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22 * @brief modifies schedule so flags dependencies are respected.
23 * @author Matthias Braun, Christoph Mallon
24 * @version $Id: besched.h 14693 2007-06-21 15:35:49Z beck $
26 * Fixup schedule to respect flag constraints by moving and rematerialisation of
29 * Flags are modeled as register classes with ignore registers. However to avoid
30 * bloating the graph, only flag-consumer -> producer dependencies are
31 * explicitely modeled in the graph. Nodes that just change the flags are only
32 * marked with the arch_irn_flags_modify_flags flag.
34 * Flags are usually a limited resource that can't (or at least shouldn't) be
35 * spilled. So in some situations (for example 2 adc-nodes that use the flags of
36 * a single add node on x86) operations have to be repeated to work correctly.
46 #include "iredges_t.h"
58 static const arch_register_class_t *flag_class;
59 static const arch_register_t *flags_reg;
60 static func_rematerialize remat;
61 static check_modifies_flags check_modify;
64 static ir_node *default_remat(ir_node *node, ir_node *after)
66 ir_node *block, *copy;
70 block = get_nodes_block(after);
72 copy = exact_copy(node);
73 set_nodes_block(copy, block);
74 sched_add_after(after, copy);
79 static bool default_check_modifies(const ir_node *node)
81 return arch_irn_is(node, modify_flags);
85 * tests whether we can legally move node node after node after
86 * (only works for nodes in same block)
88 static bool can_move(ir_node *node, ir_node *after)
90 const ir_edge_t *edge;
91 ir_node *node_block = get_nodes_block(node);
92 assert(node_block == get_nodes_block(after));
94 /* TODO respect dep edges */
95 assert(get_irn_n_edges_kind(node, EDGE_KIND_DEP) == 0);
97 /** all users have to be after the after node */
98 foreach_out_edge(node, edge) {
99 ir_node *out = get_edge_src_irn(edge);
101 const ir_edge_t *edge2;
102 assert(get_irn_n_edges_kind(out, EDGE_KIND_DEP) == 0);
103 foreach_out_edge(out, edge2) {
104 ir_node *out2 = get_edge_src_irn(edge2);
105 if (get_nodes_block(out2) != node_block)
107 /* Phi or End represents a usage at block end. */
108 if (is_Phi(out2) || is_End(out2))
111 const ir_edge_t *edge3;
112 foreach_out_edge(out2, edge3) {
113 ir_node *out3 = get_edge_src_irn(edge3);
114 /* Phi or End represents a usage at block end. */
115 if (is_Phi(out3) || is_End(out3))
117 assert(!is_Sync(out3));
118 if (sched_get_time_step(out3) <= sched_get_time_step(after)) {
122 } else if (sched_get_time_step(out2) <= sched_get_time_step(after)) {
127 if (get_nodes_block(out) != node_block)
129 /* phi represents a usage at block end */
132 if (sched_get_time_step(out) <= sched_get_time_step(after)) {
141 static void rematerialize_or_move(ir_node *flags_needed, ir_node *node,
142 ir_node *flag_consumers, int pn)
148 if (!is_Block(node) &&
149 get_nodes_block(flags_needed) == get_nodes_block(node) &&
150 can_move(flags_needed, node)) {
152 sched_remove(flags_needed);
153 sched_add_after(node, flags_needed);
154 /* No need to update liveness, because the node stays in the same block */
159 copy = remat(flags_needed, node);
161 if (get_irn_mode(copy) == mode_T) {
162 ir_mode *mode = flag_class->mode;
163 value = new_rd_Proj(NULL, copy, mode, pn);
171 int arity = get_irn_arity(n);
172 for (i = 0; i < arity; ++i) {
173 ir_node *in = get_irn_n(n, i);
175 if (in == flags_needed) {
176 set_irn_n(n, i, value);
180 n = (ir_node*)get_irn_link(n);
183 /* No need to introduce the copy, because it only lives in this block, but
184 * we have to update the liveness of all operands */
185 if (is_Block(node) ||
186 get_nodes_block(node) != get_nodes_block(flags_needed)) {
187 ir_graph *irg = get_irn_irg(node);
188 be_lv_t *lv = be_get_irg_liveness(irg);
192 for (i = get_irn_arity(copy) - 1; i >= 0; --i) {
193 be_liveness_update(lv, get_irn_n(copy, i));
200 * walks up the schedule and makes sure there are no flag-destroying nodes
201 * between a flag-consumer -> flag-producer chain. Fixes problematic situations
202 * by moving and/or rematerialisation of the flag-producers.
203 * (This can be extended in the future to do some register allocation on targets
204 * like ppc32 where we conceptually have 8 flag registers)
206 static void fix_flags_walker(ir_node *block, void *env)
209 ir_node *flags_needed = NULL;
210 ir_node *flag_consumers = NULL;
214 sched_foreach_reverse(block, node) {
216 ir_node *new_flags_needed = NULL;
222 if (node == flags_needed) {
225 flag_consumers = NULL;
228 /* test whether node destroys the flags */
230 if (be_is_Keep(test))
231 test = sched_prev(test);
233 if (flags_needed != NULL && check_modify(test)) {
235 rematerialize_or_move(flags_needed, node, flag_consumers, pn);
237 flag_consumers = NULL;
240 /* test whether the current node needs flags */
241 arity = get_irn_arity(node);
242 for (i = 0; i < arity; ++i) {
243 const arch_register_class_t *cls = arch_get_irn_reg_class(node, i);
244 if (cls == flag_class) {
245 assert(new_flags_needed == NULL);
246 new_flags_needed = get_irn_n(node, i);
250 if (new_flags_needed == NULL)
253 /* spiller can't (correctly) remat flag consumers at the moment */
254 assert(!arch_irn_is(node, rematerializable));
256 if (skip_Proj(new_flags_needed) != flags_needed) {
257 if (flags_needed != NULL) {
258 /* rematerialize node */
259 rematerialize_or_move(flags_needed, node, flag_consumers, pn);
261 flag_consumers = NULL;
264 flags_needed = new_flags_needed;
265 arch_set_irn_register(flags_needed, flags_reg);
266 if (is_Proj(flags_needed)) {
267 pn = get_Proj_proj(flags_needed);
268 flags_needed = get_Proj_pred(flags_needed);
270 flag_consumers = node;
271 set_irn_link(flag_consumers, NULL);
272 assert(arch_irn_is(flags_needed, rematerializable));
274 /* link all consumers in a list */
275 set_irn_link(node, flag_consumers);
276 flag_consumers = node;
280 if (flags_needed != NULL) {
281 assert(get_nodes_block(flags_needed) != block);
282 rematerialize_or_move(flags_needed, node, flag_consumers, pn);
284 flag_consumers = NULL;
287 assert(flags_needed == NULL);
288 assert(flag_consumers == NULL);
291 void be_sched_fix_flags(ir_graph *irg, const arch_register_class_t *flag_cls,
292 func_rematerialize remat_func,
293 check_modifies_flags check_modifies_flags_func)
295 flag_class = flag_cls;
296 flags_reg = & flag_class->regs[0];
298 check_modify = check_modifies_flags_func;
301 remat = &default_remat;
302 if (check_modify == NULL)
303 check_modify = &default_check_modifies;
305 ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK);
306 irg_block_walk_graph(irg, fix_flags_walker, NULL, NULL);
307 ir_free_resources(irg, IR_RESOURCE_IRN_LINK);
310 be_remove_dead_nodes_from_schedule(irg);