re PR tree-optimization/30730 (-Wunsafe-loop-optimizations gives too many warnings)

PR tree-optimization/30730
	PR tree-optimization/26900
	* tree-ssa-loop-niter.c: Include gmp.h.
	(bounds): New type.
	(mpz_set_double_int, get_type_bounds, mpz_to_double_int,
	split_to_var_and_offset, determine_value_range,
	bound_difference_of_offsetted_base, refine_bounds_using_guard,
	bound_difference, bounds_add, bounds_negate,
	number_of_iterations_ne_max, dump_affine_iv): New functions.
	(number_of_iterations_ne, number_of_iterations_lt_to_ne,
	assert_loop_rolls_lt, assert_loop_rolls_le): Use bounds on the
	difference of initial and final value of control iv to validate
	results.
	(number_of_iterations_cond): Add loop parameter.  Determine bounds
	on the difference of the extremes of the control iv.  Add dumps.
	(expand_simple_operations): Handle phi nodes.
	(simplify_using_initial_conditions): Do not record used conditions.
	(number_of_iterations_exit): Pass loop to number_of_iterations_cond.
	Do not set additional_info.
	(implies_nonnegative_p, implies_ge_p): Removed.
	(derive_constant_upper_bound): Do not use parameter `additional'.
	(record_estimate): Parameter `additional' removed.  Parameter
	`i_bound' added.  Do not call derive_constant_upper_bound.
	(record_nonwrapping_iv): Use derive_constant_upper_bound to
	bound the number of iterations estimate.
	(estimate_numbers_of_iterations_loop): Pass the estimate from
	the number of iterations analysis to record_estimate.
	* tree.h (multiple_of_p): Declare.
	* tree-scalar-evolution.c (expression_expensive_p): Removed.
	(scev_const_prop): Do not check expression_expensive_p.
	* fold-const.c (multiple_of_p): Exported.
	* double-int.c (double_int_mask): Exported.
	* double-int.h (double_int_mask): Declare.
	* tree-flow.h (struct tree_niter_desc): Removed additional_info
	field.  Added max field.

	* gcc.dg/tree-ssa/loop-26.c: New test.

From-SVN: r122896

gcc/ChangeLog

@@ -1,3 +1,41 @@
+2007-03-13  Zdenek Dvorak  <dvorakz@suse.cz>
+
+	PR tree-optimization/30730
+	PR tree-optimization/26900
+	* tree-ssa-loop-niter.c: Include gmp.h.
+	(bounds): New type.
+	(mpz_set_double_int, get_type_bounds, mpz_to_double_int,
+	split_to_var_and_offset, determine_value_range,
+	bound_difference_of_offsetted_base, refine_bounds_using_guard,
+	bound_difference, bounds_add, bounds_negate,
+	number_of_iterations_ne_max, dump_affine_iv): New functions.
+	(number_of_iterations_ne, number_of_iterations_lt_to_ne,
+	assert_loop_rolls_lt, assert_loop_rolls_le): Use bounds on the
+	difference of initial and final value of control iv to validate
+	results.
+	(number_of_iterations_cond): Add loop parameter.  Determine bounds
+	on the difference of the extremes of the control iv.  Add dumps.
+	(expand_simple_operations): Handle phi nodes.
+	(simplify_using_initial_conditions): Do not record used conditions.
+	(number_of_iterations_exit): Pass loop to number_of_iterations_cond.
+	Do not set additional_info.
+	(implies_nonnegative_p, implies_ge_p): Removed.
+	(derive_constant_upper_bound): Do not use parameter `additional'.
+	(record_estimate): Parameter `additional' removed.  Parameter
+	`i_bound' added.  Do not call derive_constant_upper_bound.
+	(record_nonwrapping_iv): Use derive_constant_upper_bound to
+	bound the number of iterations estimate.
+	(estimate_numbers_of_iterations_loop): Pass the estimate from
+	the number of iterations analysis to record_estimate.
+	* tree.h (multiple_of_p): Declare.
+	* tree-scalar-evolution.c (expression_expensive_p): Removed.
+	(scev_const_prop): Do not check expression_expensive_p.
+	* fold-const.c (multiple_of_p): Exported.
+	* double-int.c (double_int_mask): Exported.
+	* double-int.h (double_int_mask): Declare.
+	* tree-flow.h (struct tree_niter_desc): Removed additional_info
+	field.  Added max field.
+
 2007-03-13  David Taylor  <taylor@candd.org>
 
 	PR driver/12448:

gcc/double-int.c

@@ -26,7 +26,7 @@ Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
 
 /* Returns mask for PREC bits.  */
 
-static inline double_int
+double_int
 double_int_mask (unsigned prec)
 {
   unsigned HOST_WIDE_INT m;

gcc/double-int.h

@@ -134,6 +134,7 @@ void dump_double_int (FILE *, double_int, bool);
 double_int double_int_ext (double_int, unsigned, bool);
 double_int double_int_sext (double_int, unsigned);
 double_int double_int_zext (double_int, unsigned);
+double_int double_int_mask (unsigned);
 
 #define ALL_ONES (~((unsigned HOST_WIDE_INT) 0))
 

gcc/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2007-03-13  Zdenek Dvorak  <dvorakz@suse.cz>
+
+	* gcc.dg/tree-ssa/loop-26.c: New test.
+
 2007-03-13  Uros Bizjak  <ubizjak@gmail.com>
 	
 	* testsuite/gcc.target/i386/cmpxchg16b-1.c: New test.
@@ -10,13 +14,13 @@
 
 2007-03-12  Seongbae Park <seongbae.park@gmail.com>
 
- 	* gcc.dg/wvla-1.c: New test
- 	* gcc.dg/wvla-2.c: New test
- 	* gcc.dg/wvla-3.c: New test
- 	* gcc.dg/wvla-4.c: New test
- 	* gcc.dg/wvla-5.c: New test
- 	* gcc.dg/wvla-6.c: New test
- 	* gcc.dg/wvla-7.c: New test
+	* gcc.dg/wvla-1.c: New test
+	* gcc.dg/wvla-2.c: New test
+	* gcc.dg/wvla-3.c: New test
+	* gcc.dg/wvla-4.c: New test
+	* gcc.dg/wvla-5.c: New test
+	* gcc.dg/wvla-6.c: New test
+	* gcc.dg/wvla-7.c: New test
 	* g++.dg/warn/Wvla-1.C: New test
 	* g++.dg/warn/Wvla-2.C: New test
 	* g++.dg/warn/Wvla-3.C: New test

gcc/testsuite/gcc.dg/tree-ssa/loop-26.c

@@ -0,0 +1,29 @@
+/* PR 30730, PR 26900, number of iterations analysis should be able to
+   determine number of iterations of the following loops unconditionally.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O -fstrict-overflow -fdump-tree-empty" } */
+
+unsigned foo(unsigned int n)
+{
+  unsigned x = 0;;
+
+  while (n > 10)
+    {
+      n -= 2;
+      x++;
+    }
+
+  return x;
+}
+
+int foo0(int i0, int i1)
+{
+  int i, j = 0;
+  for (i=i0; i<=i1+1; ++i)
+    ++j;
+  return j;
+}
+
+/* { dg-final { scan-tree-dump-times "Removing empty loop" 2 "empty" } } */
+/* { dg-final { cleanup-tree-dump "empty" } } */

gcc/tree-flow.h

@@ -822,18 +822,8 @@ struct tree_niter_desc
 			   a loop (provided that assumptions == true and
 			   may_be_zero == false), more precisely the number
 			   of executions of the latch of the loop.  */
-  tree additional_info;	/* The boolean expression.  Sometimes we use additional
-			   knowledge to simplify the other expressions
-			   contained in this structure (for example the
-			   knowledge about value ranges of operands on entry to
-			   the loop).  If this is a case, conjunction of such
-			   condition is stored in this field, so that we do not
-			   lose the information: for example if may_be_zero
-			   is (n <= 0) and niter is (unsigned) n, we know
-			   that the number of iterations is at most
-			   MAX_SIGNED_INT.  However if the (n <= 0) assumption
-			   is eliminated (by looking at the guard on entry of
-			   the loop), then the information would be lost.  */
+  double_int max;	/* The upper bound on the number of iterations of
+			   the loop.  */
 
   /* The simplified shape of the exit condition.  The loop exits if
      CONTROL CMP BOUND is false, where CMP is one of NE_EXPR,

gcc/tree-scalar-evolution.c

@@ -2864,14 +2864,6 @@ scev_finalize (void)
   BITMAP_FREE (already_instantiated);
 }
 
-/* Returns true if EXPR looks expensive.  */
-
-static bool
-expression_expensive_p (tree expr)
-{
-  return force_expr_to_var_cost (expr) >= target_spill_cost;
-}
-
 /* Replace ssa names for that scev can prove they are constant by the
    appropriate constants.  Also perform final value replacement in loops,
    in case the replacement expressions are cheap.
@@ -2958,10 +2950,13 @@ scev_const_prop (void)
 	continue;
 
       niter = number_of_latch_executions (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))
+      /* We used to check here whether the computation of NITER is expensive,
+	 and avoided final value elimination if that is the case.  The problem
+	 is that it is hard to evaluate whether the expression is too
+	 expensive, as we do not know what optimization opportunities the
+	 the elimination of the final value may reveal.  Therefore, we now
+	 eliminate the final values of induction variables unconditionally.  */
+      if (niter == chrec_dont_know)
 	continue;
 
       /* Ensure that it is possible to insert new statements somewhere.  */

gcc/tree.h

@@ -4481,6 +4481,7 @@ extern enum tree_code invert_tree_comparison (enum tree_code, bool);
 
 extern bool tree_expr_nonzero_p (tree);
 extern bool tree_expr_nonzero_warnv_p (tree, bool *);
+extern int multiple_of_p (tree, tree, tree);
 
 /* In builtins.c */
 extern tree fold_call_expr (tree, bool);