tree-vrp.c (register_new_assert_for): Simplify for backward walk.

2012-09-14  Richard Guenther  <rguenther@suse.de>

	* tree-vrp.c (register_new_assert_for): Simplify for backward
	walk.
	(find_assert_locations_1): Walk the basic-block backwards,
	properly add/prune from live.  Use live for asserts derived
	from stmts.

From-SVN: r191293

gcc/ChangeLog

+2012-09-14  Richard Guenther  <rguenther@suse.de>
+
+	* tree-vrp.c (register_new_assert_for): Simplify for backward
+	walk.
+	(find_assert_locations_1): Walk the basic-block backwards,
+	properly add/prune from live.  Use live for asserts derived
+	from stmts.
+
 2012-09-14  Marc Glisse  <marc.glisse@inria.fr>
 
 	* tree-ssa-forwprop.c (simplify_bitfield_ref): Call

gcc/tree-vrp.c

@@ -4384,24 +4384,7 @@ register_new_assert_for (tree name, tree expr,
 	  && (loc->expr == expr
 	      || operand_equal_p (loc->expr, expr, 0)))
 	{
-	  /* If the assertion NAME COMP_CODE VAL has already been
-	     registered at a basic block that dominates DEST_BB, then
-	     we don't need to insert the same assertion again.  Note
-	     that we don't check strict dominance here to avoid
-	     replicating the same assertion inside the same basic
-	     block more than once (e.g., when a pointer is
-	     dereferenced several times inside a block).
-
-	     An exception to this rule are edge insertions.  If the
-	     new assertion is to be inserted on edge E, then it will
-	     dominate all the other insertions that we may want to
-	     insert in DEST_BB.  So, if we are doing an edge
-	     insertion, don't do this dominance check.  */
-          if (e == NULL
-	      && dominated_by_p (CDI_DOMINATORS, dest_bb, loc->bb))
-	    return;
-
-	  /* Otherwise, if E is not a critical edge and DEST_BB
+	  /* If E is not a critical edge and DEST_BB
 	     dominates the existing location for the assertion, move
 	     the assertion up in the dominance tree by updating its
 	     location information.  */
@@ -5439,7 +5422,6 @@ find_assert_locations_1 (basic_block bb, sbitmap live)
 {
   gimple_stmt_iterator si;
   gimple last;
-  gimple phi;
   bool need_assert;
 
   need_assert = false;
@@ -5462,7 +5444,7 @@ find_assert_locations_1 (basic_block bb, sbitmap live)
 
   /* Traverse all the statements in BB marking used names and looking
      for statements that may infer assertions for their used operands.  */
-  for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si))
+  for (si = gsi_last_bb (bb); !gsi_end_p (si); gsi_prev (&si))
     {
       gimple stmt;
       tree op;
@@ -5479,8 +5461,10 @@ find_assert_locations_1 (basic_block bb, sbitmap live)
 	  tree value;
 	  enum tree_code comp_code;
 
-	  /* Mark OP in our live bitmap.  */
-	  SET_BIT (live, SSA_NAME_VERSION (op));
+	  /* If op is not live beyond this stmt, do not bother to insert
+	     asserts for it.  */
+	  if (!TEST_BIT (live, SSA_NAME_VERSION (op)))
+	    continue;
 
 	  /* If OP is used in such a way that we can infer a value
 	     range for it, and we don't find a previous assertion for
@@ -5520,25 +5504,28 @@ find_assert_locations_1 (basic_block bb, sbitmap live)
 		    }
 		}
 
-	      /* If OP is used only once, namely in this STMT, don't
-		 bother creating an ASSERT_EXPR for it.  Such an
-		 ASSERT_EXPR would do nothing but increase compile time.  */
-	      if (!has_single_use (op))
-		{
-		  register_new_assert_for (op, op, comp_code, value,
-					   bb, NULL, si);
-		  need_assert = true;
-		}
+	      register_new_assert_for (op, op, comp_code, value, bb, NULL, si);
+	      need_assert = true;
 	    }
 	}
+
+      /* Update live.  */
+      FOR_EACH_SSA_TREE_OPERAND (op, stmt, i, SSA_OP_USE)
+	SET_BIT (live, SSA_NAME_VERSION (op));
+      FOR_EACH_SSA_TREE_OPERAND (op, stmt, i, SSA_OP_DEF)
+	RESET_BIT (live, SSA_NAME_VERSION (op));
     }
 
-  /* Traverse all PHI nodes in BB marking used operands.  */
+  /* Traverse all PHI nodes in BB, updating live.  */
   for (si = gsi_start_phis (bb); !gsi_end_p(si); gsi_next (&si))
     {
       use_operand_p arg_p;
       ssa_op_iter i;
-      phi = gsi_stmt (si);
+      gimple phi = gsi_stmt (si);
+      tree res = gimple_phi_result (phi);
+
+      if (virtual_operand_p (res))
+	continue;
 
       FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_USE)
 	{
@@ -5546,6 +5533,8 @@ find_assert_locations_1 (basic_block bb, sbitmap live)
 	  if (TREE_CODE (arg) == SSA_NAME)
 	    SET_BIT (live, SSA_NAME_VERSION (arg));
 	}
+
+      RESET_BIT (live, SSA_NAME_VERSION (res));
     }
 
   return need_assert;