equivalences_from_phis (basic_block bb)
 	 this, since this is a true assignment and not an equivalence
 	 inferred from a comparison.  All uses of this ssa name are dominated
 	 by this assignment, so unwinding just costs time and space.  */
-      if (i == gimple_phi_num_args (phi) && may_propagate_copy (lhs, rhs))
+      if (i == gimple_phi_num_args (phi)
+	  && may_propagate_copy (lhs, rhs)
+	  /* Do not propagate copies if the propagated value is at a deeper loop
+	     depth than the propagatee.  Otherwise, this may introduce uses
+	     of loop variant variables outside of their loops and prevent
+	     coalescing opportunities.  */
+	  && !(loop_depth_of_name (rhs) > loop_depth_of_name (lhs)))
 	set_ssa_name_value (lhs, rhs);
     }
 }
@@ -2247,14 +2253,6 @@ cprop_operand (gimple stmt, use_operand_p op_p)
       if (!may_propagate_copy (op, val))
 	return;
 
-      /* Do not propagate copies if the propagated value is at a deeper loop
-	 depth than the propagatee.  Otherwise, this may move loop variant
-	 variables outside of their loops and prevent coalescing
-	 opportunities.  If the value was loop invariant, it will be hoisted
-	 by LICM and exposed for copy propagation.  */
-      if (loop_depth_of_name (val) > loop_depth_of_name (op))
-	return;
-
       /* Do not propagate copies into simple IV increment statements.
          See PR23821 for how this can disturb IV analysis.  */
       if (TREE_CODE (val) != INTEGER_CST