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 "irgraph_t.h"
22 #include "iropt_dbg.h"
25 #include "reassoc_t.h"
30 DEBUG_ONLY(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 REGION_CONST = 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
45 * is loop invariant (called region constant)
47 * @param n the node to be checked for constant
48 * @param block a block that might be in a loop
50 static const_class_t get_const_class(ir_node *n, ir_node *block)
52 ir_op *op = get_irn_op(n);
57 /* although SymConst's are of course real constant, we cannot
58 fold them, so handle them like region constants */
59 if (op == op_SymConst)
63 * Beware: Bad nodes are always loop-invariant, but
64 * cannot handled in later code, so filter them here.
66 if (! is_Bad(n) && is_loop_invariant(n, block))
73 * returns the operands of a commutative bin-op, if one operand is
74 * a region constant, it is returned as the second one.
76 * Beware: Real constants must be returned with higher priority than
77 * region constants, because they might be folded.
79 static void get_comm_Binop_ops(ir_node *binop, ir_node **a, ir_node **c)
81 ir_node *op_a = get_binop_left(binop);
82 ir_node *op_b = get_binop_right(binop);
83 ir_node *block = get_nodes_block(binop);
84 int class_a = get_const_class(op_a, block);
85 int class_b = get_const_class(op_b, block);
87 assert(is_op_commutative(get_irn_op(binop)));
89 switch (class_a + 2*class_b) {
90 case REAL_CONSTANT + 2*NO_CONSTANT:
91 case REAL_CONSTANT + 2*REAL_CONSTANT:
92 case REAL_CONSTANT + 2*REGION_CONST:
93 case REGION_CONST + 2*NO_CONSTANT:
105 * reassociate a Sub: x - c = (-c) + x
107 static int reassoc_Sub(ir_node **in)
110 ir_node *block = get_nodes_block(n);
111 ir_node *right = get_Sub_right(n);
113 /* FIXME: Do not apply this rule for unsigned Sub's because our code
114 * generation is currently buggy :-)
116 if (! mode_is_signed(get_irn_mode(n)))
120 * convert x - c => (-c) + x
122 * As there is NO real Minus in Firm it makes no sense to do this
123 * for non-real constants yet.
125 if (get_const_class(right, block) == REAL_CONSTANT) {
126 ir_node *left = get_Sub_left(n);
127 ir_node *block = get_nodes_block(n);
128 ir_mode *mode = get_irn_mode(n);
129 dbg_info *dbi = get_irn_dbg_info(n);
132 switch (get_const_class(left, block)) {
134 irn = optimize_in_place(n);
144 /* already constant, nothing to do */
148 c = new_r_Const(current_ir_graph, block, mode, get_mode_null(mode));
149 irn = new_rd_Sub(dbi, current_ir_graph, block, c, right, mode);
151 irn = new_rd_Add(dbi, current_ir_graph, block, left, irn, get_irn_mode(n));
153 DBG((dbg, LEVEL_5, "Applied: %n - %n => %n + (-%n)\n",
154 get_Sub_left(n), c, get_Sub_left(n), c));
164 /** Retrieve a mode from the operands. We need this, because
165 * Add and Sub are allowed to operate on (P, Is)
167 static ir_mode *get_mode_from_ops(ir_node *op1, ir_node *op2)
171 m1 = get_irn_mode(op1);
172 if (mode_is_reference(m1))
175 m2 = get_irn_mode(op2);
176 if (mode_is_reference(m2))
185 * reassociate a commutative Binop
187 * BEWARE: this rule leads to a potential loop, if
188 * two operands are region constants and the third is a
189 * constant, so avoid this situation.
191 static int reassoc_commutative(ir_node **node)
194 ir_op *op = get_irn_op(n);
195 ir_node *block = get_nodes_block(n);
198 get_comm_Binop_ops(n, &t1, &c1);
200 if (get_irn_op(t1) == op) {
202 const_class_t c_c1, c_c2, c_t2;
204 get_comm_Binop_ops(t1, &t2, &c2);
206 /* do not optimize Bad nodes, will fail later */
210 c_c1 = get_const_class(c1, block);
211 c_c2 = get_const_class(c2, block);
212 c_t2 = get_const_class(t2, block);
214 if ( ((c_c1 > NO_CONSTANT) & (c_t2 > NO_CONSTANT)) &&
215 ((((c_c1 ^ c_c2 ^ c_t2) & REGION_CONST) == 0) || ((c_c1 & c_c2 & c_t2) == REGION_CONST)) ) {
216 /* All three are constant and either all are constant expressions or two of them are:
217 * then applying this rule would lead into a cycle
219 * Note that if t2 is a constant so is c2 hence we save one test.
224 if ((c_c1 != NO_CONSTANT) & (c_c2 != NO_CONSTANT)) {
225 /* handles rules R7, R8, R9, R10:
226 * convert c1 .OP. (c2 .OP. x) => (c1 .OP. c2) .OP. x
228 ir_node *irn, *in[2];
229 ir_mode *mode, *mode_c1 = get_irn_mode(c1), *mode_c2 = get_irn_mode(c2);
231 /* It might happen, that c1 and c2 have different modes, for instance Is and Iu.
234 if (mode_c1 != mode_c2) {
235 if (mode_is_int(mode_c1) && mode_is_int(mode_c2)) {
236 /* get the bigger one */
237 if (get_mode_size_bits(mode_c1) > get_mode_size_bits(mode_c2))
238 c2 = new_r_Conv(current_ir_graph, block, c2, mode_c1);
239 else if (get_mode_size_bits(mode_c1) < get_mode_size_bits(mode_c2))
240 c1 = new_r_Conv(current_ir_graph, block, c1, mode_c2);
242 /* Try to cast the real const */
243 if (c_c1 == REAL_CONSTANT)
244 c1 = new_r_Conv(current_ir_graph, block, c1, mode_c2);
246 c2 = new_r_Conv(current_ir_graph, block, c2, mode_c1);
254 mode = get_mode_from_ops(in[0], in[1]);
255 in[0] = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
258 mode = get_mode_from_ops(in[0], in[1]);
259 irn = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
261 DBG((dbg, LEVEL_5, "Applied: %n .%s. (%n .%s. %n) => (%n .%s. %n) .%s. %n\n",
262 c1, get_irn_opname(n), c2, get_irn_opname(n),
263 t2, c1, get_irn_opname(n), c2, get_irn_opname(n), t2));
265 * In some rare cases it can really happen that we get the same node back.
266 * This might be happen in dead loops, were the Phi nodes are already gone away.
279 #define reassoc_Add reassoc_commutative
280 #define reassoc_And reassoc_commutative
281 #define reassoc_Or reassoc_commutative
282 #define reassoc_Eor reassoc_commutative
285 * reassociate using distributive law for Mul and Add/Sub
287 static int reassoc_Mul(ir_node **node)
290 ir_node *add_sub, *c;
293 if (reassoc_commutative(&n))
296 get_comm_Binop_ops(n, &add_sub, &c);
297 op = get_irn_op(add_sub);
299 /* handles rules R11, R12, R13, R14, R15, R16, R17, R18, R19, R20 */
300 if (op == op_Add || op == op_Sub) {
301 ir_mode *mode = get_irn_mode(n);
302 ir_node *irn, *block, *t1, *t2, *in[2];
304 block = get_nodes_block(n);
305 t1 = get_binop_left(add_sub);
306 t2 = get_binop_right(add_sub);
308 /* we can only multiplication rules on integer arithmetic */
309 if (mode_is_int(get_irn_mode(t1)) && mode_is_int(get_irn_mode(t2))) {
310 in[0] = new_rd_Mul(NULL, current_ir_graph, block, c, t1, mode);
311 in[1] = new_rd_Mul(NULL, current_ir_graph, block, c, t2, mode);
313 mode = get_mode_from_ops(in[0], in[1]);
314 irn = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
316 /* In some cases it might happen that the new irn is equal the old one, for
318 * (x - 1) * y == x * y - y
319 * will be transformed back by simpler optimization
320 * We could switch simple optimizations off, but this only happens iff y
321 * is a loop-invariant expression and that it is not clear if the new form
323 * So, we let the old one.
326 DBG((dbg, LEVEL_5, "Applied: (%n .%s. %n) %n %n => (%n %n %n) .%s. (%n %n %n)\n",
327 t1, get_op_name(op), t2, n, c, t1, n, c, get_op_name(op), t2, n, c));
339 * The walker for the reassociation.
341 static void do_reassociation(ir_node *n, void *env)
343 walker_t *wenv = env;
348 /* reassociation must run until a fixpoint is reached. */
350 ir_op *op = get_irn_op(n);
351 ir_mode *mode = get_irn_mode(n);
355 /* reassociation works only for integer or reference modes */
356 if (op->ops.reassociate && (mode_is_int(mode) || mode_is_reference(mode))) {
357 res = op->ops.reassociate(&n);
359 wenv->changes |= res;
367 * do the reassociation
369 void optimize_reassociation(ir_graph *irg)
372 irg_loopinfo_state state;
374 assert(get_irg_phase_state(irg) != phase_building);
375 assert(get_irg_pinned(irg) != op_pin_state_floats &&
376 "Reassociation needs pinned graph to work properly");
378 /* reassociation needs constant folding */
379 if (!get_opt_reassociation() || !get_opt_constant_folding())
383 * Calculate loop info, so we could identify loop-invariant
384 * code and threat it like a constant.
385 * We only need control flow loops here but can handle generic
386 * INTRA info as well.
388 state = get_irg_loopinfo_state(irg);
389 if ((state & loopinfo_inter) ||
390 (state & (loopinfo_constructed | loopinfo_valid)) != (loopinfo_constructed | loopinfo_valid))
391 construct_cf_backedges(irg);
395 /* now we have collected enough information, optimize */
396 irg_walk_graph(irg, NULL, do_reassociation, &env);
398 /* Handle graph state */
400 set_irg_outs_inconsistent(irg);
401 set_irg_loopinfo_inconsistent(irg);
405 /* Sets the default reassociation operation for an ir_op_ops. */
406 ir_op_ops *firm_set_default_reassoc(opcode code, ir_op_ops *ops)
408 #define CASE(a) case iro_##a: ops->reassociate = reassoc_##a; break
425 /* initialize the reassociation by adding operations to some opcodes */
426 void firm_init_reassociation(void)
428 FIRM_DBG_REGISTER(dbg, "firm.opt.reassoc");