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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"
53 #include "besched_t.h"
56 static const arch_env_t *arch_env = NULL;
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 wether we can legally move node node after node after
79 * (only works for nodes in same block)
81 static int 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 represents a usage at block end */
101 const ir_edge_t *edge3;
102 foreach_out_edge(out2, edge3) {
103 ir_node *out3 = get_edge_src_irn(edge3);
104 /* phi represents a usage at block end */
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, be_lv_t *lv)
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_node *block = get_nodes_block(copy);
151 ir_mode *mode = flag_class->mode;
152 value = new_rd_Proj(NULL, current_ir_graph, block,
161 int arity = get_irn_arity(n);
162 for(i = 0; i < arity; ++i) {
163 ir_node *in = get_irn_n(n, i);
165 if(in == flags_needed) {
166 set_irn_n(n, i, value);
173 /* No need to introduce the copy, because it only lives in this block, but
174 * we have to update the liveness of all operands */
175 if (is_Block(node) ||
176 get_nodes_block(node) != get_nodes_block(flags_needed)) {
179 for (i = get_irn_arity(copy) - 1; i >= 0; --i) {
180 be_liveness_update(lv, get_irn_n(copy, i));
185 static int is_modify_flags(ir_node *node) {
188 if(arch_irn_is(arch_env, node, modify_flags))
190 if(!be_is_Keep(node))
193 arity = get_irn_arity(node);
194 for(i = 0; i < arity; ++i) {
195 ir_node *in = get_irn_n(node, i);
197 if(arch_irn_is(arch_env, in, modify_flags))
205 * walks up the schedule and makes sure there are no flag-destroying nodes
206 * between a flag-consumer -> flag-producer chain. Fixes problematic situations
207 * by moving and/or rematerialisation of the flag-producers.
208 * (This can be extended in the future to do some register allocation on targets
209 * like ppc32 where we conceptually have 8 flag registers)
211 static void fix_flags_walker(ir_node *block, void *env)
214 ir_node *flags_needed = NULL;
215 ir_node *flag_consumers = NULL;
218 sched_foreach_reverse(block, node) {
220 ir_node *new_flags_needed = NULL;
225 if(node == flags_needed) {
228 flag_consumers = NULL;
231 /* test whether node destroys the flags */
232 if(flags_needed != NULL && is_modify_flags(node)) {
234 rematerialize_or_move(flags_needed, node, flag_consumers, pn, env);
236 flag_consumers = NULL;
239 /* test whether the current node needs flags */
240 arity = get_irn_arity(node);
241 for(i = 0; i < arity; ++i) {
242 const arch_register_class_t *cls = arch_get_irn_reg_class(node, i);
243 if(cls == flag_class) {
244 assert(new_flags_needed == NULL);
245 new_flags_needed = get_irn_n(node, i);
249 if(new_flags_needed == NULL)
252 /* spiller can't (correctly) remat flag consumers at the moment */
253 assert(!arch_irn_is(arch_env, node, rematerializable));
255 if(skip_Proj(new_flags_needed) != flags_needed) {
256 if(flags_needed != NULL) {
257 /* rematerialize node */
258 rematerialize_or_move(flags_needed, node, flag_consumers, pn, env);
260 flag_consumers = NULL;
263 flags_needed = new_flags_needed;
264 arch_set_irn_register(flags_needed, flags_reg);
265 if(is_Proj(flags_needed)) {
266 pn = get_Proj_proj(flags_needed);
267 flags_needed = get_Proj_pred(flags_needed);
269 flag_consumers = node;
270 set_irn_link(flag_consumers, NULL);
271 assert(arch_irn_is(arch_env, flags_needed, rematerializable));
273 /* link all consumers in a list */
274 set_irn_link(node, flag_consumers);
275 flag_consumers = node;
279 if(flags_needed != NULL) {
280 assert(get_nodes_block(flags_needed) != block);
281 rematerialize_or_move(flags_needed, node, flag_consumers, pn, env);
283 flag_consumers = NULL;
286 assert(flags_needed == NULL);
287 assert(flag_consumers == NULL);
290 void be_sched_fix_flags(be_irg_t *birg, const arch_register_class_t *flag_cls,
291 func_rematerialize remat_func)
293 ir_graph *irg = be_get_birg_irg(birg);
295 arch_env = be_get_birg_arch_env(birg);
296 flag_class = flag_cls;
297 flags_reg = & flag_class->regs[0];
301 remat = &default_remat;
303 ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK);
304 irg_block_walk_graph(irg, fix_flags_walker, NULL, birg->lv);
305 ir_free_resources(irg, IR_RESOURCE_IRN_LINK);
308 be_remove_dead_nodes_from_schedule(birg);