PR tree-optimization/18316

	PR tree-optimization/19126
	* tree.c (build_int_cst_type): Avoid shift by size of type.
	* tree-scalar-evolution.c (simple_iv): Add allow_nonconstant_step
	argument.
	* tree-scalar-evolution.h (simple_iv): Declaration changed.
	* tree-ssa-loop-ivopts.c (struct iv_cand): Add depends_on
	field.
	(dump_cand): Dump depends_on information.
	(determine_biv_step): Add argument to simple_iv call.
	(contains_abnormal_ssa_name_p): Handle case expr == NULL.
	(find_bivs, find_givs_in_stmt_scev): Do not require step to be a
	constant.
	(add_candidate_1): Record depends_on for candidates.
	(tree_int_cst_sign_bit, constant_multiple_of): New functions.
	(get_computation_at, get_computation_cost_at, may_eliminate_iv):
	Handle ivs with nonconstant step.
	(iv_ca_set_remove_invariants, iv_ca_set_add_invariants): New functions.
	(iv_ca_set_no_cp, iv_ca_set_cp): Handle cand->depends_on.
	(create_new_iv): Unshare the step before passing it to create_iv.
	(free_loop_data): Free cand->depends_on.
	(build_addr_strip_iref): New function.
	(find_interesting_uses_address): Use build_addr_strip_iref.
	(strip_offset_1): Split the recursive part from strip_offset.
	Strip constant offset component_refs and array_refs.
	(strip_offset): Split the recursive part to strip_offset_1.
	(add_address_candidates): Removed.
	(add_derived_ivs_candidates): Do not use add_address_candidates.
	(add_iv_value_candidates): Add candidates with stripped constant
	offset.  Consider all candidates with initial value 0 important.
	(struct affine_tree_combination): New.
	(aff_combination_const, aff_combination_elt, aff_combination_scale,
	aff_combination_add_elt, aff_combination_add,
	tree_to_aff_combination, add_elt_to_tree, aff_combination_to_tree,
	fold_affine_sum): New functions.
	(get_computation_at): Use fold_affine_sum.
	* tree-ssa-loop-manip.c (create_iv): Handle ivs with nonconstant step.
	* tree-ssa-loop-niter.c (number_of_iterations_exit): Add argument
	to simple_iv call.

	* gcc.dg/tree-ssa/loop-8.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@99059 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 13 insertions, 3 deletions

diff --git a/gcc/tree-scalar-evolution.c b/gcc/tree-scalar-evolution.c
index ca808934efa..c923409d6ed 100644
--- a/gcc/tree-scalar-evolution.c
+++ b/gcc/tree-scalar-evolution.c
@@ -2547,10 +2547,13 @@ scev_reset (void)
 }
 
 /* Checks whether OP behaves as a simple affine iv of LOOP in STMT and returns
-   its BASE and STEP if possible.  */
+   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.  */
 
 bool
-simple_iv (struct loop *loop, tree stmt, tree op, tree *base, tree *step)
+simple_iv (struct loop *loop, tree stmt, tree op, tree *base, tree *step,
+	   bool allow_nonconstant_step)
 {
   basic_block bb = bb_for_stmt (stmt);
   tree type, ev;
@@ -2579,8 +2582,15 @@ simple_iv (struct loop *loop, tree stmt, tree op, tree *base, tree *step)
     return false;
 
   *step = CHREC_RIGHT (ev);
-  if (TREE_CODE (*step) != INTEGER_CST)
+  if (allow_nonconstant_step)
+    {
+      if (tree_contains_chrecs (*step, NULL)
+	  || chrec_contains_symbols_defined_in_loop (*step, loop->num))
+	return false;
+    }
+  else if (TREE_CODE (*step) != INTEGER_CST)
     return false;
+
   *base = CHREC_LEFT (ev);
   if (tree_contains_chrecs (*base, NULL)
       || chrec_contains_symbols_defined_in_loop (*base, loop->num))