tree-ssa-loop-niter.c (tree_simplify_using_condition_1): New parameter.

	* tree-ssa-loop-niter.c (tree_simplify_using_condition_1): New
	parameter.
	(tree_simplify_using_condition): Ditto.
	(simplify_using_initial_conditions): Ditto.
	(loop_exits_before_overflow): Pass new argument to function
	simplify_using_initial_conditions.  Remove case for type conversions
	simplification.
	* tree-ssa-loop-niter.h (simplify_using_initial_conditions): New
	parameter.
	* tree-scalar-evolution.c (simple_iv): Simplify type conversions
	in iv base using loop initial conditions.

	gcc/testsuite/ChangeLog
	* gcc.dg/tree-ssa/loop-bound-2.c: New test.
	* gcc.dg/tree-ssa/loop-bound-4.c: New test.
	* gcc.dg/tree-ssa/loop-bound-6.c: New test.

From-SVN: r227843

gcc/ChangeLog

+2015-09-17  Bin Cheng  <bin.cheng@arm.com>
+
+	* tree-ssa-loop-niter.c (tree_simplify_using_condition_1): New
+	parameter.
+	(tree_simplify_using_condition): Ditto.
+	(simplify_using_initial_conditions): Ditto.
+	(loop_exits_before_overflow): Pass new argument to function
+	simplify_using_initial_conditions.  Remove case for type conversions
+	simplification.
+	* tree-ssa-loop-niter.h (simplify_using_initial_conditions): New
+	parameter.
+	* tree-scalar-evolution.c (simple_iv): Simplify type conversions
+	in iv base using loop initial conditions.
+
 2015-09-16  Jeff Law  <law@redhat.com>
 
 	PR tree-optimization/47679

gcc/testsuite/ChangeLog

+2015-09-17  Bin Cheng  <bin.cheng@arm.com>
+
+	* gcc.dg/tree-ssa/loop-bound-2.c: New test.
+	* gcc.dg/tree-ssa/loop-bound-4.c: New test.
+	* gcc.dg/tree-ssa/loop-bound-6.c: New test.
+
 2015-09-16  John Marino  <gnugcc@marino.st>
 
 	* gfortran.dg/read_dir.f90: XFAIL this testcase on DragonFly.

gcc/testsuite/gcc.dg/tree-ssa/loop-bound-2.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-ivopts-details" } */
+
+int *a;
+
+int
+foo (signed char s, signed char l)
+{
+  signed char i;
+  int sum = 0;
+
+  for (i = s; i < l; i++)
+    {
+      sum += a[i];
+    }
+
+  return sum;
+}
+
+/* Check loop niter bound information.  */
+/* { dg-final { scan-tree-dump "bounded by 254" "ivopts" } } */
+/* { dg-final { scan-tree-dump-not "bounded by 255" "ivopts" } } */
+/* { dg-final { scan-tree-dump-not "zero if " "ivopts" } } */

gcc/testsuite/gcc.dg/tree-ssa/loop-bound-4.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-ivopts-details" } */
+
+int *a;
+
+int
+foo (signed char s, signed char l)
+{
+  signed char i;
+  int sum = 0;
+
+  for (i = s; i > l; i--)
+    {
+      sum += a[i];
+    }
+
+  return sum;
+}
+
+/* Check loop niter bound information.  */
+/* { dg-final { scan-tree-dump "bounded by 254" "ivopts" } } */
+/* { dg-final { scan-tree-dump-not "bounded by 255" "ivopts" } } */
+/* { dg-final { scan-tree-dump-not "zero if " "ivopts" } } */

gcc/testsuite/gcc.dg/tree-ssa/loop-bound-6.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-ivopts-details" } */
+
+int *a;
+
+int
+foo (signed char s)
+{
+  signed char i;
+  int sum = 0;
+
+  for (i = s; i > 0; i--)
+    {
+      sum += a[i];
+    }
+
+  return sum;
+}
+
+/* Check loop niter bound information.  */
+/* { dg-final { scan-tree-dump "bounded by 126" "ivopts" } } */
+/* { dg-final { scan-tree-dump-not "bounded by 127" "ivopts" } } */
+/* { dg-final { scan-tree-dump-not "zero if " "ivopts" } } */

gcc/tree-scalar-evolution.c

@@ -3234,8 +3234,10 @@ bool
 simple_iv (struct loop *wrto_loop, struct loop *use_loop, tree op,
 	   affine_iv *iv, bool allow_nonconstant_step)
 {
-  tree type, ev;
-  bool folded_casts;
+  enum tree_code code;
+  tree type, ev, base, e, stop;
+  wide_int extreme;
+  bool folded_casts, overflow;
 
   iv->base = NULL_TREE;
   iv->step = NULL_TREE;
@@ -3276,6 +3278,82 @@ simple_iv (struct loop *wrto_loop, struct loop *use_loop, tree op,
   iv->no_overflow = (!folded_casts && ANY_INTEGRAL_TYPE_P (type)
 		     && TYPE_OVERFLOW_UNDEFINED (type));
 
+  /* Try to simplify iv base:
+
+       (signed T) ((unsigned T)base + step) ;; TREE_TYPE (base) == signed T
+	 == (signed T)(unsigned T)base + step
+	 == base + step
+
+     If we can prove operation (base + step) doesn't overflow or underflow.
+     Specifically, we try to prove below conditions are satisfied:
+
+	     base <= UPPER_BOUND (type) - step  ;;step > 0
+	     base >= LOWER_BOUND (type) - step  ;;step < 0
+
+     This is done by proving the reverse conditions are false using loop's
+     initial conditions.
+
+     The is necessary to make loop niter, or iv overflow analysis easier
+     for below example:
+
+       int foo (int *a, signed char s, signed char l)
+	 {
+	   signed char i;
+	   for (i = s; i < l; i++)
+	     a[i] = 0;
+	   return 0;
+	  }
+
+     Note variable I is firstly converted to type unsigned char, incremented,
+     then converted back to type signed char.  */
+
+  if (wrto_loop->num != use_loop->num)
+    return true;
+
+  if (!CONVERT_EXPR_P (iv->base) || TREE_CODE (iv->step) != INTEGER_CST)
+    return true;
+
+  type = TREE_TYPE (iv->base);
+  e = TREE_OPERAND (iv->base, 0);
+  if (TREE_CODE (e) != PLUS_EXPR
+      || TREE_CODE (TREE_OPERAND (e, 1)) != INTEGER_CST
+      || !tree_int_cst_equal (iv->step,
+			      fold_convert (type, TREE_OPERAND (e, 1))))
+    return true;
+  e = TREE_OPERAND (e, 0);
+  if (!CONVERT_EXPR_P (e))
+    return true;
+  base = TREE_OPERAND (e, 0);
+  if (!useless_type_conversion_p (type, TREE_TYPE (base)))
+    return true;
+
+  if (tree_int_cst_sign_bit (iv->step))
+    {
+      code = LT_EXPR;
+      extreme = wi::min_value (type);
+    }
+  else
+    {
+      code = GT_EXPR;
+      extreme = wi::max_value (type);
+    }
+  overflow = false;
+  extreme = wi::sub (extreme, iv->step, TYPE_SIGN (type), &overflow);
+  if (overflow)
+    return true;
+  e = fold_build2 (code, boolean_type_node, base,
+		   wide_int_to_tree (type, extreme));
+  stop = (TREE_CODE (base) == SSA_NAME) ? base : NULL;
+  e = simplify_using_initial_conditions (use_loop, e, stop);
+  if (!integer_zerop (e))
+    return true;
+
+  if (POINTER_TYPE_P (TREE_TYPE (base)))
+    code = POINTER_PLUS_EXPR;
+  else
+    code = PLUS_EXPR;
+
+  iv->base = fold_build2 (code, TREE_TYPE (base), base, iv->step);
   return true;
 }
 

gcc/tree-ssa-loop-niter.c

@@ -1926,7 +1926,7 @@ expand_simple_operations (tree expr, tree stop)
    expression (or EXPR unchanged, if no simplification was possible).  */
 
 static tree
-tree_simplify_using_condition_1 (tree cond, tree expr)
+tree_simplify_using_condition_1 (tree cond, tree expr, tree stop)
 {
   bool changed;
   tree e, te, e0, e1, e2, notcond;
@@ -1941,17 +1941,17 @@ tree_simplify_using_condition_1 (tree cond, tree expr)
     {
       changed = false;
 
-      e0 = tree_simplify_using_condition_1 (cond, TREE_OPERAND (expr, 0));
+      e0 = tree_simplify_using_condition_1 (cond, TREE_OPERAND (expr, 0), stop);
       if (TREE_OPERAND (expr, 0) != e0)
 	changed = true;
 
-      e1 = tree_simplify_using_condition_1 (cond, TREE_OPERAND (expr, 1));
+      e1 = tree_simplify_using_condition_1 (cond, TREE_OPERAND (expr, 1), stop);
       if (TREE_OPERAND (expr, 1) != e1)
 	changed = true;
 
       if (code == COND_EXPR)
 	{
-	  e2 = tree_simplify_using_condition_1 (cond, TREE_OPERAND (expr, 2));
+	  e2 = tree_simplify_using_condition_1 (cond, TREE_OPERAND (expr, 2), stop);
 	  if (TREE_OPERAND (expr, 2) != e2)
 	    changed = true;
 	}
@@ -2014,7 +2014,7 @@ tree_simplify_using_condition_1 (tree cond, tree expr)
 	return boolean_true_node;
     }
 
-  te = expand_simple_operations (expr);
+  te = expand_simple_operations (expr, stop);
 
   /* Check whether COND ==> EXPR.  */
   notcond = invert_truthvalue (cond);
@@ -2038,19 +2038,19 @@ tree_simplify_using_condition_1 (tree cond, tree expr)
    the loop do not cause us to fail.  */
 
 static tree
-tree_simplify_using_condition (tree cond, tree expr)
+tree_simplify_using_condition (tree cond, tree expr, tree stop)
 {
-  cond = expand_simple_operations (cond);
+  cond = expand_simple_operations (cond, stop);
 
-  return tree_simplify_using_condition_1 (cond, expr);
+  return tree_simplify_using_condition_1 (cond, expr, stop);
 }
 
 /* Tries to simplify EXPR using the conditions on entry to LOOP.
    Returns the simplified expression (or EXPR unchanged, if no
-   simplification was possible).*/
+   simplification was possible).  */
 
-static tree
-simplify_using_initial_conditions (struct loop *loop, tree expr)
+tree
+simplify_using_initial_conditions (struct loop *loop, tree expr, tree stop)
 {
   edge e;
   basic_block bb;
@@ -2082,7 +2082,7 @@ simplify_using_initial_conditions (struct loop *loop, tree expr)
 			  gimple_cond_rhs (stmt));
       if (e->flags & EDGE_FALSE_VALUE)
 	cond = invert_truthvalue (cond);
-      expr = tree_simplify_using_condition (cond, expr);
+      expr = tree_simplify_using_condition (cond, expr, stop);
       /* Break if EXPR is simplified to const values.  */
       if (expr && (integer_zerop (expr) || integer_nonzerop (expr)))
 	break;
@@ -4114,137 +4114,68 @@ loop_exits_before_overflow (tree base, tree step,
      help of analyzed loop control IV.  This is done only for IVs with
      constant step because otherwise we don't have the information.  */
   if (TREE_CODE (step) == INTEGER_CST)
-    for (civ = loop->control_ivs; civ; civ = civ->next)
-      {
-	enum tree_code code;
-	tree stepped, extreme, civ_type = TREE_TYPE (civ->step);
-
-	/* Have to consider type difference because operand_equal_p ignores
-	   that for constants.  */
-	if (TYPE_UNSIGNED (type) != TYPE_UNSIGNED (civ_type)
-	    || element_precision (type) != element_precision (civ_type))
-	  continue;
-
-	/* Only consider control IV with same step.  */
-	if (!operand_equal_p (step, civ->step, 0))
-	  continue;
-
-	/* Done proving if this is a no-overflow control IV.  */
-	if (operand_equal_p (base, civ->base, 0))
-	  return true;
-
-	/* If this is a before stepping control IV, in other words, we have
-
-	     {civ_base, step} = {base + step, step}
-
-	   Because civ {base + step, step} doesn't overflow during loop
-	   iterations, {base, step} will not overflow if we can prove the
-	   operation "base + step" does not overflow.  Specifically, we try
-	   to prove below conditions are satisfied:
-
-	     base <= UPPER_BOUND (type) - step  ;;step > 0
-	     base >= LOWER_BOUND (type) - step  ;;step < 0
-
-	   by proving the reverse conditions are false using loop's initial
-	   condition.  */
-	if (POINTER_TYPE_P (TREE_TYPE (base)))
-	  code = POINTER_PLUS_EXPR;
-	else
-	  code = PLUS_EXPR;
+    {
+      tree stop = (TREE_CODE (base) == SSA_NAME) ? base : NULL;
 
-	stepped = fold_build2 (code, TREE_TYPE (base), base, step);
-	if (operand_equal_p (stepped, civ->base, 0))
-	  {
-	    if (tree_int_cst_sign_bit (step))
-	      {
-		code = LT_EXPR;
-		extreme = lower_bound_in_type (type, type);
-	      }
-	    else
-	      {
-		code = GT_EXPR;
-		extreme = upper_bound_in_type (type, type);
-	      }
-	    extreme = fold_build2 (MINUS_EXPR, type, extreme, step);
-	    e = fold_build2 (code, boolean_type_node, base, extreme);
-	    e = simplify_using_initial_conditions (loop, e);
-	    if (integer_zerop (e))
-	      return true;
+      for (civ = loop->control_ivs; civ; civ = civ->next)
+	{
+	  enum tree_code code;
+	  tree stepped, extreme, civ_type = TREE_TYPE (civ->step);
 
+	  /* Have to consider type difference because operand_equal_p ignores
+	     that for constants.  */
+	  if (TYPE_UNSIGNED (type) != TYPE_UNSIGNED (civ_type)
+	      || element_precision (type) != element_precision (civ_type))
 	    continue;
-	  }
-
-	/* Similar to above, only in this case we have:
-
-	     {civ_base, step} = {(signed T)((unsigned T)base + step), step}
-	     && TREE_TYPE (civ_base) = signed T.
-
-	   We prove that below condition is satisfied:
-
-	     (signed T)((unsigned T)base + step)
-	       == (signed T)(unsigned T)base + step
-	       == base + step
 
-	   because of exact the same reason as above.  This also proves
-	   there is no overflow in the operation "base + step", thus the
-	   induction variable {base, step} during loop iterations.
+	  /* Only consider control IV with same step.  */
+	  if (!operand_equal_p (step, civ->step, 0))
+	    continue;
 
-	   This is necessary to handle cases as below:
+	  /* Done proving if this is a no-overflow control IV.  */
+	  if (operand_equal_p (base, civ->base, 0))
+	    return true;
 
-	     int foo (int *a, signed char s, signed char l)
-	       {
-		 signed char i;
-		 for (i = s; i < l; i++)
-		   a[i] = 0;
-		 return 0;
-	       }
+	  /* If this is a before stepping control IV, in other words, we have
 
-	   The variable I is firstly converted to type unsigned char,
-	   incremented, then converted back to type signed char.  */
-	if (!CONVERT_EXPR_P (civ->base) || TREE_TYPE (civ->base) != type)
-	  continue;
-	e = TREE_OPERAND (civ->base, 0);
-	if (TREE_CODE (e) != PLUS_EXPR
-	    || TREE_CODE (TREE_OPERAND (e, 1)) != INTEGER_CST
-	    || !operand_equal_p (step,
-				 fold_convert (type,
-					       TREE_OPERAND (e, 1)), 0))
-	  continue;
-	e = TREE_OPERAND (e, 0);
-	if (!CONVERT_EXPR_P (e) || !operand_equal_p (e, unsigned_base, 0))
-	  continue;
-	e = TREE_OPERAND (e, 0);
-	/* It may still be possible to prove no overflow even if condition
-	   "operand_equal_p (e, base, 0)" isn't satisfied here, like below
-	   example:
+	       {civ_base, step} = {base + step, step}
 
-	     e             : ssa_var                 ; unsigned long type
-	     base          : (int) ssa_var
-	     unsigned_base : (unsigned int) ssa_var
+	     Because civ {base + step, step} doesn't overflow during loop
+	     iterations, {base, step} will not overflow if we can prove the
+	     operation "base + step" does not overflow.  Specifically, we try
+	     to prove below conditions are satisfied:
 
-	   Unfortunately this is a rare case observed during GCC profiled
-	   bootstrap.  See PR66638 for more information.
+	       base <= UPPER_BOUND (type) - step  ;;step > 0
+	       base >= LOWER_BOUND (type) - step  ;;step < 0
 
-	   For now, we just skip the possibility.  */
-	if (!operand_equal_p (e, base, 0))
-	  continue;
+	     by proving the reverse conditions are false using loop's initial
+	     condition.  */
+	  if (POINTER_TYPE_P (TREE_TYPE (base)))
+	    code = POINTER_PLUS_EXPR;
+	  else
+	    code = PLUS_EXPR;
 
-	if (tree_int_cst_sign_bit (step))
-	  {
-	    code = LT_EXPR;
-	    extreme = lower_bound_in_type (type, type);
-	  }
-	else
-	  {
-	    code = GT_EXPR;
-	    extreme = upper_bound_in_type (type, type);
-	  }
-	extreme = fold_build2 (MINUS_EXPR, type, extreme, step);
-	e = fold_build2 (code, boolean_type_node, base, extreme);
-	e = simplify_using_initial_conditions (loop, e);
-	if (integer_zerop (e))
-	  return true;
-      }
+	  stepped = fold_build2 (code, TREE_TYPE (base), base, step);
+	  if (operand_equal_p (stepped, civ->base, 0))
+	    {
+	      if (tree_int_cst_sign_bit (step))
+		{
+		  code = LT_EXPR;
+		  extreme = lower_bound_in_type (type, type);
+		}
+	      else
+		{
+		  code = GT_EXPR;
+		  extreme = upper_bound_in_type (type, type);
+		}
+	      extreme = fold_build2 (MINUS_EXPR, type, extreme, step);
+	      e = fold_build2 (code, boolean_type_node, base, extreme);
+	      e = simplify_using_initial_conditions (loop, e, stop);
+	      if (integer_zerop (e))
+		return true;
+	    }
+        }
+    }
 
   return false;
 }

gcc/tree-ssa-loop-niter.h

@@ -21,6 +21,8 @@ along with GCC; see the file COPYING3.  If not see
 #define GCC_TREE_SSA_LOOP_NITER_H
 
 extern tree expand_simple_operations (tree, tree = NULL);
+extern tree simplify_using_initial_conditions (struct loop *,
+					       tree, tree = NULL);
 extern bool loop_only_exit_p (const struct loop *, const_edge);
 extern bool number_of_iterations_exit (struct loop *, edge,
 				       struct tree_niter_desc *niter, bool,