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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;
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)
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);
144 copy = remat(flags_needed, node);
146 if(get_irn_mode(copy) == mode_T) {
147 ir_node *block = get_nodes_block(copy);
148 ir_mode *mode = flag_class->mode;
149 value = new_rd_Proj(NULL, current_ir_graph, block,
158 int arity = get_irn_arity(n);
159 for(i = 0; i < arity; ++i) {
160 ir_node *in = get_irn_n(n, i);
162 if(in == flags_needed) {
163 set_irn_n(n, i, value);
171 static int is_modify_flags(ir_node *node) {
174 if(arch_irn_is(arch_env, node, modify_flags))
176 if(!be_is_Keep(node))
179 arity = get_irn_arity(node);
180 for(i = 0; i < arity; ++i) {
181 ir_node *in = get_irn_n(node, i);
183 if(arch_irn_is(arch_env, in, modify_flags))
191 * walks up the schedule and makes sure there are no flag-destroying nodes
192 * between a flag-consumer -> flag-producer chain. Fixes problematic situations
193 * by moving and/or rematerialisation of the flag-producers.
194 * (This can be extended in the future to do some register allocation on targets
195 * like ppc32 where we conceptually have 8 flag registers)
197 static void fix_flags_walker(ir_node *block, void *env)
200 ir_node *flags_needed = NULL;
201 ir_node *flag_consumers = NULL;
205 sched_foreach_reverse(block, node) {
207 ir_node *new_flags_needed = NULL;
212 if(node == flags_needed) {
215 flag_consumers = NULL;
218 /* test wether node destroys the flags */
219 if(flags_needed != NULL && is_modify_flags(node)) {
221 rematerialize_or_move(flags_needed, node, flag_consumers, pn);
223 flag_consumers = NULL;
226 /* test wether the current node needs flags */
227 arity = get_irn_arity(node);
228 for(i = 0; i < arity; ++i) {
229 //ir_node *in = get_irn_n(node, i);
230 const arch_register_class_t *cls
231 = arch_get_irn_reg_class(arch_env, node, i);
232 if(cls == flag_class) {
233 assert(new_flags_needed == NULL);
234 new_flags_needed = get_irn_n(node, i);
238 if(new_flags_needed == NULL)
241 /* spiller can't (correctly) remat flag consumers at the moment */
242 assert(!arch_irn_is(arch_env, node, rematerializable));
243 if(new_flags_needed != flags_needed) {
244 if(flags_needed != NULL) {
245 /* rematerialize node */
246 rematerialize_or_move(flags_needed, node, flag_consumers, pn);
248 flag_consumers = NULL;
251 flags_needed = new_flags_needed;
252 arch_set_irn_register(arch_env, flags_needed, flags_reg);
253 if(is_Proj(flags_needed)) {
254 pn = get_Proj_proj(flags_needed);
255 flags_needed = get_Proj_pred(flags_needed);
257 flag_consumers = node;
258 set_irn_link(flag_consumers, NULL);
259 assert(arch_irn_is(arch_env, flags_needed, rematerializable));
261 /* link all consumers in a list */
262 set_irn_link(node, flag_consumers);
263 flag_consumers = node;
267 if(flags_needed != NULL) {
268 assert(get_nodes_block(flags_needed) != block);
269 rematerialize_or_move(flags_needed, node, flag_consumers, pn);
271 flag_consumers = NULL;
274 assert(flags_needed == NULL);
275 assert(flag_consumers == NULL);
278 void be_sched_fix_flags(be_irg_t *birg, const arch_register_class_t *flag_cls,
279 func_rematerialize remat_func)
281 ir_graph *irg = be_get_birg_irg(birg);
283 arch_env = be_get_birg_arch_env(birg);
284 flag_class = flag_cls;
285 flags_reg = & flag_class->regs[0];
288 remat = &default_remat;
290 set_using_irn_link(irg);
291 irg_block_walk_graph(irg, fix_flags_walker, NULL, NULL);
292 clear_using_irn_link(irg);