1/* Web construction code for GNU compiler. 2 Contributed by Jan Hubicka. 3 Copyright (C) 2001, 2002, 2004, 2006 4 Free Software Foundation, Inc. 5 6This file is part of GCC. 7 8GCC is free software; you can redistribute it and/or modify it under 9the terms of the GNU General Public License as published by the Free 10Software Foundation; either version 2, or (at your option) any later 11version. 12 13GCC is distributed in the hope that it will be useful, but WITHOUT ANY 14WARRANTY; without even the implied warranty of MERCHANTABILITY or 15FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 16for more details. 17 18You should have received a copy of the GNU General Public License 19along with GCC; see the file COPYING. If not, write to the Free 20Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 2102110-1301, USA. */ 22 23/* Simple optimization pass that splits independent uses of each pseudo, 24 increasing effectiveness of other optimizations. The optimization can 25 serve as an example of use for the dataflow module. 26 27 We don't split registers with REG_USERVAR set unless -fmessy-debugging 28 is specified, because debugging information about such split variables 29 is almost unusable. 30 31 TODO 32 - Add code to keep debugging up-to-date after splitting user variable 33 pseudos. This can be done by keeping track of all the pseudos used 34 for the variable and using life analysis information before reload 35 to determine which one is live and, in case more than one are live, 36 choose the one with the latest definition. 37 38 Other optimization passes can benefit from the infrastructure too. 39 40 - We may use profile information and ignore infrequent use for the 41 purpose of web unifying, inserting the compensation code later to 42 implement full induction variable expansion for loops (currently 43 we expand only if the induction variable is dead afterward, which 44 is often the case). */ 45 46#include "config.h" 47#include "system.h" 48#include "coretypes.h" 49#include "tm.h" 50#include "toplev.h" 51 52#include "rtl.h" 53#include "hard-reg-set.h" 54#include "flags.h" 55#include "obstack.h" 56#include "basic-block.h" 57#include "output.h" 58#include "df.h" 59#include "function.h" 60#include "timevar.h" 61#include "tree-pass.h" 62 63 64static rtx entry_register (struct web_entry *, struct df_ref *, char *); 65static void replace_ref (struct df_ref *, rtx); 66 67/* Find the root of unionfind tree (the representative of set). */ 68 69struct web_entry * 70unionfind_root (struct web_entry *element) 71{ 72 struct web_entry *element1 = element, *element2; 73 74 while (element->pred) 75 element = element->pred; 76 while (element1->pred) 77 { 78 element2 = element1->pred; 79 element1->pred = element; 80 element1 = element2; 81 } 82 return element; 83} 84 85/* Union sets. 86 Return true if FIRST and SECOND points to the same web entry structure and 87 nothing is done. Otherwise, return false. */ 88 89bool 90unionfind_union (struct web_entry *first, struct web_entry *second) 91{ 92 first = unionfind_root (first); 93 second = unionfind_root (second); 94 if (first == second) 95 return true; 96 second->pred = first; 97 return false; 98} 99 100/* For each use, all possible defs reaching it must come in the same 101 register, union them. 102 FUN is the function that does the union. */ 103 104void 105union_defs (struct df *df, struct df_ref *use, struct web_entry *def_entry, 106 struct web_entry *use_entry, 107 bool (*fun) (struct web_entry *, struct web_entry *)) 108{ 109 rtx insn = DF_REF_INSN (use); 110 struct df_link *link = DF_REF_CHAIN (use); 111 struct df_ref *use_link; 112 struct df_ref *def_link; 113 rtx set; 114 115 if (insn) 116 { 117 use_link = DF_INSN_USES (df, insn); 118 def_link = DF_INSN_DEFS (df, insn); 119 set = single_set (insn); 120 } 121 else 122 { 123 use_link = NULL; 124 def_link = NULL; 125 set = NULL; 126 } 127 128 /* Some instructions may use match_dup for their operands. In case the 129 operands are dead, we will assign them different pseudos, creating 130 invalid instructions, so union all uses of the same operand for each 131 insn. */ 132 133 while (use_link) 134 { 135 if (use != use_link 136 && DF_REF_REAL_REG (use) == DF_REF_REAL_REG (use_link)) 137 (*fun) (use_entry + DF_REF_ID (use), 138 use_entry + DF_REF_ID (use_link)); 139 use_link = use_link->next_ref; 140 } 141 142 /* Recognize trivial noop moves and attempt to keep them as noop. 143 While most of noop moves should be removed, we still keep some 144 of them at libcall boundaries and such. */ 145 146 if (set 147 && SET_SRC (set) == DF_REF_REG (use) 148 && SET_SRC (set) == SET_DEST (set)) 149 { 150 while (def_link) 151 { 152 if (DF_REF_REAL_REG (use) == DF_REF_REAL_REG (def_link)) 153 (*fun) (use_entry + DF_REF_ID (use), 154 def_entry + DF_REF_ID (def_link)); 155 def_link = def_link->next_ref; 156 } 157 } 158 while (link) 159 { 160 (*fun) (use_entry + DF_REF_ID (use), 161 def_entry + DF_REF_ID (link->ref)); 162 link = link->next; 163 } 164 165 /* A READ_WRITE use requires the corresponding def to be in the same 166 register. Find it and union. */ 167 if (use->flags & DF_REF_READ_WRITE) 168 { 169 struct df_ref *link; 170 171 if (DF_REF_INSN (use)) 172 link = DF_INSN_DEFS (df, DF_REF_INSN (use)); 173 else 174 link = NULL; 175 176 while (link) 177 { 178 if (DF_REF_REAL_REG (link) == DF_REF_REAL_REG (use)) 179 (*fun) (use_entry + DF_REF_ID (use), 180 def_entry + DF_REF_ID (link)); 181 link = link->next_ref; 182 } 183 } 184} 185 186/* Find the corresponding register for the given entry. */ 187 188static rtx 189entry_register (struct web_entry *entry, struct df_ref *ref, char *used) 190{ 191 struct web_entry *root; 192 rtx reg, newreg; 193 194 /* Find the corresponding web and see if it has been visited. */ 195 root = unionfind_root (entry); 196 if (root->reg) 197 return root->reg; 198 199 /* We are seeing this web for the first time, do the assignment. */ 200 reg = DF_REF_REAL_REG (ref); 201 202 /* In case the original register is already assigned, generate new one. */ 203 if (!used[REGNO (reg)]) 204 newreg = reg, used[REGNO (reg)] = 1; 205 else if (REG_USERVAR_P (reg) && 0/*&& !flag_messy_debugging*/) 206 { 207 newreg = reg; 208 if (dump_file) 209 fprintf (dump_file, 210 "New web forced to keep reg=%i (user variable)\n", 211 REGNO (reg)); 212 } 213 else 214 { 215 newreg = gen_reg_rtx (GET_MODE (reg)); 216 REG_USERVAR_P (newreg) = REG_USERVAR_P (reg); 217 REG_POINTER (newreg) = REG_POINTER (reg); 218 REG_ATTRS (newreg) = REG_ATTRS (reg); 219 if (dump_file) 220 fprintf (dump_file, "Web oldreg=%i newreg=%i\n", REGNO (reg), 221 REGNO (newreg)); 222 } 223 224 root->reg = newreg; 225 return newreg; 226} 227 228/* Replace the reference by REG. */ 229 230static void 231replace_ref (struct df_ref *ref, rtx reg) 232{ 233 rtx oldreg = DF_REF_REAL_REG (ref); 234 rtx *loc = DF_REF_REAL_LOC (ref); 235 236 if (oldreg == reg) 237 return; 238 if (dump_file) 239 fprintf (dump_file, "Updating insn %i (%i->%i)\n", 240 INSN_UID (DF_REF_INSN (ref)), REGNO (oldreg), REGNO (reg)); 241 *loc = reg; 242} 243 244/* Main entry point. */ 245 246static void 247web_main (void) 248{ 249 struct df *df; 250 struct web_entry *def_entry; 251 struct web_entry *use_entry; 252 unsigned int i; 253 int max = max_reg_num (); 254 char *used; 255 256 df = df_init (DF_EQUIV_NOTES); 257 df_chain_add_problem (df, DF_UD_CHAIN); 258 df_analyze (df); 259 df_reorganize_refs (&df->def_info); 260 df_reorganize_refs (&df->use_info); 261 262 def_entry = XCNEWVEC (struct web_entry, DF_DEFS_SIZE (df)); 263 use_entry = XCNEWVEC (struct web_entry, DF_USES_SIZE (df)); 264 used = XCNEWVEC (char, max); 265 266 if (dump_file) 267 df_dump (df, dump_file); 268 269 /* Produce the web. */ 270 for (i = 0; i < DF_USES_SIZE (df); i++) 271 union_defs (df, DF_USES_GET (df, i), def_entry, use_entry, unionfind_union); 272 273 /* Update the instruction stream, allocating new registers for split pseudos 274 in progress. */ 275 for (i = 0; i < DF_USES_SIZE (df); i++) 276 replace_ref (DF_USES_GET (df, i), 277 entry_register (use_entry + i, DF_USES_GET (df, i), used)); 278 for (i = 0; i < DF_DEFS_SIZE (df); i++) 279 replace_ref (DF_DEFS_GET (df, i), 280 entry_register (def_entry + i, DF_DEFS_GET (df, i), used)); 281 282 /* Dataflow information is corrupt here, but it can be easily updated 283 by creating new entries for new registers and updates or calling 284 df_insns_modify. */ 285 free (def_entry); 286 free (use_entry); 287 free (used); 288 df_finish (df); 289 df = NULL; 290} 291 292static bool 293gate_handle_web (void) 294{ 295 return (optimize > 0 && flag_web); 296} 297 298static unsigned int 299rest_of_handle_web (void) 300{ 301 web_main (); 302 delete_trivially_dead_insns (get_insns (), max_reg_num ()); 303 cleanup_cfg (CLEANUP_EXPENSIVE); 304 reg_scan (get_insns (), max_reg_num ()); 305 return 0; 306} 307 308struct tree_opt_pass pass_web = 309{ 310 "web", /* name */ 311 gate_handle_web, /* gate */ 312 rest_of_handle_web, /* execute */ 313 NULL, /* sub */ 314 NULL, /* next */ 315 0, /* static_pass_number */ 316 TV_WEB, /* tv_id */ 317 0, /* properties_required */ 318 0, /* properties_provided */ 319 0, /* properties_destroyed */ 320 0, /* todo_flags_start */ 321 TODO_dump_func, /* todo_flags_finish */ 322 'Z' /* letter */ 323}; 324 325