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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"
55 static const arch_env_t *arch_env = NULL;
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;
60 static ir_node *default_remat(ir_node *node, ir_node *after)
62 ir_node *block, *copy;
66 block = get_nodes_block(after);
68 copy = exact_copy(node);
69 set_nodes_block(copy, block);
70 sched_add_after(after, copy);
76 * tests wether we can legally move node node after node after
77 * (only works for nodes in same block)
79 static int can_move(ir_node *node, ir_node *after)
81 const ir_edge_t *edge;
82 assert(get_nodes_block(node) == get_nodes_block(after));
84 /* TODO respect dep edges */
85 assert(get_irn_n_edges_kind(node, EDGE_KIND_DEP) == 0);
87 /** all users have to be after the after node */
88 foreach_out_edge(node, edge) {
89 ir_node *out = get_edge_src_irn(edge);
91 const ir_edge_t *edge2;
92 assert(get_irn_n_edges_kind(out, EDGE_KIND_DEP) == 0);
93 foreach_out_edge(out, edge2) {
94 ir_node *out2 = get_edge_src_irn(edge2);
95 /* phi represents a usage at block end */
98 if(sched_get_time_step(out2) <= sched_get_time_step(after)) {
103 /* phi represents a usage at block end */
106 if(sched_get_time_step(out) <= sched_get_time_step(after)) {
115 static void rematerialize_or_move(ir_node *flags_needed, ir_node *node,
116 ir_node *flag_consumers, int pn)
122 if(!is_Block(node) &&
123 get_nodes_block(flags_needed) == get_nodes_block(node) &&
124 can_move(flags_needed, node)) {
126 sched_remove(flags_needed);
127 sched_add_after(node, flags_needed);
128 ir_fprintf(stderr, "Move node %+F after node %+F\n", flags_needed, node);
132 copy = remat(flags_needed, node);
133 ir_fprintf(stderr, "Remat node %+F after node %+F\n", flags_needed, node);
135 if(get_irn_mode(copy) == mode_T) {
136 ir_node *block = get_nodes_block(copy);
137 ir_mode *mode = flag_class->mode;
138 value = new_rd_Proj(NULL, current_ir_graph, block,
147 int arity = get_irn_arity(n);
148 for(i = 0; i < arity; ++i) {
149 ir_node *in = get_irn_n(n, i);
151 if(in == flags_needed) {
152 set_irn_n(n, i, value);
161 * walks up the schedule and makes sure there are no flag-destroying nodes
162 * between a flag-consumer -> flag-producer chain. Fixes problematic situations
163 * by moving and/or rematerialisation of the flag-producers.
164 * (This can be extended in the future to do some register allocation on targets
165 * like ppc32 where we conceptually have 8 flag registers)
167 static void fix_flags_walker(ir_node *block, void *env)
170 ir_node *flags_needed = NULL;
171 ir_node *flag_consumers = NULL;
175 sched_foreach_reverse(block, node) {
177 ir_node *new_flags_needed = NULL;
179 if(node == flags_needed) {
182 flag_consumers = NULL;
185 /* test wether node destroys the flags */
186 if(flags_needed != NULL && arch_irn_is(arch_env, node, modify_flags)) {
188 rematerialize_or_move(flags_needed, node, flag_consumers, pn);
190 flag_consumers = NULL;
193 /* test wether the current node needs flags */
194 arity = get_irn_arity(node);
195 for(i = 0; i < arity; ++i) {
196 //ir_node *in = get_irn_n(node, i);
197 const arch_register_class_t *cls
198 = arch_get_irn_reg_class(arch_env, node, i);
199 if(cls == flag_class) {
200 assert(new_flags_needed == NULL);
201 new_flags_needed = get_irn_n(node, i);
205 if(new_flags_needed == NULL)
208 /* spiller can't (correctly) remat flag consumers at the moment */
209 assert(!arch_irn_is(arch_env, node, rematerializable));
210 if(new_flags_needed != flags_needed) {
211 if(flags_needed != NULL) {
212 /* rematerialize node */
213 rematerialize_or_move(flags_needed, node, flag_consumers, pn);
215 flag_consumers = NULL;
218 flags_needed = new_flags_needed;
219 arch_set_irn_register(arch_env, flags_needed, flags_reg);
220 if(is_Proj(flags_needed)) {
221 pn = get_Proj_proj(flags_needed);
222 flags_needed = get_Proj_pred(flags_needed);
224 flag_consumers = node;
225 set_irn_link(flag_consumers, NULL);
226 assert(arch_irn_is(arch_env, flags_needed, rematerializable));
228 /* link all consumers in a list */
229 set_irn_link(flag_consumers, node);
230 flag_consumers = node;
234 if(flags_needed != NULL) {
235 assert(get_nodes_block(flags_needed) != block);
236 rematerialize_or_move(flags_needed, block, flag_consumers, pn);
238 flag_consumers = NULL;
241 assert(flags_needed == NULL);
242 assert(flag_consumers == NULL);
245 void be_sched_fix_flags(be_irg_t *birg, const arch_register_class_t *flag_cls,
246 func_rematerialize remat_func)
248 ir_graph *irg = be_get_birg_irg(birg);
250 arch_env = be_get_birg_arch_env(birg);
251 flag_class = flag_cls;
252 flags_reg = & flag_class->regs[0];
255 remat = &default_remat;
257 set_using_irn_link(irg);
258 irg_block_walk_graph(irg, fix_flags_walker, NULL, NULL);
259 clear_using_irn_link(irg);