Transform switch_conversion into a class.

2018-06-20  Martin Liska  <mliska@suse.cz>

	* tree-switch-conversion.c (MAX_CASE_BIT_TESTS): Remove.
	(hoist_edge_and_branch_if_true): Likewise.
	(expand_switch_using_bit_tests_p): Likewise.
	(struct case_bit_test): Likewise.
	(case_bit_test_cmp): Likewise.
	(emit_case_bit_tests): Likewise.
	(switch_conversion::switch_conversion): New class.
	(struct switch_conv_info): Remove old struct.
	(collect_switch_conv_info): More to ...
	(switch_conversion::collect): ... this.
	(check_range): Likewise.
	(switch_conversion::check_range): Likewise.
	(check_all_empty_except_final): Likewise.
	(switch_conversion::check_all_empty_except_final): Likewise.
	(check_final_bb): Likewise.
	(switch_conversion::check_final_bb): Likewise.
	(create_temp_arrays): Likewise.
	(switch_conversion::create_temp_arrays): Likewise.
	(free_temp_arrays): Likewise.
	(gather_default_values): Likewise.
	(switch_conversion::gather_default_values): Likewise.
	(build_constructors): Likewise.
	(switch_conversion::build_constructors): Likewise.
	(constructor_contains_same_values_p): Likewise.
	(switch_conversion::contains_same_values_p): Likewise.
	(array_value_type): Likewise.
	(switch_conversion::array_value_type): Likewise.
	(build_one_array): Likewise.
	(switch_conversion::build_one_array): Likewise.
	(build_arrays): Likewise.
	(switch_conversion::build_arrays): Likewise.
	(gen_def_assigns): Likewise.
	(switch_conversion::gen_def_assigns): Likewise.
	(prune_bbs): Likewise.
	(switch_conversion::prune_bbs): Likewise.
	(fix_phi_nodes): Likewise.
	(switch_conversion::fix_phi_nodes): Likewise.
	(gen_inbound_check): Likewise.
	(switch_conversion::gen_inbound_check): Likewise.
	(process_switch): Use the newly created class.
	(switch_conversion::expand): New.
	(switch_conversion::~switch_conversion): New.
	* tree-switch-conversion.h: New file.

From-SVN: r261792

gcc/ChangeLog

+2018-06-20  Martin Liska  <mliska@suse.cz>
+
+	* tree-switch-conversion.c (MAX_CASE_BIT_TESTS): Remove.
+	(hoist_edge_and_branch_if_true): Likewise.
+	(expand_switch_using_bit_tests_p): Likewise.
+	(struct case_bit_test): Likewise.
+	(case_bit_test_cmp): Likewise.
+	(emit_case_bit_tests): Likewise.
+	(switch_conversion::switch_conversion): New class.
+	(struct switch_conv_info): Remove old struct.
+	(collect_switch_conv_info): More to ...
+	(switch_conversion::collect): ... this.
+	(check_range): Likewise.
+	(switch_conversion::check_range): Likewise.
+	(check_all_empty_except_final): Likewise.
+	(switch_conversion::check_all_empty_except_final): Likewise.
+	(check_final_bb): Likewise.
+	(switch_conversion::check_final_bb): Likewise.
+	(create_temp_arrays): Likewise.
+	(switch_conversion::create_temp_arrays): Likewise.
+	(free_temp_arrays): Likewise.
+	(gather_default_values): Likewise.
+	(switch_conversion::gather_default_values): Likewise.
+	(build_constructors): Likewise.
+	(switch_conversion::build_constructors): Likewise.
+	(constructor_contains_same_values_p): Likewise.
+	(switch_conversion::contains_same_values_p): Likewise.
+	(array_value_type): Likewise.
+	(switch_conversion::array_value_type): Likewise.
+	(build_one_array): Likewise.
+	(switch_conversion::build_one_array): Likewise.
+	(build_arrays): Likewise.
+	(switch_conversion::build_arrays): Likewise.
+	(gen_def_assigns): Likewise.
+	(switch_conversion::gen_def_assigns): Likewise.
+	(prune_bbs): Likewise.
+	(switch_conversion::prune_bbs): Likewise.
+	(fix_phi_nodes): Likewise.
+	(switch_conversion::fix_phi_nodes): Likewise.
+	(gen_inbound_check): Likewise.
+	(switch_conversion::gen_inbound_check): Likewise.
+	(process_switch): Use the newly created class.
+	(switch_conversion::expand): New.
+	(switch_conversion::~switch_conversion): New.
+	* tree-switch-conversion.h: New file.
+
 2018-06-20  Richard Sandiford  <richard.sandiford@arm.com>
 
 	* tree-vectorizer.h (NUM_PATTERNS, vect_recog_func_ptr): Move to

gcc/tree-switch-conversion.h

+/* Tree switch conversion for GNU compiler.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef TREE_SWITCH_CONVERSION_H
+#define TREE_SWITCH_CONVERSION_H
+
+namespace tree_switch_conversion {
+
+/*
+     Switch initialization conversion
+
+The following pass changes simple initializations of scalars in a switch
+statement into initializations from a static array.  Obviously, the values
+must be constant and known at compile time and a default branch must be
+provided.  For example, the following code:
+
+	int a,b;
+
+	switch (argc)
+	{
+	 case 1:
+	 case 2:
+		a_1 = 8;
+		b_1 = 6;
+		break;
+	 case 3:
+		a_2 = 9;
+		b_2 = 5;
+		break;
+	 case 12:
+		a_3 = 10;
+		b_3 = 4;
+		break;
+	 default:
+		a_4 = 16;
+		b_4 = 1;
+		break;
+	}
+	a_5 = PHI <a_1, a_2, a_3, a_4>
+	b_5 = PHI <b_1, b_2, b_3, b_4>
+
+
+is changed into:
+
+	static const int = CSWTCH01[] = {6, 6, 5, 1, 1, 1, 1, 1, 1, 1, 1, 4};
+	static const int = CSWTCH02[] = {8, 8, 9, 16, 16, 16, 16, 16, 16, 16,
+				 16, 16, 10};
+
+	if (((unsigned) argc) - 1 < 11)
+	  {
+	    a_6 = CSWTCH02[argc - 1];
+	    b_6 = CSWTCH01[argc - 1];
+	  }
+	else
+	  {
+	    a_7 = 16;
+	    b_7 = 1;
+	  }
+	a_5 = PHI <a_6, a_7>
+	b_b = PHI <b_6, b_7>
+
+There are further constraints.  Specifically, the range of values across all
+case labels must not be bigger than SWITCH_CONVERSION_BRANCH_RATIO (default
+eight) times the number of the actual switch branches.
+
+This transformation was contributed by Martin Jambor, see this e-mail:
+   http://gcc.gnu.org/ml/gcc-patches/2008-07/msg00011.html  */
+
+/* The main structure of the pass.  */
+struct switch_conversion
+{
+  /* Constructor.  */
+  switch_conversion ();
+
+  /* Destructor.  */
+  ~switch_conversion ();
+
+  /* The following function is invoked on every switch statement (the current
+     one is given in SWTCH) and runs the individual phases of switch
+     conversion on it one after another until one fails or the conversion
+     is completed.  On success, NULL is in m_reason, otherwise points
+     to a string with the reason why the conversion failed.  */
+  void expand (gswitch *swtch);
+
+  /* Collection information about SWTCH statement.  */
+  void collect (gswitch *swtch);
+
+  /* Checks whether the range given by individual case statements of the switch
+     switch statement isn't too big and whether the number of branches actually
+     satisfies the size of the new array.  */
+  bool check_range ();
+
+  /* Checks whether all but the final BB basic blocks are empty.  */
+  bool check_all_empty_except_final ();
+
+  /* This function checks whether all required values in phi nodes in final_bb
+     are constants.  Required values are those that correspond to a basic block
+     which is a part of the examined switch statement.  It returns true if the
+     phi nodes are OK, otherwise false.  */
+  bool check_final_bb ();
+
+  /* The following function allocates default_values, target_{in,out}_names and
+     constructors arrays.  The last one is also populated with pointers to
+     vectors that will become constructors of new arrays.  */
+  void create_temp_arrays ();
+
+  /* Populate the array of default values in the order of phi nodes.
+     DEFAULT_CASE is the CASE_LABEL_EXPR for the default switch branch
+     if the range is non-contiguous or the default case has standard
+     structure, otherwise it is the first non-default case instead.  */
+  void gather_default_values (tree default_case);
+
+  /* The following function populates the vectors in the constructors array with
+     future contents of the static arrays.  The vectors are populated in the
+     order of phi nodes.  */
+  void build_constructors ();
+
+  /* If all values in the constructor vector are the same, return the value.
+     Otherwise return NULL_TREE.  Not supposed to be called for empty
+     vectors.  */
+  tree contains_same_values_p (vec<constructor_elt, va_gc> *vec);
+
+  /* Return type which should be used for array elements, either TYPE's
+     main variant or, for integral types, some smaller integral type
+     that can still hold all the constants.  */
+  tree array_value_type (tree type, int num);
+
+  /* Create an appropriate array type and declaration and assemble a static
+     array variable.  Also create a load statement that initializes
+     the variable in question with a value from the static array.  SWTCH is
+     the switch statement being converted, NUM is the index to
+     arrays of constructors, default values and target SSA names
+     for this particular array.  ARR_INDEX_TYPE is the type of the index
+     of the new array, PHI is the phi node of the final BB that corresponds
+     to the value that will be loaded from the created array.  TIDX
+     is an ssa name of a temporary variable holding the index for loads from the
+     new array.  */
+  void build_one_array (int num, tree arr_index_type,
+			gphi *phi, tree tidx);
+
+  /* Builds and initializes static arrays initialized with values gathered from
+     the switch statement.  Also creates statements that load values from
+     them.  */
+  void build_arrays ();
+
+  /* Generates and appropriately inserts loads of default values at the position
+     given by GSI.  Returns the last inserted statement.  */
+  gassign *gen_def_assigns (gimple_stmt_iterator *gsi);
+
+  /* Deletes the unused bbs and edges that now contain the switch statement and
+     its empty branch bbs.  BBD is the now dead BB containing
+     the original switch statement, FINAL is the last BB of the converted
+     switch statement (in terms of succession).  */
+  void prune_bbs (basic_block bbd, basic_block final, basic_block default_bb);
+
+  /* Add values to phi nodes in final_bb for the two new edges.  E1F is the edge
+     from the basic block loading values from an array and E2F from the basic
+     block loading default values.  BBF is the last switch basic block (see the
+     bbf description in the comment below).  */
+  void fix_phi_nodes (edge e1f, edge e2f, basic_block bbf);
+
+  /* Creates a check whether the switch expression value actually falls into the
+     range given by all the cases.  If it does not, the temporaries are loaded
+     with default values instead.  */
+  void gen_inbound_check ();
+
+  /* Switch statement for which switch conversion takes place.  */
+  gswitch *m_switch;
+
+  /* The expression used to decide the switch branch.  */
+  tree m_index_expr;
+
+  /* The following integer constants store the minimum and maximum value
+     covered by the case labels.  */
+  tree m_range_min;
+  tree m_range_max;
+
+  /* The difference between the above two numbers.  Stored here because it
+     is used in all the conversion heuristics, as well as for some of the
+     transformation, and it is expensive to re-compute it all the time.  */
+  tree m_range_size;
+
+  /* Basic block that contains the actual GIMPLE_SWITCH.  */
+  basic_block m_switch_bb;
+
+  /* Basic block that is the target of the default case.  */
+  basic_block m_default_bb;
+
+  /* The single successor block of all branches out of the GIMPLE_SWITCH,
+     if such a block exists.  Otherwise NULL.  */
+  basic_block m_final_bb;
+
+  /* The probability of the default edge in the replaced switch.  */
+  profile_probability m_default_prob;
+
+  /* The count of the default edge in the replaced switch.  */
+  profile_count m_default_count;
+
+  /* Combined count of all other (non-default) edges in the replaced switch.  */
+  profile_count m_other_count;
+
+  /* Number of phi nodes in the final bb (that we'll be replacing).  */
+  int m_phi_count;
+
+  /* Constructors of new static arrays.  */
+  vec<constructor_elt, va_gc> **m_constructors;
+
+  /* Array of default values, in the same order as phi nodes.  */
+  tree *m_default_values;
+
+  /* Array of ssa names that are initialized with a value from a new static
+     array.  */
+  tree *m_target_inbound_names;
+
+  /* Array of ssa names that are initialized with the default value if the
+     switch expression is out of range.  */
+  tree *m_target_outbound_names;
+
+  /* VOP SSA_NAME.  */
+  tree m_target_vop;
+
+  /* The first load statement that loads a temporary from a new static array.
+   */
+  gimple *m_arr_ref_first;
+
+  /* The last load statement that loads a temporary from a new static array.  */
+  gimple *m_arr_ref_last;
+
+  /* String reason why the case wasn't a good candidate that is written to the
+     dump file, if there is one.  */
+  const char *m_reason;
+
+  /* True if default case is not used for any value between range_min and
+     range_max inclusive.  */
+  bool m_contiguous_range;
+
+  /* True if default case does not have the required shape for other case
+     labels.  */
+  bool m_default_case_nonstandard;
+
+  /* Count is number of non-default edges.  */
+  unsigned int m_count;
+
+  /* True if CFG has been changed.  */
+  bool m_cfg_altered;
+};
+
+} // tree_switch_conversion namespace
+
+#endif // TREE_SWITCH_CONVERSION_H