1 /* Global, SSA-based optimizations using mathematical identities.
2 Copyright (C) 2005 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by the
8 Free Software Foundation; either version 2, or (at your option) any
11 GCC is distributed in the hope that it will be useful, but WITHOUT
12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING. If not, write to the Free
18 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
21 /* Currently, the only mini-pass in this file tries to CSE reciprocal
22 operations. These are common in sequences such as this one:
24 modulus = sqrt(x*x + y*y + z*z);
29 that can be optimized to
31 modulus = sqrt(x*x + y*y + z*z);
32 rmodulus = 1.0 / modulus;
37 We do this for loop invariant divisors, and with this pass whenever
38 we notice that a division has the same divisor multiple times. */
42 #include "coretypes.h"
46 #include "tree-flow.h"
49 #include "tree-pass.h"
52 gate_cse_reciprocals (void)
54 return optimize && !optimize_size && flag_unsafe_math_optimizations;
57 /* Check if DEF's uses include more than one floating-point division,
58 and if so replace them by multiplications with the reciprocal. If
59 PHI is true, insert the reciprocal calculation before BSI, otherwise
60 insert it after and move BSI to the new statement.
62 Does not check the type of DEF, nor that DEF is a GIMPLE register.
63 This is done in the caller for speed, because otherwise this routine
64 would be called for every definition and phi node. */
66 execute_cse_reciprocals_1 (block_stmt_iterator *bsi, tree def, bool phi)
69 imm_use_iterator use_iter;
70 tree t, new_stmt, type;
72 bool ok = !flag_trapping_math;
75 FOR_EACH_IMM_USE_FAST (use_p, use_iter, def)
77 tree use_stmt = USE_STMT (use_p);
78 if (TREE_CODE (use_stmt) == MODIFY_EXPR
79 && TREE_CODE (TREE_OPERAND (use_stmt, 1)) == RDIV_EXPR
80 && TREE_OPERAND (TREE_OPERAND (use_stmt, 1), 1) == def)
83 /* Check if this use post-dominates the insertion point. */
84 if (ok || dominated_by_p (CDI_POST_DOMINATORS, bsi->bb,
85 bb_for_stmt (use_stmt)))
95 /* Make a variable with the replacement and substitute it. */
96 type = TREE_TYPE (def);
97 t = make_rename_temp (type, "reciptmp");
98 new_stmt = build2 (MODIFY_EXPR, void_type_node, t,
99 fold_build2 (RDIV_EXPR, type, build_real (type, dconst1),
103 bsi_insert_before (bsi, new_stmt, BSI_SAME_STMT);
105 bsi_insert_after (bsi, new_stmt, BSI_NEW_STMT);
107 FOR_EACH_IMM_USE_SAFE (use_p, use_iter, def)
109 tree use_stmt = USE_STMT (use_p);
110 if (use_stmt != new_stmt
111 && TREE_CODE (use_stmt) == MODIFY_EXPR
112 && TREE_CODE (TREE_OPERAND (use_stmt, 1)) == RDIV_EXPR
113 && TREE_OPERAND (TREE_OPERAND (use_stmt, 1), 1) == def)
115 TREE_SET_CODE (TREE_OPERAND (use_stmt, 1), MULT_EXPR);
122 execute_cse_reciprocals (void)
126 if (flag_trapping_math)
127 calculate_dominance_info (CDI_POST_DOMINATORS);
131 block_stmt_iterator bsi;
133 for (bsi = bsi_start (bb);
134 !bsi_end_p (bsi) && TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR;
138 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
140 def = PHI_RESULT (phi);
141 if (FLOAT_TYPE_P (TREE_TYPE (def))
142 && is_gimple_reg (def))
143 execute_cse_reciprocals_1 (&bsi, def, true);
146 for (; !bsi_end_p (bsi); bsi_next (&bsi))
148 tree stmt = bsi_stmt (bsi);
149 if (TREE_CODE (stmt) == MODIFY_EXPR
150 && (def = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_DEF)) != NULL
151 && FLOAT_TYPE_P (TREE_TYPE (def))
152 && is_gimple_reg (def))
153 execute_cse_reciprocals_1 (&bsi, def, false);
157 if (flag_trapping_math)
158 free_dominance_info (CDI_POST_DOMINATORS);
161 struct tree_opt_pass pass_cse_reciprocals =
164 gate_cse_reciprocals, /* gate */
165 execute_cse_reciprocals, /* execute */
168 0, /* static_pass_number */
170 PROP_ssa, /* properties_required */
171 0, /* properties_provided */
172 0, /* properties_destroyed */
173 0, /* todo_flags_start */
174 TODO_dump_func | TODO_update_ssa | TODO_verify_ssa
175 | TODO_verify_stmts, /* todo_flags_finish */