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[/] [openrisc/] [trunk/] [gnu-src/] [gcc-4.2.2/] [gcc/] [web.c] - Rev 165
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/* Web construction code for GNU compiler. Contributed by Jan Hubicka. Copyright (C) 2001, 2002, 2004, 2006, 2007 Free Software Foundation, Inc. This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see <http://www.gnu.org/licenses/>. */ /* Simple optimization pass that splits independent uses of each pseudo, increasing effectiveness of other optimizations. The optimization can serve as an example of use for the dataflow module. We don't split registers with REG_USERVAR set unless -fmessy-debugging is specified, because debugging information about such split variables is almost unusable. TODO - Add code to keep debugging up-to-date after splitting user variable pseudos. This can be done by keeping track of all the pseudos used for the variable and using life analysis information before reload to determine which one is live and, in case more than one are live, choose the one with the latest definition. Other optimization passes can benefit from the infrastructure too. - We may use profile information and ignore infrequent use for the purpose of web unifying, inserting the compensation code later to implement full induction variable expansion for loops (currently we expand only if the induction variable is dead afterward, which is often the case). */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "toplev.h" #include "rtl.h" #include "hard-reg-set.h" #include "flags.h" #include "obstack.h" #include "basic-block.h" #include "output.h" #include "df.h" #include "function.h" #include "timevar.h" #include "tree-pass.h" static rtx entry_register (struct web_entry *, struct df_ref *, char *); static void replace_ref (struct df_ref *, rtx); /* Find the root of unionfind tree (the representative of set). */ struct web_entry * unionfind_root (struct web_entry *element) { struct web_entry *element1 = element, *element2; while (element->pred) element = element->pred; while (element1->pred) { element2 = element1->pred; element1->pred = element; element1 = element2; } return element; } /* Union sets. Return true if FIRST and SECOND points to the same web entry structure and nothing is done. Otherwise, return false. */ bool unionfind_union (struct web_entry *first, struct web_entry *second) { first = unionfind_root (first); second = unionfind_root (second); if (first == second) return true; second->pred = first; return false; } /* For each use, all possible defs reaching it must come in the same register, union them. FUN is the function that does the union. */ void union_defs (struct df *df, struct df_ref *use, struct web_entry *def_entry, struct web_entry *use_entry, bool (*fun) (struct web_entry *, struct web_entry *)) { rtx insn = DF_REF_INSN (use); struct df_link *link = DF_REF_CHAIN (use); struct df_ref *use_link; struct df_ref *def_link; rtx set; if (insn) { use_link = DF_INSN_USES (df, insn); def_link = DF_INSN_DEFS (df, insn); set = single_set (insn); } else { use_link = NULL; def_link = NULL; set = NULL; } /* Some instructions may use match_dup for their operands. In case the operands are dead, we will assign them different pseudos, creating invalid instructions, so union all uses of the same operand for each insn. */ while (use_link) { if (use != use_link && DF_REF_REAL_REG (use) == DF_REF_REAL_REG (use_link)) (*fun) (use_entry + DF_REF_ID (use), use_entry + DF_REF_ID (use_link)); use_link = use_link->next_ref; } /* Recognize trivial noop moves and attempt to keep them as noop. While most of noop moves should be removed, we still keep some of them at libcall boundaries and such. */ if (set && SET_SRC (set) == DF_REF_REG (use) && SET_SRC (set) == SET_DEST (set)) { while (def_link) { if (DF_REF_REAL_REG (use) == DF_REF_REAL_REG (def_link)) (*fun) (use_entry + DF_REF_ID (use), def_entry + DF_REF_ID (def_link)); def_link = def_link->next_ref; } } while (link) { (*fun) (use_entry + DF_REF_ID (use), def_entry + DF_REF_ID (link->ref)); link = link->next; } /* A READ_WRITE use requires the corresponding def to be in the same register. Find it and union. */ if (use->flags & DF_REF_READ_WRITE) { struct df_ref *link; if (DF_REF_INSN (use)) link = DF_INSN_DEFS (df, DF_REF_INSN (use)); else link = NULL; while (link) { if (DF_REF_REAL_REG (link) == DF_REF_REAL_REG (use)) (*fun) (use_entry + DF_REF_ID (use), def_entry + DF_REF_ID (link)); link = link->next_ref; } } } /* Find the corresponding register for the given entry. */ static rtx entry_register (struct web_entry *entry, struct df_ref *ref, char *used) { struct web_entry *root; rtx reg, newreg; /* Find the corresponding web and see if it has been visited. */ root = unionfind_root (entry); if (root->reg) return root->reg; /* We are seeing this web for the first time, do the assignment. */ reg = DF_REF_REAL_REG (ref); /* In case the original register is already assigned, generate new one. */ if (!used[REGNO (reg)]) newreg = reg, used[REGNO (reg)] = 1; else if (REG_USERVAR_P (reg) && 0/*&& !flag_messy_debugging*/) { newreg = reg; if (dump_file) fprintf (dump_file, "New web forced to keep reg=%i (user variable)\n", REGNO (reg)); } else { newreg = gen_reg_rtx (GET_MODE (reg)); REG_USERVAR_P (newreg) = REG_USERVAR_P (reg); REG_POINTER (newreg) = REG_POINTER (reg); REG_ATTRS (newreg) = REG_ATTRS (reg); if (dump_file) fprintf (dump_file, "Web oldreg=%i newreg=%i\n", REGNO (reg), REGNO (newreg)); } root->reg = newreg; return newreg; } /* Replace the reference by REG. */ static void replace_ref (struct df_ref *ref, rtx reg) { rtx oldreg = DF_REF_REAL_REG (ref); rtx *loc = DF_REF_REAL_LOC (ref); if (oldreg == reg) return; if (dump_file) fprintf (dump_file, "Updating insn %i (%i->%i)\n", INSN_UID (DF_REF_INSN (ref)), REGNO (oldreg), REGNO (reg)); *loc = reg; } /* Main entry point. */ static void web_main (void) { struct df *df; struct web_entry *def_entry; struct web_entry *use_entry; unsigned int i; int max = max_reg_num (); char *used; df = df_init (DF_EQUIV_NOTES); df_chain_add_problem (df, DF_UD_CHAIN); df_analyze (df); df_reorganize_refs (&df->def_info); df_reorganize_refs (&df->use_info); def_entry = XCNEWVEC (struct web_entry, DF_DEFS_SIZE (df)); use_entry = XCNEWVEC (struct web_entry, DF_USES_SIZE (df)); used = XCNEWVEC (char, max); if (dump_file) df_dump (df, dump_file); /* Produce the web. */ for (i = 0; i < DF_USES_SIZE (df); i++) union_defs (df, DF_USES_GET (df, i), def_entry, use_entry, unionfind_union); /* Update the instruction stream, allocating new registers for split pseudos in progress. */ for (i = 0; i < DF_USES_SIZE (df); i++) replace_ref (DF_USES_GET (df, i), entry_register (use_entry + i, DF_USES_GET (df, i), used)); for (i = 0; i < DF_DEFS_SIZE (df); i++) replace_ref (DF_DEFS_GET (df, i), entry_register (def_entry + i, DF_DEFS_GET (df, i), used)); /* Dataflow information is corrupt here, but it can be easily updated by creating new entries for new registers and updates or calling df_insns_modify. */ free (def_entry); free (use_entry); free (used); df_finish (df); df = NULL; } static bool gate_handle_web (void) { return (optimize > 0 && flag_web); } static unsigned int rest_of_handle_web (void) { web_main (); delete_trivially_dead_insns (get_insns (), max_reg_num ()); cleanup_cfg (CLEANUP_EXPENSIVE); reg_scan (get_insns (), max_reg_num ()); return 0; } struct tree_opt_pass pass_web = { "web", /* name */ gate_handle_web, /* gate */ rest_of_handle_web, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ TV_WEB, /* tv_id */ 0, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ TODO_dump_func, /* todo_flags_finish */ 'Z' /* letter */ };
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