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"
31 static firm_dbg_module_t *dbg;
33 typedef struct _walker_t {
34 int changes; /* set, if a reassociation take place */
38 NO_CONSTANT = 0, /**< node is not constant */
39 REAL_CONSTANT = 1, /**< node is a Const that is suitable for constant folding */
40 CONST_EXPR = 4 /**< node is a constant expression in the current context,
41 use 4 here to simplify implementation of get_comm_Binop_ops() */
45 * returns whether a node is constant ie is a constant or
48 * @param n the node to be checked for constant
49 * @param block a block that might be in a loop
51 static const_class_t get_const_class(ir_node *n, ir_node *block)
53 ir_op *op = get_irn_op(n);
57 if (op == op_SymConst)
60 * Beware: Bad nodes are always loop-invariant, but
61 * cannot handles in later code, so filter them here
63 if (! is_Bad(n) && is_loop_invariant(n, block))
70 * returns the operands of a commutative bin-op, if one operand is
71 * a constant in the current context, it is returned as the second one.
73 * Beware: Real constants must be returned with higher priority than
74 * constant expression, because they might be folded.
76 static void get_comm_Binop_ops(ir_node *binop, ir_node **a, ir_node **c)
78 ir_node *op_a = get_binop_left(binop);
79 ir_node *op_b = get_binop_right(binop);
80 ir_node *block = get_nodes_block(binop);
81 int class_a = get_const_class(op_a, block);
82 int class_b = get_const_class(op_b, block);
84 assert(is_op_commutative(get_irn_op(binop)));
86 switch (class_a + 2*class_b) {
87 case REAL_CONSTANT + 2*NO_CONSTANT:
88 case REAL_CONSTANT + 2*REAL_CONSTANT:
89 case REAL_CONSTANT + 2*CONST_EXPR:
90 case CONST_EXPR + 2*NO_CONSTANT:
102 * reassociate a Sub: x - c = (-c) + x
104 static int reassoc_Sub(ir_node **in)
107 ir_node *block = get_nodes_block(n);
108 ir_node *right = get_Sub_right(n);
110 /* FIXME: Do not apply this rule for unsigned Sub's because our code
111 * generation is currently buggy :-)
113 if (! mode_is_signed(get_irn_mode(n)))
117 * convert x - c => (-c) + x
119 * As there is NO real Minus in Firm it makes no sense to do this
120 * for non-real constants yet.
122 if (get_const_class(right, block) == REAL_CONSTANT) {
123 ir_node *left = get_Sub_left(n);
124 ir_node *block = get_nodes_block(n);
125 ir_mode *mode = get_irn_mode(n);
126 dbg_info *dbi = get_irn_dbg_info(n);
129 switch (get_const_class(left, block)) {
131 irn = optimize_in_place(n);
141 /* already constant, nothing to do */
145 c = new_r_Const(current_ir_graph, block, mode, get_mode_null(mode));
146 irn = new_rd_Sub(dbi, current_ir_graph, block, c, right, mode);
148 irn = new_rd_Add(dbi, current_ir_graph, block, left, irn, get_irn_mode(n));
150 DBG((dbg, LEVEL_5, "Applied: %n - %n => %n + (-%n)\n",
151 get_Sub_left(n), c, get_Sub_left(n), c));
161 /** Retrieve a mode from the operands. We need this, because
162 * Add and Sub are allowed to operate on (P, Is)
164 static ir_mode *get_mode_from_ops(ir_node *op1, ir_node *op2)
168 m1 = get_irn_mode(op1);
169 if (mode_is_reference(m1))
172 m2 = get_irn_mode(op2);
173 if (mode_is_reference(m2))
182 * reassociate a commutative Binop
184 * BEWARE: this rule leads to a potential loop, if
185 * two operands are are constant expressions and the third is a
186 * constant, so avoid this situation.
188 static int reassoc_commutative(ir_node **node)
191 ir_op *op = get_irn_op(n);
192 ir_node *block = get_nodes_block(n);
195 get_comm_Binop_ops(n, &t1, &c1);
197 if (get_irn_op(t1) == op) {
199 const_class_t c_c1, c_c2, c_t2;
201 get_comm_Binop_ops(t1, &t2, &c2);
203 /* do not optimize Bad nodes, will fail later */
207 c_c1 = get_const_class(c1, block);
208 c_c2 = get_const_class(c2, block);
209 c_t2 = get_const_class(t2, block);
211 if ( ((c_c1 > NO_CONSTANT) & (c_t2 > NO_CONSTANT)) &&
212 ((((c_c1 ^ c_c2 ^ c_t2) & CONST_EXPR) == 0) || ((c_c1 & c_c2 & c_t2) == CONST_EXPR)) ) {
213 /* All three are constant and either all are constant expressions or two of them are:
214 * then applying this rule would lead into a cycle
216 * Note that if t2 is a constant so is c2 hence we save one test.
221 if ((c_c1 != NO_CONSTANT) & (c_c2 != NO_CONSTANT)) {
222 /* handles rules R7, R8, R9, R10:
223 * convert c1 .OP. (c2 .OP. x) => (c1 .OP. c2) .OP. x
225 ir_node *irn, *in[2];
226 ir_mode *mode, *mode_c1 = get_irn_mode(c1), *mode_c2 = get_irn_mode(c2);
228 /* It might happen, that c1 and c2 have different modes, for instance Is and Iu.
231 if (mode_c1 != mode_c2) {
232 if (mode_is_int(mode_c1) && mode_is_int(mode_c2)) {
233 /* get the bigger one */
234 if (get_mode_size_bits(mode_c1) > get_mode_size_bits(mode_c2))
235 c2 = new_r_Conv(current_ir_graph, block, c2, mode_c1);
236 else if (get_mode_size_bits(mode_c1) < get_mode_size_bits(mode_c2))
237 c1 = new_r_Conv(current_ir_graph, block, c1, mode_c2);
239 /* Try to cast the real const */
240 if (c_c1 == REAL_CONSTANT)
241 c1 = new_r_Conv(current_ir_graph, block, c1, mode_c2);
243 c2 = new_r_Conv(current_ir_graph, block, c2, mode_c1);
251 mode = get_mode_from_ops(in[0], in[1]);
252 in[0] = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
255 mode = get_mode_from_ops(in[0], in[1]);
256 irn = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
258 DBG((dbg, LEVEL_5, "Applied: %n .%s. (%n .%s. %n) => (%n .%s. %n) .%s. %n\n",
259 c1, get_irn_opname(n), c2, get_irn_opname(n),
260 t2, c1, get_irn_opname(n), c2, get_irn_opname(n), t2));
262 * In some rare cases it can really happen that we get the same node back.
263 * This might be happen in dead loops, were the Phi nodes are already gone away.
276 #define reassoc_Add reassoc_commutative
277 #define reassoc_And reassoc_commutative
278 #define reassoc_Or reassoc_commutative
279 #define reassoc_Eor reassoc_commutative
282 * reassociate using distributive law for Mul and Add/Sub
284 static int reassoc_Mul(ir_node **node)
287 ir_node *add_sub, *c;
290 if (reassoc_commutative(&n))
293 get_comm_Binop_ops(n, &add_sub, &c);
294 op = get_irn_op(add_sub);
296 /* handles rules R11, R12, R13, R14, R15, R16, R17, R18, R19, R20 */
297 if (op == op_Add || op == op_Sub) {
298 ir_mode *mode = get_irn_mode(n);
299 ir_node *irn, *block, *t1, *t2, *in[2];
301 block = get_nodes_block(n);
302 t1 = get_binop_left(add_sub);
303 t2 = get_binop_right(add_sub);
305 in[0] = new_rd_Mul(NULL, current_ir_graph, block, c, t1, mode);
306 in[1] = new_rd_Mul(NULL, current_ir_graph, block, c, t2, mode);
308 mode = get_mode_from_ops(in[0], in[1]);
309 irn = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
311 DBG((dbg, LEVEL_5, "Applied: (%n .%s. %n) %n %n => (%n %n %n) .%s. (%n %n %n)\n",
312 t1, get_op_name(op), t2, n, c, t1, n, c, get_op_name(op), t2, n, c));
322 * The walker for the reassociation.
324 static void do_reassociation(ir_node *n, void *env)
326 walker_t *wenv = env;
331 /* Reassociation must run until a fixpoint is reached. */
333 ir_op *op = get_irn_op(n);
334 ir_mode *mode = get_irn_mode(n);
338 /* reassociation works only for integer or reference modes */
339 if (op->reassociate && (mode_is_int(mode) || mode_is_reference(mode))) {
340 res = op->reassociate(&n);
342 wenv->changes |= res;
350 * do the reassociation
352 void optimize_reassociation(ir_graph *irg)
355 irg_loopinfo_state state;
357 assert(get_irg_phase_state(irg) != phase_building);
359 /* reassociation needs constant folding */
360 if (!get_opt_reassociation() || !get_opt_constant_folding())
364 * Calculate loop info, so we could identify loop-invariant
365 * code and threat it like a constant.
366 * We only need control flow loops here but can handle generic
367 * INTRA info as well.
369 state = get_irg_loopinfo_state(irg);
370 if ((state & loopinfo_inter) ||
371 (state & (loopinfo_constructed | loopinfo_valid)) != (loopinfo_constructed | loopinfo_valid))
372 construct_cf_backedges(irg);
376 /* now we have collected enough information, optimize */
377 irg_walk_graph(irg, NULL, do_reassociation, &env);
379 /* Handle graph state */
381 if (get_irg_outs_state(irg) == outs_consistent)
382 set_irg_outs_inconsistent(irg);
383 set_irg_loopinfo_inconsistent(irg);
387 /* initialize the reassociation by adding operations to some opcodes */
388 void firm_init_reassociation(void)
390 #define INIT(a) op_##a->reassociate = reassoc_##a;
399 dbg = firm_dbg_register("firm.opt.reassoc");