1 /* Web construction code for GNU compiler.
2 Contributed by Jan Hubicka.
3 Copyright (C) 2001, 2002, 2004 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
22 /* Simple optimization pass that splits independent uses of each pseudo,
23 increasing effectiveness of other optimizations. The optimization can
24 serve as an example of use for the dataflow module.
26 We don't split registers with REG_USERVAR set unless -fmessy-debugging
27 is specified, because debugging information about such split variables
31 - Add code to keep debugging up-to-date after splitting user variable
32 pseudos. This can be done by keeping track of all the pseudos used
33 for the variable and using life analysis information before reload
34 to determine which one is live and, in case more than one are live,
35 choose the one with the latest definition.
37 Other optimization passes can benefit from the infrastructure too.
39 - We may use profile information and ignore infrequent use for the
40 purpose of web unifying, inserting the compensation code later to
41 implement full induction variable expansion for loops (currently
42 we expand only if the induction variable is dead afterward, which
43 is often the case). */
47 #include "coretypes.h"
52 #include "hard-reg-set.h"
54 #include "basic-block.h"
60 /* This entry is allocated for each reference in the insn stream. */
63 /* Pointer to the parent in the union/find tree. */
64 struct web_entry
*pred
;
65 /* Newly assigned register to the entry. Set only for roots. */
69 static struct web_entry
*unionfind_root (struct web_entry
*);
70 static void unionfind_union (struct web_entry
*, struct web_entry
*);
71 static void union_defs (struct df
*, struct ref
*, struct web_entry
*,
73 static rtx
entry_register (struct web_entry
*, struct ref
*, char *, char *);
74 static void replace_ref (struct ref
*, rtx
);
75 static int mark_addressof (rtx
*, void *);
77 /* Find the root of unionfind tree (the representative of set). */
79 static struct web_entry
*
80 unionfind_root (struct web_entry
*element
)
82 struct web_entry
*element1
= element
, *element2
;
85 element
= element
->pred
;
86 while (element1
->pred
)
88 element2
= element1
->pred
;
89 element1
->pred
= element
;
98 unionfind_union (struct web_entry
*first
, struct web_entry
*second
)
100 first
= unionfind_root (first
);
101 second
= unionfind_root (second
);
104 second
->pred
= first
;
107 /* For each use, all possible defs reaching it must come in the same
108 register, union them. */
111 union_defs (struct df
*df
, struct ref
*use
, struct web_entry
*def_entry
,
112 struct web_entry
*use_entry
)
114 rtx insn
= DF_REF_INSN (use
);
115 struct df_link
*link
= DF_REF_CHAIN (use
);
116 struct df_link
*use_link
= DF_INSN_USES (df
, insn
);
117 struct df_link
*def_link
= DF_INSN_DEFS (df
, insn
);
118 rtx set
= single_set (insn
);
120 /* Some instructions may use match_dup for their operands. In case the
121 operands are dead, we will assign them different pseudos, creating
122 invalid instructions, so union all uses of the same operand for each
127 if (use
!= use_link
->ref
128 && DF_REF_REAL_REG (use
) == DF_REF_REAL_REG (use_link
->ref
))
129 unionfind_union (use_entry
+ DF_REF_ID (use
),
130 use_entry
+ DF_REF_ID (use_link
->ref
));
131 use_link
= use_link
->next
;
134 /* Recognize trivial noop moves and attempt to keep them as noop.
135 While most of noop moves should be removed, we still keep some
136 of them at libcall boundaries and such. */
139 && SET_SRC (set
) == DF_REF_REG (use
)
140 && SET_SRC (set
) == SET_DEST (set
))
144 if (DF_REF_REAL_REG (use
) == DF_REF_REAL_REG (def_link
->ref
))
145 unionfind_union (use_entry
+ DF_REF_ID (use
),
146 def_entry
+ DF_REF_ID (def_link
->ref
));
147 def_link
= def_link
->next
;
152 unionfind_union (use_entry
+ DF_REF_ID (use
),
153 def_entry
+ DF_REF_ID (link
->ref
));
157 /* A READ_WRITE use requires the corresponding def to be in the same
158 register. Find it and union. */
159 if (use
->flags
& DF_REF_READ_WRITE
)
161 struct df_link
*link
= DF_INSN_DEFS (df
, DF_REF_INSN (use
));
163 while (DF_REF_REAL_REG (link
->ref
) != DF_REF_REAL_REG (use
))
166 unionfind_union (use_entry
+ DF_REF_ID (use
),
167 def_entry
+ DF_REF_ID (link
->ref
));
171 /* Find the corresponding register for the given entry. */
174 entry_register (struct web_entry
*entry
, struct ref
*ref
, char *used
,
177 struct web_entry
*root
;
180 /* Find the corresponding web and see if it has been visited. */
181 root
= unionfind_root (entry
);
185 /* We are seeing this web for the first time, do the assignment. */
186 reg
= DF_REF_REAL_REG (ref
);
188 /* In case the original register is already assigned, generate new one. */
189 if (!used
[REGNO (reg
)])
190 newreg
= reg
, used
[REGNO (reg
)] = 1;
191 else if (REG_USERVAR_P (reg
) && 0/*&& !flag_messy_debugging*/)
196 "New web forced to keep reg=%i (user variable)\n",
199 else if (use_addressof
[REGNO (reg
)])
204 "New web forced to keep reg=%i (address taken)\n",
209 newreg
= gen_reg_rtx (GET_MODE (reg
));
210 REG_USERVAR_P (newreg
) = REG_USERVAR_P (reg
);
211 REG_POINTER (newreg
) = REG_POINTER (reg
);
212 REG_LOOP_TEST_P (newreg
) = REG_LOOP_TEST_P (reg
);
213 RTX_UNCHANGING_P (newreg
) = RTX_UNCHANGING_P (reg
);
214 REG_ATTRS (newreg
) = REG_ATTRS (reg
);
216 fprintf (dump_file
, "Web oldreg=%i newreg=%i\n", REGNO (reg
),
224 /* Replace the reference by REG. */
227 replace_ref (struct ref
*ref
, rtx reg
)
229 rtx oldreg
= DF_REF_REAL_REG (ref
);
230 rtx
*loc
= DF_REF_REAL_LOC (ref
);
235 fprintf (dump_file
, "Updating insn %i (%i->%i)\n",
236 INSN_UID (DF_REF_INSN (ref
)), REGNO (oldreg
), REGNO (reg
));
240 /* Mark each pseudo whose address is taken. */
243 mark_addressof (rtx
*rtl
, void *data
)
247 if (GET_CODE (*rtl
) == ADDRESSOF
248 && REG_P (XEXP (*rtl
, 0)))
249 ((char *)data
)[REGNO (XEXP (*rtl
, 0))] = 1;
253 /* Main entry point. */
259 struct web_entry
*def_entry
;
260 struct web_entry
*use_entry
;
262 int max
= max_reg_num ();
268 df_analyze (df
, 0, DF_UD_CHAIN
| DF_EQUIV_NOTES
);
271 (struct web_entry
*) xcalloc (df
->n_defs
, sizeof (struct web_entry
));
273 (struct web_entry
*) xcalloc (df
->n_uses
, sizeof (struct web_entry
));
274 used
= (char *) xcalloc (max
, sizeof (char));
275 use_addressof
= (char *) xcalloc (max
, sizeof (char));
278 df_dump (df
, DF_UD_CHAIN
| DF_DU_CHAIN
, dump_file
);
280 /* Produce the web. */
281 for (i
= 0; i
< df
->n_uses
; i
++)
282 union_defs (df
, df
->uses
[i
], def_entry
, use_entry
);
284 /* We can not safely rename registers whose address is taken. */
285 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
287 for_each_rtx (&PATTERN (insn
), mark_addressof
, use_addressof
);
289 /* Update the instruction stream, allocating new registers for split pseudos
291 for (i
= 0; i
< df
->n_uses
; i
++)
292 replace_ref (df
->uses
[i
], entry_register (use_entry
+ i
, df
->uses
[i
],
293 used
, use_addressof
));
294 for (i
= 0; i
< df
->n_defs
; i
++)
295 replace_ref (df
->defs
[i
], entry_register (def_entry
+ i
, df
->defs
[i
],
296 used
, use_addressof
));
298 /* Dataflow information is corrupt here, but it can be easily updated
299 by creating new entries for new registers and updates or calling
304 free (use_addressof
);