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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_register_class_t *flag_class = NULL;
57 static const arch_register_t *flags_reg = NULL;
58 static func_rematerialize remat = NULL;
61 static ir_node *default_remat(ir_node *node, ir_node *after)
63 ir_node *block, *copy;
67 block = get_nodes_block(after);
69 copy = exact_copy(node);
70 set_nodes_block(copy, block);
71 sched_add_after(after, copy);
77 * tests wether we can legally move node node after node after
78 * (only works for nodes in same block)
80 static int can_move(ir_node *node, ir_node *after)
82 const ir_edge_t *edge;
83 assert(get_nodes_block(node) == get_nodes_block(after));
85 /* TODO respect dep edges */
86 assert(get_irn_n_edges_kind(node, EDGE_KIND_DEP) == 0);
88 /** all users have to be after the after node */
89 foreach_out_edge(node, edge) {
90 ir_node *out = get_edge_src_irn(edge);
92 const ir_edge_t *edge2;
93 assert(get_irn_n_edges_kind(out, EDGE_KIND_DEP) == 0);
94 foreach_out_edge(out, edge2) {
95 ir_node *out2 = get_edge_src_irn(edge2);
96 /* phi represents a usage at block end */
100 const ir_edge_t *edge3;
101 foreach_out_edge(out2, edge3) {
102 ir_node *out3 = get_edge_src_irn(edge3);
103 /* phi represents a usage at block end */
106 assert(!is_Sync(out3));
107 if(sched_get_time_step(out3) <= sched_get_time_step(after)) {
111 } else if(sched_get_time_step(out2) <= sched_get_time_step(after)) {
116 /* phi represents a usage at block end */
119 if(sched_get_time_step(out) <= sched_get_time_step(after)) {
128 static void rematerialize_or_move(ir_node *flags_needed, ir_node *node,
129 ir_node *flag_consumers, int pn, be_lv_t *lv)
135 if(!is_Block(node) &&
136 get_nodes_block(flags_needed) == get_nodes_block(node) &&
137 can_move(flags_needed, node)) {
139 sched_remove(flags_needed);
140 sched_add_after(node, flags_needed);
141 /* No need to update liveness, because the node stays in the same block */
146 copy = remat(flags_needed, node);
148 if(get_irn_mode(copy) == mode_T) {
149 ir_node *block = get_nodes_block(copy);
150 ir_mode *mode = flag_class->mode;
151 value = new_rd_Proj(NULL, current_ir_graph, block,
160 int arity = get_irn_arity(n);
161 for(i = 0; i < arity; ++i) {
162 ir_node *in = get_irn_n(n, i);
164 if(in == flags_needed) {
165 set_irn_n(n, i, value);
172 /* No need to introduce the copy, because it only lives in this block, but
173 * we have to update the liveness of all operands */
174 if (is_Block(node) ||
175 get_nodes_block(node) != get_nodes_block(flags_needed)) {
178 for (i = get_irn_arity(copy) - 1; i >= 0; --i) {
179 be_liveness_update(lv, get_irn_n(copy, i));
184 static int is_modify_flags(ir_node *node) {
187 if (arch_irn_is(node, modify_flags))
189 if(!be_is_Keep(node))
192 arity = get_irn_arity(node);
193 for(i = 0; i < arity; ++i) {
194 ir_node *in = get_irn_n(node, i);
196 if (arch_irn_is(in, modify_flags))
204 * walks up the schedule and makes sure there are no flag-destroying nodes
205 * between a flag-consumer -> flag-producer chain. Fixes problematic situations
206 * by moving and/or rematerialisation of the flag-producers.
207 * (This can be extended in the future to do some register allocation on targets
208 * like ppc32 where we conceptually have 8 flag registers)
210 static void fix_flags_walker(ir_node *block, void *env)
213 ir_node *flags_needed = NULL;
214 ir_node *flag_consumers = NULL;
217 sched_foreach_reverse(block, node) {
219 ir_node *new_flags_needed = NULL;
224 if(node == flags_needed) {
227 flag_consumers = NULL;
230 /* test whether node destroys the flags */
231 if(flags_needed != NULL && is_modify_flags(node)) {
233 rematerialize_or_move(flags_needed, node, flag_consumers, pn, env);
235 flag_consumers = NULL;
238 /* test whether the current node needs flags */
239 arity = get_irn_arity(node);
240 for(i = 0; i < arity; ++i) {
241 const arch_register_class_t *cls = arch_get_irn_reg_class(node, i);
242 if(cls == flag_class) {
243 assert(new_flags_needed == NULL);
244 new_flags_needed = get_irn_n(node, i);
248 if(new_flags_needed == NULL)
251 /* spiller can't (correctly) remat flag consumers at the moment */
252 assert(!arch_irn_is(node, rematerializable));
254 if(skip_Proj(new_flags_needed) != flags_needed) {
255 if(flags_needed != NULL) {
256 /* rematerialize node */
257 rematerialize_or_move(flags_needed, node, flag_consumers, pn, env);
259 flag_consumers = NULL;
262 flags_needed = new_flags_needed;
263 arch_set_irn_register(flags_needed, flags_reg);
264 if(is_Proj(flags_needed)) {
265 pn = get_Proj_proj(flags_needed);
266 flags_needed = get_Proj_pred(flags_needed);
268 flag_consumers = node;
269 set_irn_link(flag_consumers, NULL);
270 assert(arch_irn_is(flags_needed, rematerializable));
272 /* link all consumers in a list */
273 set_irn_link(node, flag_consumers);
274 flag_consumers = node;
278 if(flags_needed != NULL) {
279 assert(get_nodes_block(flags_needed) != block);
280 rematerialize_or_move(flags_needed, node, flag_consumers, pn, env);
282 flag_consumers = NULL;
285 assert(flags_needed == NULL);
286 assert(flag_consumers == NULL);
289 void be_sched_fix_flags(be_irg_t *birg, const arch_register_class_t *flag_cls,
290 func_rematerialize remat_func)
292 ir_graph *irg = be_get_birg_irg(birg);
294 flag_class = flag_cls;
295 flags_reg = & flag_class->regs[0];
299 remat = &default_remat;
301 ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK);
302 irg_block_walk_graph(irg, fix_flags_walker, NULL, birg->lv);
303 ir_free_resources(irg, IR_RESOURCE_IRN_LINK);
306 be_remove_dead_nodes_from_schedule(birg);