Daily bump.
[official-gcc.git] / gcc / init-regs.c
blobb835de07513fd3302f36c7909790e49853a21ce0
1 /* Initialization of uninitialized regs.
2 Copyright (C) 2007 Free Software Foundation,
3 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 3, or (at your option) any later
10 version.
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
15 for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
21 #include "config.h"
22 #include "system.h"
23 #include "coretypes.h"
24 #include "tm.h"
25 #include "tree.h"
26 #include "rtl.h"
27 #include "regs.h"
28 #include "expr.h"
29 #include "tree-pass.h"
30 #include "basic-block.h"
31 #include "flags.h"
32 #include "df.h"
34 /* Check all of the uses of pseudo variables. If any use that is MUST
35 uninitialized, add a store of 0 immediately before it. For
36 subregs, this makes combine happy. For full word regs, this makes
37 other optimizations, like the register allocator and the reg-stack
38 happy as well as papers over some problems on the arm and other
39 processors where certain isa constraints cannot be handled by gcc.
40 These are of the form where two operands to an insn my not be the
41 same. The ra will only make them the same if they do not
42 interfere, and this can only happen if one is not initialized.
44 There is also the unfortunate consequence that this may mask some
45 buggy programs where people forget to initialize stack variable.
46 Any programmer with half a brain would look at the uninitialized
47 variable warnings. */
49 static void
50 initialize_uninitialized_regs (void)
52 basic_block bb;
53 bitmap already_genned = BITMAP_ALLOC (NULL);
55 if (optimize == 1)
57 df_live_add_problem ();
58 df_live_set_all_dirty ();
61 df_analyze ();
63 FOR_EACH_BB (bb)
65 rtx insn;
66 bitmap lr = DF_LR_IN (bb);
67 bitmap ur = DF_LIVE_IN (bb);
68 bitmap_clear (already_genned);
70 FOR_BB_INSNS (bb, insn)
72 unsigned int uid = INSN_UID (insn);
73 struct df_ref **use_rec;
74 if (!INSN_P (insn))
75 continue;
77 for (use_rec = DF_INSN_UID_USES (uid); *use_rec; use_rec++)
79 struct df_ref *use = *use_rec;
80 unsigned int regno = DF_REF_REGNO (use);
82 /* Only do this for the pseudos. */
83 if (regno < FIRST_PSEUDO_REGISTER)
84 continue;
86 /* Do not generate multiple moves for the same regno.
87 This is common for sequences of subreg operations.
88 They would be deleted during combine but there is no
89 reason to churn the system. */
90 if (bitmap_bit_p (already_genned, regno))
91 continue;
93 /* A use is MUST uninitialized if it reaches the top of
94 the block from the inside of the block (the lr test)
95 and no def for it reaches the top of the block from
96 outside of the block (the ur test). */
97 if (bitmap_bit_p (lr, regno)
98 && (!bitmap_bit_p (ur, regno)))
100 rtx move_insn;
101 rtx reg = DF_REF_REAL_REG (use);
103 bitmap_set_bit (already_genned, regno);
105 start_sequence ();
106 emit_move_insn (reg, CONST0_RTX (GET_MODE (reg)));
107 move_insn = get_insns ();
108 end_sequence ();
109 emit_insn_before (move_insn, insn);
110 if (dump_file)
111 fprintf (dump_file,
112 "adding initialization in %s of reg %d at in block %d for insn %d.\n",
113 current_function_name (), regno, bb->index, uid);
119 if (optimize == 1)
121 if (dump_file)
122 df_dump (dump_file);
123 df_remove_problem (df_live);
126 BITMAP_FREE (already_genned);
129 static bool
130 gate_initialize_regs (void)
132 return optimize > 0;
135 static unsigned int
136 rest_of_handle_initialize_regs (void)
138 initialize_uninitialized_regs ();
139 return 0;
142 struct tree_opt_pass pass_initialize_regs =
144 "init-regs", /* name */
145 gate_initialize_regs, /* gate */
146 rest_of_handle_initialize_regs, /* execute */
147 NULL, /* sub */
148 NULL, /* next */
149 0, /* static_pass_number */
150 0, /* tv_id */
151 0, /* properties_required */
152 0, /* properties_provided */
153 0, /* properties_destroyed */
154 0, /* todo_flags_start */
155 TODO_dump_func |
156 TODO_df_finish, /* todo_flags_finish */
157 0 /* letter */