3 * File name: ir/opt/reassoc.c
4 * Purpose: Reassociation
8 * Copyright: (c) 1998-2004 Universität Karlsruhe
9 * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
16 # include "irnode_t.h"
17 # include "irgraph_t.h"
18 # include "irmode_t.h"
20 # include "ircons_t.h"
23 # include "iropt_dbg.h"
24 # include "irflag_t.h"
26 # include "reassoc_t.h"
27 # include "firmstat.h"
29 typedef struct _walker_t {
30 int changes; /* set, if a reassociation take place */
34 NO_CONSTANT = 0, /**< node is not constant */
35 REAL_CONSTANT = 1, /**< node is a constnt that is suitable for constant folding */
36 CONST_EXPR = 4 /**< node is not constnt expression in the current context,
37 use 4 here to simplify implementation of get_comm_Binop_ops() */
41 * returns wheater a node is constant, ie is a constant or
44 static const_class_t get_const_class(ir_node *n)
46 ir_op *op = get_irn_op(n);
50 if (op == op_SymConst)
57 * returns the operands of a commutative bin-op, if one operand is
58 * a constant in the current context, it is returned as the second one.
60 * Beware: Real constrants must be returned with higher priority than
61 * constnt expression, because they might be folded.
63 static void get_comm_Binop_ops(ir_node *binop, ir_node **a, ir_node **c)
65 ir_node *op_a = get_binop_left(binop);
66 ir_node *op_b = get_binop_right(binop);
67 int class_a = get_const_class(op_a);
68 int class_b = get_const_class(op_b);
70 assert(is_op_commutative(get_irn_op(binop)));
72 switch (class_a + 2*class_b) {
73 case REAL_CONSTANT + 2*NO_CONSTANT:
74 case REAL_CONSTANT + 2*REAL_CONSTANT:
75 case REAL_CONSTANT + 2*CONST_EXPR:
76 case CONST_EXPR + 2*NO_CONSTANT:
88 * reassociate a Sub: x - c = (-c) + x
90 static int reassoc_Sub(ir_node *n)
92 ir_node *right = get_Sub_right(n);
95 * convert x - c => (-c) + x
97 * As there is NO real Minus in Firm it makes no sense to do this
98 * for non-real constants yet.
100 if (get_const_class(right) == REAL_CONSTANT) {
101 ir_node *block = get_nodes_block(right);
102 ir_mode *mode = get_irn_mode(right);
103 dbg_info *dbg = get_irn_dbg_info(right);
106 c = new_r_Const(current_ir_graph, block, mode, get_mode_null(mode));
107 irn = new_rd_Sub(dbg, current_ir_graph, block, c, right, mode);
109 irn = new_rd_Add(dbg, current_ir_graph, block, irn, get_Sub_left(n), get_irn_mode(n));
111 printf("Applied: %s - %s => (-%s) + %s\n",
112 get_irn_opname(get_Sub_left(n)), get_irn_opname(c),
113 get_irn_opname(c), get_irn_opname(get_Sub_left(n)) );
122 /** Retrieve a mode form the operands. We need this, because
123 * Add and Sub are allowed to operate on (P, Is)
125 static ir_mode *get_mode_from_ops(ir_node *op1, ir_node *op2)
129 m1 = get_irn_mode(op1);
130 if (mode_is_reference(m1))
133 m2 = get_irn_mode(op2);
134 if (mode_is_reference(m2))
143 * reassociate a commutative Binop
145 * BEWARE: this rule leads to a potential loop, if
146 * all two operands are are constant expressions and the third is a
147 * constant, so avoid this situation.
149 static int reassoc_commutative(ir_node *n)
151 ir_op *op = get_irn_op(n);
152 ir_node *block = get_nodes_block(n);
155 get_comm_Binop_ops(n, &t1, &c1);
157 if (get_irn_op(t1) == op) {
159 const_class_t c_c1, c_c2, c_t2;
161 get_comm_Binop_ops(t1, &t2, &c2);
163 c_c1 = get_const_class(c1);
164 c_c2 = get_const_class(c2);
165 c_t2 = get_const_class(t2);
167 if ( ((c_c1 > NO_CONSTANT) & (c_t2 > NO_CONSTANT)) &&
168 ((((c_c1 ^ c_c2 ^ c_t2) & CONST_EXPR) == 0) || ((c_c1 & c_c2 & c_t2) == CONST_EXPR)) ) {
169 /* all three are constant and either all are constant expressions or two of them are:
170 * then, applying this rule would lead into a cycle
172 * Note that if t2 is a onstant so is c2, so we save one test.
177 if ((c_c1 != NO_CONSTANT) & (c_c2 != NO_CONSTANT)) {
178 /* handles rules R7, R8, R9, R10:
179 * convert c1 .OP. (c2 .OP. x) => (c1 .OP. c2) .OP. x
181 ir_node *irn, *in[2];
187 mode = get_mode_from_ops(in[0], in[1]);
188 in[0] = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
191 mode = get_mode_from_ops(in[0], in[1]);
192 irn = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
194 printf("Applied: %s .%s. (%s .%s. %s) => (%s .%s. %s) .%s. %s\n",
195 get_irn_opname(c1), get_irn_opname(n), get_irn_opname(c2), get_irn_opname(n), get_irn_opname(t2),
196 get_irn_opname(c1), get_irn_opname(n), get_irn_opname(c2), get_irn_opname(n), get_irn_opname(t2));
206 #define reassoc_Add reassoc_commutative
209 * reassociate using distibutive law for Mul and Add/Sub
211 static int reassoc_Mul(ir_node *n)
213 ir_node *add_sub, *c;
216 if (reassoc_commutative(n))
219 get_comm_Binop_ops(n, &add_sub, &c);
220 op = get_irn_op(add_sub);
222 /* handles rules R11, R12, R13, R14, R15, R16, R17, R18, R19, R20 */
223 if (op == op_Add || op == op_Sub) {
224 ir_mode *mode = get_irn_mode(n);
225 ir_node *irn, *block, *t1, *t2, *in[2];
227 block = get_nodes_block(n);
228 t1 = get_binop_left(add_sub);
229 t2 = get_binop_right(add_sub);
231 in[0] = new_rd_Mul(NULL, current_ir_graph, block, c, t1, mode);
232 in[1] = new_rd_Mul(NULL, current_ir_graph, block, c, t2, mode);
234 mode = get_mode_from_ops(in[0], in[1]);
235 irn = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
237 printf("Applied: (%s .%s. %s) %s %s => (%s %s %s) .%s. (%s %s %s)\n",
238 get_irn_opname(t1), get_op_name(op), get_irn_opname(t2), get_irn_opname(n), get_irn_opname(c),
239 get_irn_opname(t1), get_irn_opname(n), get_irn_opname(c),
241 get_irn_opname(t2), get_irn_opname(n), get_irn_opname(c));
251 * The walker for the reassociation
253 static void do_reassociation(ir_node *n, void *env)
255 walker_t *wenv = env;
258 /* reassociation must run until fixpoint */
260 ir_op *op = get_irn_op(n);
261 ir_mode *mode = get_irn_mode(n);
265 /* reassociation works only for integer or reference modes */
266 if (op->reassociate && (mode_is_int(mode) || mode_is_reference(mode))) {
267 res = op->reassociate(n);
271 /* we need a skip here, or we will see an Id in the next iteration */
279 * do the reassociation
281 void optimize_reassociation(ir_graph *irg)
285 assert(get_irg_phase_state(irg) != phase_building);
287 /* reassociation needs constant folding */
288 if (!get_opt_reassociation() || !get_opt_constant_folding())
293 irg_walk_graph(irg, NULL, do_reassociation, &env);
295 /* now we have collected enough information, optimize */
296 irg_walk_graph(irg, NULL, do_reassociation, &env);
298 /* Handle graph state */
300 if (get_irg_outs_state(current_ir_graph) == outs_consistent)
301 set_irg_outs_inconsistent(current_ir_graph);
305 /* initialise the reassociation by adding operations to some opcodes */
306 void firm_init_reassociation(void)
308 #define INIT(a) op_##a->reassociate = reassoc_##a;