nsz Git - libfirm/blob - ir/be/beflags.c

   1 /*
   2  * This file is part of libFirm.
   3  * Copyright (C) 2012 University of Karlsruhe.
   4  */
   5
   6 /**
   7  * @file
   8  * @brief       modifies schedule so flags dependencies are respected.
   9  * @author      Matthias Braun, Christoph Mallon
  10  *
  11  * Fixup schedule to respect flag constraints by moving and rematerialisation of
  12  * nodes.
  13  *
  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.
  18  *
  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.
  22  */
  23 #include "config.h"
  24
  25 #include <stdbool.h>
  26
  27 #include "irgwalk.h"
  28 #include "irnode_t.h"
  29 #include "irtools.h"
  30 #include "ircons.h"
  31 #include "iredges_t.h"
  32 #include "irprintf.h"
  33 #include "error.h"
  34
  35 #include "beflags.h"
  36 #include "bearch.h"
  37 #include "beirg.h"
  38 #include "beirgmod.h"
  39 #include "besched.h"
  40 #include "benode.h"
  41 #include "belive.h"
  42 #include "beabihelper.h"
  43
  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;
  48 static int                          changed;
  49
  50 static ir_node *default_remat(ir_node *node, ir_node *after)
  51 {
  52         ir_node *block, *copy;
  53         if (is_Block(after))
  54                 block = after;
  55         else
  56                 block = get_nodes_block(after);
  57
  58         copy = exact_copy(node);
  59         set_nodes_block(copy, block);
  60         sched_add_after(after, copy);
  61
  62         return copy;
  63 }
  64
  65 static bool default_check_modifies(const ir_node *node)
  66 {
  67         return arch_irn_is(node, modify_flags);
  68 }
  69
  70 /**
  71  * tests whether we can legally move node node after node after
  72  * (only works for nodes in same block)
  73  */
  74 static bool can_move(ir_node *node, ir_node *after)
  75 {
  76         ir_node *node_block = get_nodes_block(node);
  77         assert(node_block == get_nodes_block(after));
  78
  79         /* TODO respect dep edges */
  80         assert(get_irn_n_edges_kind(node, EDGE_KIND_DEP) == 0);
  81
  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);
  85                 if (is_Proj(out)) {
  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)
  90                                         continue;
  91                                 /* Phi or End represents a usage at block end. */
  92                                 if (is_Phi(out2) || is_End(out2))
  93                                         continue;
  94                                 if (is_Sync(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))
  99                                                         continue;
 100                                                 assert(!is_Sync(out3));
 101                                                 if (sched_get_time_step(out3) <= sched_get_time_step(after)) {
 102                                                         return false;
 103                                                 }
 104                                         }
 105                                 } else if (sched_get_time_step(out2) <= sched_get_time_step(after)) {
 106                                         return false;
 107                                 }
 108                         }
 109                 } else {
 110                         if (get_nodes_block(out) != node_block)
 111                                 continue;
 112                         /* phi represents a usage at block end */
 113                         if (is_Phi(out))
 114                                 continue;
 115                         if (sched_get_time_step(out) <= sched_get_time_step(after)) {
 116                                 return false;
 117                         }
 118                 }
 119         }
 120
 121         return true;
 122 }
 123
 124 static void rematerialize_or_move(ir_node *flags_needed, ir_node *node,
 125                                   ir_node *flag_consumers, int pn)
 126 {
 127         ir_node *n;
 128         ir_node *copy;
 129         ir_node *value;
 130
 131         if (!is_Block(node) &&
 132                         get_nodes_block(flags_needed) == get_nodes_block(node) &&
 133                         can_move(flags_needed, node)) {
 134                 /* move it */
 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 */
 138                 return;
 139         }
 140
 141         changed = 1;
 142         copy    = remat(flags_needed, node);
 143
 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);
 148         } else {
 149                 value = copy;
 150         }
 151
 152         n = flag_consumers;
 153         do {
 154                 int i;
 155                 int arity = get_irn_arity(n);
 156                 for (i = 0; i < arity; ++i) {
 157                         ir_node *in = get_irn_n(n, i);
 158                         in = skip_Proj(in);
 159                         if (in == flags_needed) {
 160                                 set_irn_n(n, i, value);
 161                                 break;
 162                         }
 163                 }
 164                 n = (ir_node*)get_irn_link(n);
 165         } while (n != NULL);
 166
 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);
 173                 int       i;
 174
 175                 if (lv != NULL) {
 176                         for (i = get_irn_arity(copy) - 1; i >= 0; --i) {
 177                                 be_liveness_update(lv, get_irn_n(copy, i));
 178                         }
 179                 }
 180         }
 181 }
 182
 183 /**
 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)
 189  */
 190 static void fix_flags_walker(ir_node *block, void *env)
 191 {
 192         ir_node *flags_needed   = NULL;
 193         ir_node *flag_consumers = NULL;
 194         int      pn = -1;
 195         (void) env;
 196
 197         ir_node *place = block;
 198         sched_foreach_reverse(block, node) {
 199                 int i, arity;
 200                 ir_node *new_flags_needed = NULL;
 201                 ir_node *test;
 202
 203                 if (is_Phi(node)) {
 204                         place = node;
 205                         break;
 206                 }
 207
 208                 if (node == flags_needed) {
 209                         /* all ok */
 210                         flags_needed   = NULL;
 211                         flag_consumers = NULL;
 212                 }
 213
 214                 /* test whether node destroys the flags */
 215                 test = node;
 216                 if (be_is_Keep(test))
 217                         test = sched_prev(test);
 218
 219                 if (flags_needed != NULL && check_modify(test)) {
 220                         /* rematerialize */
 221                         rematerialize_or_move(flags_needed, node, flag_consumers, pn);
 222                         flags_needed   = NULL;
 223                         flag_consumers = NULL;
 224                 }
 225
 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);
 234                         }
 235                 }
 236
 237                 if (new_flags_needed == NULL)
 238                         continue;
 239
 240                 /* spiller can't (correctly) remat flag consumers at the moment */
 241                 assert(!arch_irn_is(node, rematerializable));
 242
 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);
 247                                 flags_needed   = NULL;
 248                                 flag_consumers = NULL;
 249                         }
 250
 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);
 256                         }
 257                         flag_consumers = node;
 258                         set_irn_link(flag_consumers, NULL);
 259                         assert(arch_irn_is(flags_needed, rematerializable));
 260                 } else {
 261                         /* link all consumers in a list */
 262                         set_irn_link(node, flag_consumers);
 263                         flag_consumers = node;
 264                 }
 265         }
 266
 267         if (flags_needed != NULL) {
 268                 assert(get_nodes_block(flags_needed) != block);
 269                 rematerialize_or_move(flags_needed, place, flag_consumers, pn);
 270                 flags_needed   = NULL;
 271                 flag_consumers = NULL;
 272         }
 273
 274         assert(flags_needed   == NULL);
 275         assert(flag_consumers == NULL);
 276 }
 277
 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)
 281 {
 282         flag_class   = flag_cls;
 283         flags_reg    = & flag_class->regs[0];
 284         remat        = remat_func;
 285         check_modify = check_modifies_flags_func;
 286         changed      = 0;
 287         if (remat == NULL)
 288                 remat = &default_remat;
 289         if (check_modify == NULL)
 290                 check_modify = &default_check_modifies;
 291
 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);
 295
 296         if (changed) {
 297                 be_remove_dead_nodes_from_schedule(irg);
 298         }
 299 }