re PR tree-optimization/18527 (cannot determine number of iterations for loops with <=)

	PR tree-optimization/18527
	* tree-ssa-loop-niter.c (number_of_iterations_cond,
	number_of_iterations_special, number_of_iterations_exit):
	Move base and step of an iv to a single structure.  Add
	no_overflow flag, and use it in # of iterations analysis.
	* tree-scalar-evolution.c (analyze_scalar_evolution_in_loop): Add
	folded_casts argument.
	(simple_iv): Pass base and step in a structure.  Set no_overflow
	flag.
	(scev_const_prop): Add argument to analyze_scalar_evolution_in_loop.
	Evaluate expensiveness of computing # of iterations instead of
	the final expression.
	* tree-scalar-evolution.h (affine_iv): New structure.
	(simple_iv): Declaration changed.
	* tree-chrec.c (chrec_apply): Handle chrecs containing symbols.
	* tree-ssa-loop-ivopts.c (determine_biv_step, find_givs_in_stmt_scev,
	find_givs_in_stmt): Changed due to simple_iv change.

	* gcc.dg/tree-ssa/loop-15.c: New test.

From-SVN: r109427

gcc/ChangeLog

+2005-01-06  Zdenek Dvorak <dvorakz@suse.cz>
+
+	PR tree-optimization/18527
+	* tree-ssa-loop-niter.c (number_of_iterations_cond,
+	number_of_iterations_special, number_of_iterations_exit):
+	Move base and step of an iv to a single structure.  Add
+	no_overflow flag, and use it in # of iterations analysis.
+	* tree-scalar-evolution.c (analyze_scalar_evolution_in_loop): Add
+	folded_casts argument.
+	(simple_iv): Pass base and step in a structure.  Set no_overflow
+	flag.
+	(scev_const_prop): Add argument to analyze_scalar_evolution_in_loop.
+	Evaluate expensiveness of computing # of iterations instead of
+	the final expression.
+	* tree-scalar-evolution.h (affine_iv): New structure.
+	(simple_iv): Declaration changed.
+	* tree-chrec.c (chrec_apply): Handle chrecs containing symbols.
+	* tree-ssa-loop-ivopts.c (determine_biv_step, find_givs_in_stmt_scev,
+	find_givs_in_stmt): Changed due to simple_iv change.
+
 2005-01-06  Jeff Law  <law@redhat.com>
 
 	PR ada/24994

gcc/testsuite/ChangeLog

+2005-01-06  Zdenek Dvorak <dvorakz@suse.cz>
+
+	* gcc.dg/tree-ssa/loop-15.c: New test.
+
 2005-01-05  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
 
 	PR fortran/25598

gcc/testsuite/gcc.dg/tree-ssa/loop-15.c

+/* A test for # of iterations analysis (signed counter cannot wrap) and final
+   value replacement.  */
+
+/* { dg-options "-O2 -fdump-tree-vars" } */
+
+int foo(void);
+
+int bla(void)
+{
+  int i, n = foo (), j;
+
+  j = 0;
+  /* The loop should be removed completely.  */
+  for (i = 1; i <= n; i++)
+    j += n;
+
+  /* Should be replaced with return n * n;  */
+  return j;
+}
+
+/* Since the loop is removed, there should be no addition.  */
+/* { dg-final { scan-tree-dump-times "\\+" 0 "vars" } } */
+/* { dg-final { scan-tree-dump-times "n \\* n" 1 "vars" } } */
+
+/* The if from the loop header copying remains in the code.  */
+/* { dg-final { scan-tree-dump-times "if " 1 "vars" } } */
+/* { dg-final { cleanup-tree-dump "vars" } } */

gcc/tree-chrec.c

@@ -533,10 +533,9 @@ chrec_apply (unsigned var,
       /* When the symbols are defined in an outer loop, it is possible
 	 to symbolically compute the apply, since the symbols are
 	 constants with respect to the varying loop.  */
-      || chrec_contains_symbols_defined_in_loop (chrec, var)
-      || chrec_contains_symbols (x))
+      || chrec_contains_symbols_defined_in_loop (chrec, var))
     return chrec_dont_know;
-  
+ 
   if (dump_file && (dump_flags & TDF_DETAILS))
     fprintf (dump_file, "(chrec_apply \n");
 
@@ -546,14 +545,10 @@ chrec_apply (unsigned var,
   if (evolution_function_is_affine_p (chrec))
     {
       /* "{a, +, b} (x)"  ->  "a + b*x".  */
-      if (TREE_CODE (CHREC_LEFT (chrec)) == INTEGER_CST
-	  && integer_zerop (CHREC_LEFT (chrec)))
-	res = chrec_fold_multiply (type, CHREC_RIGHT (chrec), x);
-      
-      else
-	res = chrec_fold_plus (type, CHREC_LEFT (chrec), 
-			       chrec_fold_multiply (type, 
-						    CHREC_RIGHT (chrec), x));
+      x = chrec_convert (type, x, NULL_TREE);
+      res = chrec_fold_multiply (type, CHREC_RIGHT (chrec), x);
+      if (!integer_zerop (CHREC_LEFT (chrec)))
+	res = chrec_fold_plus (type, CHREC_LEFT (chrec), res);
     }
   
   else if (TREE_CODE (chrec) != POLYNOMIAL_CHREC)
@@ -563,7 +558,6 @@ chrec_apply (unsigned var,
 	   && tree_int_cst_sgn (x) == 1)
     /* testsuite/.../ssa-chrec-38.c.  */
     res = chrec_evaluate (var, chrec, x, 0);
-
   else
     res = chrec_dont_know;
   

gcc/tree-scalar-evolution.c

@@ -1831,19 +1831,28 @@ analyze_scalar_evolution (struct loop *loop, tree var)
 
 /* Analyze scalar evolution of use of VERSION in USE_LOOP with respect to
    WRTO_LOOP (which should be a superloop of both USE_LOOP and definition
-   of VERSION).  */
+   of VERSION).
+
+   FOLDED_CASTS is set to true if resolve_mixers used
+   chrec_convert_aggressive (TODO -- not really, we are way too conservative
+   at the moment in order to keep things simple).  */
 
 static tree
 analyze_scalar_evolution_in_loop (struct loop *wrto_loop, struct loop *use_loop,
-				  tree version)
+				  tree version, bool *folded_casts)
 {
   bool val = false;
-  tree ev = version;
+  tree ev = version, tmp;
 
+  if (folded_casts)
+    *folded_casts = false;
   while (1)
     {
-      ev = analyze_scalar_evolution (use_loop, ev);
-      ev = resolve_mixers (use_loop, ev);
+      tmp = analyze_scalar_evolution (use_loop, ev);
+      ev = resolve_mixers (use_loop, tmp);
+
+      if (folded_casts && tmp != ev)
+	*folded_casts = true;
 
       if (use_loop == wrto_loop)
 	return ev;
@@ -2561,33 +2570,38 @@ scev_reset (void)
 }
 
 /* Checks whether OP behaves as a simple affine iv of LOOP in STMT and returns
-   its BASE and STEP if possible.  If ALLOW_NONCONSTANT_STEP is true, we
-   want STEP to be invariant in LOOP.  Otherwise we require it to be an
-   integer constant.  */
+   its base and step in IV if possible.  If ALLOW_NONCONSTANT_STEP is true, we
+   want step to be invariant in LOOP.  Otherwise we require it to be an
+   integer constant.  IV->no_overflow is set to true if we are sure the iv cannot
+   overflow (e.g.  because it is computed in signed arithmetics).  */
 
 bool
-simple_iv (struct loop *loop, tree stmt, tree op, tree *base, tree *step,
+simple_iv (struct loop *loop, tree stmt, tree op, affine_iv *iv,
 	   bool allow_nonconstant_step)
 {
   basic_block bb = bb_for_stmt (stmt);
   tree type, ev;
+  bool folded_casts;
 
-  *base = NULL_TREE;
-  *step = NULL_TREE;
+  iv->base = NULL_TREE;
+  iv->step = NULL_TREE;
+  iv->no_overflow = false;
 
   type = TREE_TYPE (op);
   if (TREE_CODE (type) != INTEGER_TYPE
       && TREE_CODE (type) != POINTER_TYPE)
     return false;
 
-  ev = analyze_scalar_evolution_in_loop (loop, bb->loop_father, op);
+  ev = analyze_scalar_evolution_in_loop (loop, bb->loop_father, op,
+					 &folded_casts);
   if (chrec_contains_undetermined (ev))
     return false;
 
   if (tree_does_not_contain_chrecs (ev)
       && !chrec_contains_symbols_defined_in_loop (ev, loop->num))
     {
-      *base = ev;
+      iv->base = ev;
+      iv->no_overflow = true;
       return true;
     }
 
@@ -2595,21 +2609,24 @@ simple_iv (struct loop *loop, tree stmt, tree op, tree *base, tree *step,
       || CHREC_VARIABLE (ev) != (unsigned) loop->num)
     return false;
 
-  *step = CHREC_RIGHT (ev);
+  iv->step = CHREC_RIGHT (ev);
   if (allow_nonconstant_step)
     {
-      if (tree_contains_chrecs (*step, NULL)
-	  || chrec_contains_symbols_defined_in_loop (*step, loop->num))
+      if (tree_contains_chrecs (iv->step, NULL)
+	  || chrec_contains_symbols_defined_in_loop (iv->step, loop->num))
 	return false;
     }
-  else if (TREE_CODE (*step) != INTEGER_CST)
+  else if (TREE_CODE (iv->step) != INTEGER_CST)
     return false;
 
-  *base = CHREC_LEFT (ev);
-  if (tree_contains_chrecs (*base, NULL)
-      || chrec_contains_symbols_defined_in_loop (*base, loop->num))
+  iv->base = CHREC_LEFT (ev);
+  if (tree_contains_chrecs (iv->base, NULL)
+      || chrec_contains_symbols_defined_in_loop (iv->base, loop->num))
     return false;
 
+  iv->no_overflow = (!folded_casts
+		     && !flag_wrapv
+		     && !TYPE_UNSIGNED (type));
   return true;
 }
 
@@ -2722,7 +2739,7 @@ scev_const_prop (void)
   for (i = current_loops->num - 1; i > 0; i--)
     {
       edge exit;
-      tree def, rslt, ass;
+      tree def, rslt, ass, niter;
       block_stmt_iterator bsi;
 
       loop = current_loops->parray[i];
@@ -2732,8 +2749,14 @@ scev_const_prop (void)
       /* If we do not know exact number of iterations of the loop, we cannot
 	 replace the final value.  */
       exit = loop->single_exit;
-      if (!exit
-	  || number_of_iterations_in_loop (loop) == chrec_dont_know)
+      if (!exit)
+	continue;
+
+      niter = number_of_iterations_in_loop (loop);
+      if (niter == chrec_dont_know
+	  /* If computing the number of iterations is expensive, it may be
+	     better not to introduce computations involving it.  */
+	  || expression_expensive_p (niter))
 	continue;
 
       /* Ensure that it is possible to insert new statements somewhere.  */
@@ -2756,17 +2779,12 @@ scev_const_prop (void)
 	      && !INTEGRAL_TYPE_P (TREE_TYPE (def)))
 	    continue;
 
-	  def = analyze_scalar_evolution_in_loop (ex_loop, loop, def);
+	  def = analyze_scalar_evolution_in_loop (ex_loop, loop, def, NULL);
 	  def = compute_overall_effect_of_inner_loop (ex_loop, def);
 	  if (!tree_does_not_contain_chrecs (def)
 	      || chrec_contains_symbols_defined_in_loop (def, ex_loop->num))
 	    continue;
 
-	  /* If computing the expression is expensive, let it remain in the
-	     loop.  */
-	  if (expression_expensive_p (def))
-	    continue;
-
 	  /* Eliminate the phi node and replace it by a computation outside
 	     the loop.  */
 	  def = unshare_expr (def);

gcc/tree-scalar-evolution.h

@@ -32,7 +32,19 @@ extern tree analyze_scalar_evolution (struct loop *, tree);
 extern tree instantiate_parameters (struct loop *, tree);
 extern void gather_stats_on_scev_database (void);
 extern void scev_analysis (void);
-extern bool simple_iv (struct loop *, tree, tree, tree *, tree *, bool);
 void scev_const_prop (void);
 
+/* Affine iv.  */
+
+typedef struct
+{
+  /* Iv = BASE + STEP * i.  */
+  tree base, step;
+
+  /* True if this iv does not overflow.  */
+  bool no_overflow;
+} affine_iv;
+
+extern bool simple_iv (struct loop *, tree, tree, affine_iv *, bool);
+
 #endif  /* GCC_TREE_SCALAR_EVOLUTION_H  */

gcc/tree-ssa-loop-ivopts.c

@@ -881,18 +881,16 @@ static tree
 determine_biv_step (tree phi)
 {
   struct loop *loop = bb_for_stmt (phi)->loop_father;
-  tree name = PHI_RESULT (phi), base, step;
+  tree name = PHI_RESULT (phi);
+  affine_iv iv;
 
   if (!is_gimple_reg (name))
     return NULL_TREE;
 
-  if (!simple_iv (loop, phi, name, &base, &step, true))
+  if (!simple_iv (loop, phi, name, &iv, true))
     return NULL_TREE;
 
-  if (zero_p (step))
-    return NULL_TREE;
-
-  return step;
+  return (zero_p (iv.step) ? NULL_TREE : iv.step);
 }
 
 /* Returns true if EXP is a ssa name that occurs in an abnormal phi node.  */
@@ -1044,17 +1042,16 @@ mark_bivs (struct ivopts_data *data)
 }
 
 /* Checks whether STMT defines a linear induction variable and stores its
-   parameters to BASE and STEP.  */
+   parameters to IV.  */
 
 static bool
-find_givs_in_stmt_scev (struct ivopts_data *data, tree stmt,
-			tree *base, tree *step)
+find_givs_in_stmt_scev (struct ivopts_data *data, tree stmt, affine_iv *iv)
 {
   tree lhs;
   struct loop *loop = data->current_loop;
 
-  *base = NULL_TREE;
-  *step = NULL_TREE;
+  iv->base = NULL_TREE;
+  iv->step = NULL_TREE;
 
   if (TREE_CODE (stmt) != MODIFY_EXPR)
     return false;
@@ -1063,12 +1060,12 @@ find_givs_in_stmt_scev (struct ivopts_data *data, tree stmt,
   if (TREE_CODE (lhs) != SSA_NAME)
     return false;
 
-  if (!simple_iv (loop, stmt, TREE_OPERAND (stmt, 1), base, step, true))
+  if (!simple_iv (loop, stmt, TREE_OPERAND (stmt, 1), iv, true))
     return false;
-  *base = expand_simple_operations (*base);
+  iv->base = expand_simple_operations (iv->base);
 
-  if (contains_abnormal_ssa_name_p (*base)
-      || contains_abnormal_ssa_name_p (*step))
+  if (contains_abnormal_ssa_name_p (iv->base)
+      || contains_abnormal_ssa_name_p (iv->step))
     return false;
 
   return true;
@@ -1079,12 +1076,12 @@ find_givs_in_stmt_scev (struct ivopts_data *data, tree stmt,
 static void
 find_givs_in_stmt (struct ivopts_data *data, tree stmt)
 {
-  tree base, step;
+  affine_iv iv;
 
-  if (!find_givs_in_stmt_scev (data, stmt, &base, &step))
+  if (!find_givs_in_stmt_scev (data, stmt, &iv))
     return;
 
-  set_iv (data, TREE_OPERAND (stmt, 0), base, step);
+  set_iv (data, TREE_OPERAND (stmt, 0), iv.base, iv.step);
 }
 
 /* Finds general ivs in basic block BB.  */