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"
30 static firm_dbg_module_t *dbg;
32 typedef struct _walker_t {
33 int changes; /* set, if a reassociation take place */
37 NO_CONSTANT = 0, /**< node is not constant */
38 REAL_CONSTANT = 1, /**< node is a Const that is suitable for constant folding */
39 CONST_EXPR = 4 /**< node is a constant expression in the current context,
40 use 4 here to simplify implementation of get_comm_Binop_ops() */
44 * returns whether a node is constant, ie is a constant or
47 static const_class_t get_const_class(ir_node *n)
49 ir_op *op = get_irn_op(n);
53 if (op == op_SymConst)
60 * returns the operands of a commutative bin-op, if one operand is
61 * a constant in the current context, it is returned as the second one.
63 * Beware: Real constants must be returned with higher priority than
64 * constant expression, because they might be folded.
66 static void get_comm_Binop_ops(ir_node *binop, ir_node **a, ir_node **c)
68 ir_node *op_a = get_binop_left(binop);
69 ir_node *op_b = get_binop_right(binop);
70 int class_a = get_const_class(op_a);
71 int class_b = get_const_class(op_b);
73 assert(is_op_commutative(get_irn_op(binop)));
75 switch (class_a + 2*class_b) {
76 case REAL_CONSTANT + 2*NO_CONSTANT:
77 case REAL_CONSTANT + 2*REAL_CONSTANT:
78 case REAL_CONSTANT + 2*CONST_EXPR:
79 case CONST_EXPR + 2*NO_CONSTANT:
91 * reassociate a Sub: x - c = (-c) + x
93 static int reassoc_Sub(ir_node **in)
96 ir_node *right = get_Sub_right(n);
98 /* FIXME: Do not apply this rule for unsigned Sub's because our code
99 * generation is currently buggy :-)
101 if (! mode_is_signed(get_irn_mode(n)))
105 * convert x - c => (-c) + x
107 * As there is NO real Minus in Firm it makes no sense to do this
108 * for non-real constants yet.
110 if (get_const_class(right) == REAL_CONSTANT) {
111 ir_node *left = get_Sub_left(n);
112 ir_node *block = get_nodes_block(n);
113 ir_mode *mode = get_irn_mode(n);
114 dbg_info *dbi = get_irn_dbg_info(n);
117 switch (get_const_class(left)) {
119 irn = optimize_in_place(n);
129 /* already constant, nothing to do */
133 c = new_r_Const(current_ir_graph, block, mode, get_mode_null(mode));
134 irn = new_rd_Sub(dbi, current_ir_graph, block, c, right, mode);
136 irn = new_rd_Add(dbi, current_ir_graph, block, left, irn, get_irn_mode(n));
138 DBG((dbg, LEVEL_5, "Applied: %n - %n => %n + (-%n)\n",
139 get_Sub_left(n), c, get_Sub_left(n), c));
149 /** Retrieve a mode form the operands. We need this, because
150 * Add and Sub are allowed to operate on (P, Is)
152 static ir_mode *get_mode_from_ops(ir_node *op1, ir_node *op2)
156 m1 = get_irn_mode(op1);
157 if (mode_is_reference(m1))
160 m2 = get_irn_mode(op2);
161 if (mode_is_reference(m2))
170 * reassociate a commutative Binop
172 * BEWARE: this rule leads to a potential loop, if
173 * all two operands are are constant expressions and the third is a
174 * constant, so avoid this situation.
176 static int reassoc_commutative(ir_node **node)
179 ir_op *op = get_irn_op(n);
180 ir_node *block = get_nodes_block(n);
183 get_comm_Binop_ops(n, &t1, &c1);
185 if (get_irn_op(t1) == op) {
187 const_class_t c_c1, c_c2, c_t2;
189 get_comm_Binop_ops(t1, &t2, &c2);
191 /* do not optimize Bad nodes, will fail later */
195 c_c1 = get_const_class(c1);
196 c_c2 = get_const_class(c2);
197 c_t2 = get_const_class(t2);
199 if ( ((c_c1 > NO_CONSTANT) & (c_t2 > NO_CONSTANT)) &&
200 ((((c_c1 ^ c_c2 ^ c_t2) & CONST_EXPR) == 0) || ((c_c1 & c_c2 & c_t2) == CONST_EXPR)) ) {
201 /* all three are constant and either all are constant expressions or two of them are:
202 * then, applying this rule would lead into a cycle
204 * Note that if t2 is a constant so is c2, so we save one test.
209 if ((c_c1 != NO_CONSTANT) & (c_c2 != NO_CONSTANT)) {
210 /* handles rules R7, R8, R9, R10:
211 * convert c1 .OP. (c2 .OP. x) => (c1 .OP. c2) .OP. x
213 ir_node *irn, *in[2];
214 ir_mode *mode, *mode_c1 = get_irn_mode(c1), *mode_c2 = get_irn_mode(c2);
216 /* It might happen, that c1 and c2 have different modes, for instance Is and Iu.
219 if (mode_c1 != mode_c2) {
220 if (mode_is_int(mode_c1) && mode_is_int(mode_c2)) {
221 /* get the bigger one */
222 if (get_mode_size_bits(mode_c1) > get_mode_size_bits(mode_c2))
223 c2 = new_r_Conv(current_ir_graph, block, c2, mode_c1);
224 else if (get_mode_size_bits(mode_c1) < get_mode_size_bits(mode_c2))
225 c1 = new_r_Conv(current_ir_graph, block, c1, mode_c2);
227 /* Try to cast the real const */
228 if (c_c1 == REAL_CONSTANT)
229 c1 = new_r_Conv(current_ir_graph, block, c1, mode_c2);
231 c2 = new_r_Conv(current_ir_graph, block, c2, mode_c1);
239 mode = get_mode_from_ops(in[0], in[1]);
240 in[0] = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
243 mode = get_mode_from_ops(in[0], in[1]);
244 irn = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
246 DBG((dbg, LEVEL_5, "Applied: %n .%s. (%n .%s. %n) => (%n .%s. %n) .%s. %n\n",
247 c1, get_irn_opname(n), c2, get_irn_opname(n),
248 t2, c1, get_irn_opname(n), c2, get_irn_opname(n), t2));
250 * in some rare cases it can really happen that we get the same node back.
251 * This might be happen in dead loops, were the Phi nodes are already gone away.
264 #define reassoc_Add reassoc_commutative
265 #define reassoc_And reassoc_commutative
266 #define reassoc_Or reassoc_commutative
267 #define reassoc_Eor reassoc_commutative
270 * reassociate using distributive law for Mul and Add/Sub
272 static int reassoc_Mul(ir_node **node)
275 ir_node *add_sub, *c;
278 if (reassoc_commutative(&n))
281 get_comm_Binop_ops(n, &add_sub, &c);
282 op = get_irn_op(add_sub);
284 /* handles rules R11, R12, R13, R14, R15, R16, R17, R18, R19, R20 */
285 if (op == op_Add || op == op_Sub) {
286 ir_mode *mode = get_irn_mode(n);
287 ir_node *irn, *block, *t1, *t2, *in[2];
289 block = get_nodes_block(n);
290 t1 = get_binop_left(add_sub);
291 t2 = get_binop_right(add_sub);
293 in[0] = new_rd_Mul(NULL, current_ir_graph, block, c, t1, mode);
294 in[1] = new_rd_Mul(NULL, current_ir_graph, block, c, t2, mode);
296 mode = get_mode_from_ops(in[0], in[1]);
297 irn = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
299 DBG((dbg, LEVEL_5, "Applied: (%n .%s. %n) %n %n => (%n %n %n) .%s. (%n %n %n)\n",
300 t1, get_op_name(op), t2, n, c, t1, n, c, get_op_name(op), t2, n, c));
310 * The walker for the reassociation
312 static void do_reassociation(ir_node *n, void *env)
314 walker_t *wenv = env;
319 /* reassociation must run until fixpoint */
321 ir_op *op = get_irn_op(n);
322 ir_mode *mode = get_irn_mode(n);
326 /* reassociation works only for integer or reference modes */
327 if (op->reassociate && (mode_is_int(mode) || mode_is_reference(mode))) {
328 res = op->reassociate(&n);
330 wenv->changes |= res;
338 * do the reassociation
340 void optimize_reassociation(ir_graph *irg)
344 assert(get_irg_phase_state(irg) != phase_building);
346 /* reassociation needs constant folding */
347 if (!get_opt_reassociation() || !get_opt_constant_folding())
352 irg_walk_graph(irg, NULL, do_reassociation, &env);
354 /* now we have collected enough information, optimize */
355 irg_walk_graph(irg, NULL, do_reassociation, &env);
357 /* Handle graph state */
359 if (get_irg_outs_state(current_ir_graph) == outs_consistent)
360 set_irg_outs_inconsistent(current_ir_graph);
364 /* initialize the reassociation by adding operations to some opcodes */
365 void firm_init_reassociation(void)
367 #define INIT(a) op_##a->reassociate = reassoc_##a;
376 dbg = firm_dbg_register("firm.opt.reassoc");
377 firm_dbg_set_mask(dbg, -1);