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comparison gcc/init-regs.c @ 0:a06113de4d67

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author kent <kent@cr.ie.u-ryukyu.ac.jp>
date Fri, 17 Jul 2009 14:47:48 +0900
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children 77e2b8dfacca
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-1:000000000000 0:a06113de4d67
1 /* Initialization of uninitialized regs.
2 Copyright (C) 2007, 2008 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
9 version.
10
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
19
20 #include "config.h"
21 #include "system.h"
22 #include "coretypes.h"
23 #include "tm.h"
24 #include "tree.h"
25 #include "rtl.h"
26 #include "regs.h"
27 #include "expr.h"
28 #include "tree-pass.h"
29 #include "basic-block.h"
30 #include "flags.h"
31 #include "df.h"
32
33 /* Check all of the uses of pseudo variables. If any use that is MUST
34 uninitialized, add a store of 0 immediately before it. For
35 subregs, this makes combine happy. For full word regs, this makes
36 other optimizations, like the register allocator and the reg-stack
37 happy as well as papers over some problems on the arm and other
38 processors where certain isa constraints cannot be handled by gcc.
39 These are of the form where two operands to an insn my not be the
40 same. The ra will only make them the same if they do not
41 interfere, and this can only happen if one is not initialized.
42
43 There is also the unfortunate consequence that this may mask some
44 buggy programs where people forget to initialize stack variable.
45 Any programmer with half a brain would look at the uninitialized
46 variable warnings. */
47
48 static void
49 initialize_uninitialized_regs (void)
50 {
51 basic_block bb;
52 bitmap already_genned = BITMAP_ALLOC (NULL);
53
54 if (optimize == 1)
55 {
56 df_live_add_problem ();
57 df_live_set_all_dirty ();
58 }
59
60 df_analyze ();
61
62 FOR_EACH_BB (bb)
63 {
64 rtx insn;
65 bitmap lr = DF_LR_IN (bb);
66 bitmap ur = DF_LIVE_IN (bb);
67 bitmap_clear (already_genned);
68
69 FOR_BB_INSNS (bb, insn)
70 {
71 unsigned int uid = INSN_UID (insn);
72 df_ref *use_rec;
73 if (!INSN_P (insn))
74 continue;
75
76 for (use_rec = DF_INSN_UID_USES (uid); *use_rec; use_rec++)
77 {
78 df_ref use = *use_rec;
79 unsigned int regno = DF_REF_REGNO (use);
80
81 /* Only do this for the pseudos. */
82 if (regno < FIRST_PSEUDO_REGISTER)
83 continue;
84
85 /* Do not generate multiple moves for the same regno.
86 This is common for sequences of subreg operations.
87 They would be deleted during combine but there is no
88 reason to churn the system. */
89 if (bitmap_bit_p (already_genned, regno))
90 continue;
91
92 /* A use is MUST uninitialized if it reaches the top of
93 the block from the inside of the block (the lr test)
94 and no def for it reaches the top of the block from
95 outside of the block (the ur test). */
96 if (bitmap_bit_p (lr, regno)
97 && (!bitmap_bit_p (ur, regno)))
98 {
99 rtx move_insn;
100 rtx reg = DF_REF_REAL_REG (use);
101
102 bitmap_set_bit (already_genned, regno);
103
104 start_sequence ();
105 emit_move_insn (reg, CONST0_RTX (GET_MODE (reg)));
106 move_insn = get_insns ();
107 end_sequence ();
108 emit_insn_before (move_insn, insn);
109 if (dump_file)
110 fprintf (dump_file,
111 "adding initialization in %s of reg %d at in block %d for insn %d.\n",
112 current_function_name (), regno, bb->index, uid);
113 }
114 }
115 }
116 }
117
118 if (optimize == 1)
119 {
120 if (dump_file)
121 df_dump (dump_file);
122 df_remove_problem (df_live);
123 }
124
125 BITMAP_FREE (already_genned);
126 }
127
128 static bool
129 gate_initialize_regs (void)
130 {
131 return optimize > 0;
132 }
133
134 static unsigned int
135 rest_of_handle_initialize_regs (void)
136 {
137 initialize_uninitialized_regs ();
138 return 0;
139 }
140
141 struct rtl_opt_pass pass_initialize_regs =
142 {
143 {
144 RTL_PASS,
145 "init-regs", /* name */
146 gate_initialize_regs, /* gate */
147 rest_of_handle_initialize_regs, /* execute */
148 NULL, /* sub */
149 NULL, /* next */
150 0, /* static_pass_number */
151 0, /* tv_id */
152 0, /* properties_required */
153 0, /* properties_provided */
154 0, /* properties_destroyed */
155 0, /* todo_flags_start */
156 TODO_dump_func |
157 TODO_df_finish /* todo_flags_finish */
158 }
159 };