re PR tree-optimization/18316 (Missed IV optimization)

	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.

From-SVN: r99059

gcc/ChangeLog

+2005-05-01  Zdenek Dvorak  <dvorakz@suse.cz>
+
+	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.
+
 2005-04-30  Michael Matz  <matz@suse.de>
 
 	* config/i386/i386.md (movmemsi): Also active when

gcc/testsuite/ChangeLog

+2005-05-01  Zdenek Dvorak  <dvorakz@suse.cz>
+
+	* gcc.dg/tree-ssa/loop-8.c: New test.
+
 2005-04-30  Michael Maty  <matz@suse.de>
 
 	* gcc.dg/inline-mcpy.c: New test.

gcc/testsuite/gcc.dg/tree-ssa/loop-8.c

+/* A test for strength reduction of ivs with nonconstant step.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-vars" } */
+
+int bar (void);
+
+int a[100];
+
+void xxx (void)
+{
+  int iter, step = bar ();
+
+  for (iter = 0; iter < 10; iter++)
+    a[iter * step] = bar ();
+}
+
+/* The array access should be strength reduced.  But to determine the value of
+   the step, we need to calculate step * sizeof (int), thus we need to be
+   a bit careful about which multiplications we disallow.  */
+
+/* { dg-final { scan-tree-dump-times "step \\* \[^0-9\]" 0 "vars" } } */
+/* { dg-final { scan-tree-dump-times "\[^0-9\] \\* step" 0 "vars" } } */
+
+/* { dg-final { cleanup-tree-dump "vars" } } */

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))

gcc/tree-scalar-evolution.h

@@ -32,6 +32,6 @@ 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 *);
+extern bool simple_iv (struct loop *, tree, tree, tree *, tree *, bool);
 
 #endif  /* GCC_TREE_SCALAR_EVOLUTION_H  */

gcc/tree-ssa-loop-manip.c

@@ -54,6 +54,7 @@ create_iv (tree base, tree step, tree var, struct loop *loop,
   tree stmt, initial, step1, stmts;
   tree vb, va;
   enum tree_code incr_op = PLUS_EXPR;
+  edge pe = loop_preheader_edge (loop);
 
   if (!var)
     {
@@ -92,6 +93,12 @@ create_iv (tree base, tree step, tree var, struct loop *loop,
 	}
     }
 
+  /* Gimplify the step if necessary.  We put the computations in front of the
+     loop (i.e. the step should be loop invariant).  */
+  step = force_gimple_operand (step, &stmts, true, var);
+  if (stmts)
+    bsi_insert_on_edge_immediate_loop (pe, stmts);
+
   stmt = build2 (MODIFY_EXPR, void_type_node, va,
 		 build2 (incr_op, TREE_TYPE (base),
 			 vb, step));
@@ -103,11 +110,7 @@ create_iv (tree base, tree step, tree var, struct loop *loop,
 
   initial = force_gimple_operand (base, &stmts, true, var);
   if (stmts)
-    {
-      edge pe = loop_preheader_edge (loop);
-
-      bsi_insert_on_edge_immediate_loop (pe, stmts);
-    }
+    bsi_insert_on_edge_immediate_loop (pe, stmts);
 
   stmt = create_phi_node (vb, loop->header);
   SSA_NAME_DEF_STMT (vb) = stmt;

gcc/tree-ssa-loop-niter.c

@@ -952,9 +952,9 @@ number_of_iterations_exit (struct loop *loop, edge exit,
       && !POINTER_TYPE_P (type))
     return false;
      
-  if (!simple_iv (loop, stmt, op0, &base0, &step0))
+  if (!simple_iv (loop, stmt, op0, &base0, &step0, false))
     return false;
-  if (!simple_iv (loop, stmt, op1, &base1, &step1))
+  if (!simple_iv (loop, stmt, op1, &base1, &step1, false))
     return false;
 
   niter->niter = NULL_TREE;

gcc/tree.c

@@ -518,7 +518,7 @@ tree
 build_int_cst_type (tree type, HOST_WIDE_INT low)
 {
   unsigned HOST_WIDE_INT val = (unsigned HOST_WIDE_INT) low;
-  unsigned HOST_WIDE_INT hi;
+  unsigned HOST_WIDE_INT hi, mask;
   unsigned bits;
   bool signed_p;
   bool negative;
@@ -538,10 +538,12 @@ build_int_cst_type (tree type, HOST_WIDE_INT low)
       negative = ((val >> (bits - 1)) & 1) != 0;
 
       /* Mask out the bits outside of the precision of the constant.  */
+      mask = (((unsigned HOST_WIDE_INT) 2) << (bits - 1)) - 1;
+
       if (signed_p && negative)
-	val = val | ((~(unsigned HOST_WIDE_INT) 0) << bits);
+	val |= ~mask;
       else
-	val = val & ~((~(unsigned HOST_WIDE_INT) 0) << bits);
+	val &= mask;
     }
 
   /* Determine the high bits.  */
@@ -556,7 +558,8 @@ build_int_cst_type (tree type, HOST_WIDE_INT low)
       else
 	{
 	  bits -= HOST_BITS_PER_WIDE_INT;
-	  hi = hi & ~((~(unsigned HOST_WIDE_INT) 0) << bits);
+	  mask = (((unsigned HOST_WIDE_INT) 2) << (bits - 1)) - 1;
+	  hi &= mask;
 	}
     }