re PR tree-optimization/22236 (wrong code for casts and scev)

	PR tree-optimization/22236
	* tree-cfg.c (print_pred_bbs, print_succ_bbs): Correctly print
	successors and predecessors.
	* tree-chrec.c (chrec_convert): Before converting, check that
	sequences don't wrap.
	* tree-data-ref.c (compute_estimated_nb_iterations): Moved ...
	(analyze_array): Extern.
	(find_data_references_in_loop): Remove call to
	compute_estimated_nb_iterations.
	* tree-data-ref.h (analyze_array): Declared.
	* tree-flow-inline.h (single_ssa_tree_operand, single_ssa_use_operand,
	single_ssa_def_operand, zero_ssa_operands): Fix documentation.
	* tree-flow.h (scev_probably_wraps_p): Declare with an extra parameter.
	* tree-scalar-evolution.c (instantiate_parameters_1): Factor entry
	condition.
	* tree-ssa-loop-ivcanon.c: Fix documentation.
	* tree-ssa-loop-ivopts.c (idx_find_step): Add a fixme note.
	* tree-ssa-loop-niter.c (compute_estimated_nb_iterations): ... here.
	(infer_loop_bounds_from_undefined): New.
	(estimate_numbers_of_iterations_loop): Use
	infer_loop_bounds_from_undefined.
	(used_in_pointer_arithmetic_p): New.
	(scev_probably_wraps_p): Pass an extra parameter.  Call
	used_in_pointer_arithmetic_p.  Check that AT_STMT is not null.
	(convert_step): Fix documentation.
	* tree-vrp.c (adjust_range_with_scev): Call instantiate_parameters.
	Use initial_condition_in_loop_num and evolution_part_in_loop_num
	instead of CHREC_LEFT and CHREC_RIGHT.  Adjust the call to
	scev_probably_wraps_p.

From-SVN: r103055

1 files changed, 18 insertions, 3 deletions

diff --git a/gcc/tree-chrec.c b/gcc/tree-chrec.c
index b48813c..1a22922 100644
--- a/gcc/tree-chrec.c
+++ b/gcc/tree-chrec.c
@@ -1110,9 +1110,24 @@ chrec_convert (tree type, tree chrec, tree at_stmt)
 
   if (evolution_function_is_affine_p (chrec))
     {
-      tree step = convert_step (current_loops->parray[CHREC_VARIABLE (chrec)],
- 				type, CHREC_LEFT (chrec), CHREC_RIGHT (chrec),
- 				at_stmt);
+      tree step;
+      bool dummy;
+
+      /* Avoid conversion of (signed char) {(uchar)1, +, (uchar)1}_x
+	 when it is not possible to prove that the scev does not wrap.
+	 See PR22236, where a sequence 1, 2, ..., 255 has to be
+	 converted to signed char, but this would wrap: 
+	 1, 2, ..., 127, -128, ...  The result should not be
+	 {(schar)1, +, (schar)1}_x, but instead, we should keep the
+	 conversion: (schar) {(uchar)1, +, (uchar)1}_x.  */
+      if (scev_probably_wraps_p (type, CHREC_LEFT (chrec), CHREC_RIGHT (chrec),
+				 at_stmt,
+				 current_loops->parray[CHREC_VARIABLE (chrec)],
+				 &dummy, &dummy))
+	return fold_convert (type, chrec);
+
+      step = convert_step (current_loops->parray[CHREC_VARIABLE (chrec)], type,
+			   CHREC_LEFT (chrec), CHREC_RIGHT (chrec), at_stmt);
       if (!step)
  	return fold_convert (type, chrec);