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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"
57 static const arch_register_class_t *flag_class = NULL;
58 static const arch_register_t *flags_reg = NULL;
59 static func_rematerialize remat = NULL;
62 static ir_node *default_remat(ir_node *node, ir_node *after)
64 ir_node *block, *copy;
68 block = get_nodes_block(after);
70 copy = exact_copy(node);
71 set_nodes_block(copy, block);
72 sched_add_after(after, copy);
78 * tests whether we can legally move node node after node after
79 * (only works for nodes in same block)
81 static bool can_move(ir_node *node, ir_node *after)
83 const ir_edge_t *edge;
84 assert(get_nodes_block(node) == get_nodes_block(after));
86 /* TODO respect dep edges */
87 assert(get_irn_n_edges_kind(node, EDGE_KIND_DEP) == 0);
89 /** all users have to be after the after node */
90 foreach_out_edge(node, edge) {
91 ir_node *out = get_edge_src_irn(edge);
93 const ir_edge_t *edge2;
94 assert(get_irn_n_edges_kind(out, EDGE_KIND_DEP) == 0);
95 foreach_out_edge(out, edge2) {
96 ir_node *out2 = get_edge_src_irn(edge2);
97 /* Phi or End represents a usage at block end. */
98 if (is_Phi(out2) || is_End(out2))
101 const ir_edge_t *edge3;
102 foreach_out_edge(out2, edge3) {
103 ir_node *out3 = get_edge_src_irn(edge3);
104 /* Phi or End represents a usage at block end. */
105 if (is_Phi(out3) || is_End(out3))
107 assert(!is_Sync(out3));
108 if (sched_get_time_step(out3) <= sched_get_time_step(after)) {
112 } else if (sched_get_time_step(out2) <= sched_get_time_step(after)) {
117 /* phi represents a usage at block end */
120 if (sched_get_time_step(out) <= sched_get_time_step(after)) {
129 static void rematerialize_or_move(ir_node *flags_needed, ir_node *node,
130 ir_node *flag_consumers, int pn)
136 if (!is_Block(node) &&
137 get_nodes_block(flags_needed) == get_nodes_block(node) &&
138 can_move(flags_needed, node)) {
140 sched_remove(flags_needed);
141 sched_add_after(node, flags_needed);
142 /* No need to update liveness, because the node stays in the same block */
147 copy = remat(flags_needed, node);
149 if (get_irn_mode(copy) == mode_T) {
150 ir_mode *mode = flag_class->mode;
151 value = new_rd_Proj(NULL, copy, mode, pn);
159 int arity = get_irn_arity(n);
160 for (i = 0; i < arity; ++i) {
161 ir_node *in = get_irn_n(n, i);
163 if (in == flags_needed) {
164 set_irn_n(n, i, value);
171 /* No need to introduce the copy, because it only lives in this block, but
172 * we have to update the liveness of all operands */
173 if (is_Block(node) ||
174 get_nodes_block(node) != get_nodes_block(flags_needed)) {
175 ir_graph *irg = get_irn_irg(node);
176 be_lv_t *lv = be_get_irg_liveness(irg);
180 for (i = get_irn_arity(copy) - 1; i >= 0; --i) {
181 be_liveness_update(lv, get_irn_n(copy, i));
187 static bool is_modify_flags(ir_node *node)
189 return arch_irn_is(node, modify_flags);
193 * walks up the schedule and makes sure there are no flag-destroying nodes
194 * between a flag-consumer -> flag-producer chain. Fixes problematic situations
195 * by moving and/or rematerialisation of the flag-producers.
196 * (This can be extended in the future to do some register allocation on targets
197 * like ppc32 where we conceptually have 8 flag registers)
199 static void fix_flags_walker(ir_node *block, void *env)
202 ir_node *flags_needed = NULL;
203 ir_node *flag_consumers = NULL;
207 sched_foreach_reverse(block, node) {
209 ir_node *new_flags_needed = NULL;
215 if (node == flags_needed) {
218 flag_consumers = NULL;
221 /* test whether node destroys the flags */
223 if (be_is_Keep(test))
224 test = sched_prev(test);
226 if (flags_needed != NULL && is_modify_flags(test)) {
228 rematerialize_or_move(flags_needed, node, flag_consumers, pn);
230 flag_consumers = NULL;
233 /* test whether the current node needs flags */
234 arity = get_irn_arity(node);
235 for (i = 0; i < arity; ++i) {
236 const arch_register_class_t *cls = arch_get_irn_reg_class(node, i);
237 if (cls == flag_class) {
238 assert(new_flags_needed == NULL);
239 new_flags_needed = get_irn_n(node, i);
243 if (new_flags_needed == NULL)
246 /* spiller can't (correctly) remat flag consumers at the moment */
247 assert(!arch_irn_is(node, rematerializable));
249 if (skip_Proj(new_flags_needed) != flags_needed) {
250 if (flags_needed != NULL) {
251 /* rematerialize node */
252 rematerialize_or_move(flags_needed, node, flag_consumers, pn);
254 flag_consumers = NULL;
257 flags_needed = new_flags_needed;
258 arch_set_irn_register(flags_needed, flags_reg);
259 if (is_Proj(flags_needed)) {
260 pn = get_Proj_proj(flags_needed);
261 flags_needed = get_Proj_pred(flags_needed);
263 flag_consumers = node;
264 set_irn_link(flag_consumers, NULL);
265 assert(arch_irn_is(flags_needed, rematerializable));
267 /* link all consumers in a list */
268 set_irn_link(node, flag_consumers);
269 flag_consumers = node;
273 if (flags_needed != NULL) {
274 assert(get_nodes_block(flags_needed) != block);
275 rematerialize_or_move(flags_needed, node, flag_consumers, pn);
277 flag_consumers = NULL;
280 assert(flags_needed == NULL);
281 assert(flag_consumers == NULL);
284 void be_sched_fix_flags(ir_graph *irg, const arch_register_class_t *flag_cls,
285 func_rematerialize remat_func)
287 flag_class = flag_cls;
288 flags_reg = & flag_class->regs[0];
292 remat = &default_remat;
294 ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK);
295 irg_block_walk_graph(irg, fix_flags_walker, NULL, NULL);
296 ir_free_resources(irg, IR_RESOURCE_IRN_LINK);
299 be_remove_dead_nodes_from_schedule(irg);