2 * This file is part of libFirm.
3 * Copyright (C) 2012 University of Karlsruhe.
8 * @brief modifies schedule so flags dependencies are respected.
9 * @author Matthias Braun, Christoph Mallon
11 * Fixup schedule to respect flag constraints by moving and rematerialisation of
14 * Flags are modeled as register classes with ignore registers. However to avoid
15 * bloating the graph, only flag-consumer -> producer dependencies are
16 * explicitely modeled in the graph. Nodes that just change the flags are only
17 * marked with the arch_irn_flags_modify_flags flag.
19 * Flags are usually a limited resource that can't (or at least shouldn't) be
20 * spilled. So in some situations (for example 2 adc-nodes that use the flags of
21 * a single add node on x86) operations have to be repeated to work correctly.
31 #include "iredges_t.h"
42 #include "beabihelper.h"
44 static const arch_register_class_t *flag_class;
45 static const arch_register_t *flags_reg;
46 static func_rematerialize remat;
47 static check_modifies_flags check_modify;
50 static ir_node *default_remat(ir_node *node, ir_node *after)
52 ir_node *block, *copy;
56 block = get_nodes_block(after);
58 copy = exact_copy(node);
59 set_nodes_block(copy, block);
60 sched_add_after(after, copy);
65 static bool default_check_modifies(const ir_node *node)
67 return arch_irn_is(node, modify_flags);
71 * tests whether we can legally move node node after node after
72 * (only works for nodes in same block)
74 static bool can_move(ir_node *node, ir_node *after)
76 ir_node *node_block = get_nodes_block(node);
77 assert(node_block == get_nodes_block(after));
79 /* TODO respect dep edges */
80 assert(get_irn_n_edges_kind(node, EDGE_KIND_DEP) == 0);
82 /** all users have to be after the after node */
83 foreach_out_edge(node, edge) {
84 ir_node *out = get_edge_src_irn(edge);
86 assert(get_irn_n_edges_kind(out, EDGE_KIND_DEP) == 0);
87 foreach_out_edge(out, edge2) {
88 ir_node *out2 = get_edge_src_irn(edge2);
89 if (get_nodes_block(out2) != node_block)
91 /* Phi or End represents a usage at block end. */
92 if (is_Phi(out2) || is_End(out2))
95 foreach_out_edge(out2, edge3) {
96 ir_node *out3 = get_edge_src_irn(edge3);
97 /* Phi or End represents a usage at block end. */
98 if (is_Phi(out3) || is_End(out3))
100 assert(!is_Sync(out3));
101 if (sched_get_time_step(out3) <= sched_get_time_step(after)) {
105 } else if (sched_get_time_step(out2) <= sched_get_time_step(after)) {
110 if (get_nodes_block(out) != node_block)
112 /* phi represents a usage at block end */
115 if (sched_get_time_step(out) <= sched_get_time_step(after)) {
124 static void rematerialize_or_move(ir_node *flags_needed, ir_node *node,
125 ir_node *flag_consumers, int pn)
131 if (!is_Block(node) &&
132 get_nodes_block(flags_needed) == get_nodes_block(node) &&
133 can_move(flags_needed, node)) {
135 sched_remove(flags_needed);
136 sched_add_after(node, flags_needed);
137 /* No need to update liveness, because the node stays in the same block */
142 copy = remat(flags_needed, node);
144 if (get_irn_mode(copy) == mode_T) {
145 ir_mode *mode = flag_class->mode;
146 value = new_rd_Proj(NULL, copy, mode, pn);
147 be_add_missing_keeps_node(copy);
155 int arity = get_irn_arity(n);
156 for (i = 0; i < arity; ++i) {
157 ir_node *in = get_irn_n(n, i);
159 if (in == flags_needed) {
160 set_irn_n(n, i, value);
164 n = (ir_node*)get_irn_link(n);
167 /* No need to introduce the copy, because it only lives in this block, but
168 * we have to update the liveness of all operands */
169 if (is_Block(node) ||
170 get_nodes_block(node) != get_nodes_block(flags_needed)) {
171 ir_graph *irg = get_irn_irg(node);
172 be_lv_t *lv = be_get_irg_liveness(irg);
176 for (i = get_irn_arity(copy) - 1; i >= 0; --i) {
177 be_liveness_update(lv, get_irn_n(copy, i));
184 * walks up the schedule and makes sure there are no flag-destroying nodes
185 * between a flag-consumer -> flag-producer chain. Fixes problematic situations
186 * by moving and/or rematerialisation of the flag-producers.
187 * (This can be extended in the future to do some register allocation on targets
188 * like ppc32 where we conceptually have 8 flag registers)
190 static void fix_flags_walker(ir_node *block, void *env)
192 ir_node *flags_needed = NULL;
193 ir_node *flag_consumers = NULL;
197 ir_node *place = block;
198 sched_foreach_reverse(block, node) {
200 ir_node *new_flags_needed = NULL;
208 if (node == flags_needed) {
211 flag_consumers = NULL;
214 /* test whether node destroys the flags */
216 if (be_is_Keep(test))
217 test = sched_prev(test);
219 if (flags_needed != NULL && check_modify(test)) {
221 rematerialize_or_move(flags_needed, node, flag_consumers, pn);
223 flag_consumers = NULL;
226 /* test whether the current node needs flags */
227 arity = get_irn_arity(node);
228 for (i = 0; i < arity; ++i) {
229 const arch_register_req_t *req
230 = arch_get_irn_register_req_in(node, i);
231 if (req->cls == flag_class) {
232 assert(new_flags_needed == NULL);
233 new_flags_needed = get_irn_n(node, i);
237 if (new_flags_needed == NULL)
240 /* spiller can't (correctly) remat flag consumers at the moment */
241 assert(!arch_irn_is(node, rematerializable));
243 if (skip_Proj(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(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(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, place, flag_consumers, pn);
271 flag_consumers = NULL;
274 assert(flags_needed == NULL);
275 assert(flag_consumers == NULL);
278 void be_sched_fix_flags(ir_graph *irg, const arch_register_class_t *flag_cls,
279 func_rematerialize remat_func,
280 check_modifies_flags check_modifies_flags_func)
282 flag_class = flag_cls;
283 flags_reg = & flag_class->regs[0];
285 check_modify = check_modifies_flags_func;
288 remat = &default_remat;
289 if (check_modify == NULL)
290 check_modify = &default_check_modifies;
292 ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK);
293 irg_block_walk_graph(irg, fix_flags_walker, NULL, NULL);
294 ir_free_resources(irg, IR_RESOURCE_IRN_LINK);
297 be_remove_dead_nodes_from_schedule(irg);