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+/* Web construction code for GNU compiler.
+ Contributed by Jan Hubicka.
+ Copyright (C) 2001, 2002, 2004, 2006
+ 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 2, 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 COPYING. If not, write to the Free
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA. */
+
+/* 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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