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b8698a0f | 1 | /* Discover if the stack pointer is modified in a function. |
23a5b65a | 2 | Copyright (C) 2007-2014 Free Software Foundation, Inc. |
6fb5fa3c DB |
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 | |
9dcd6f09 | 8 | Software Foundation; either version 3, or (at your option) any later |
6fb5fa3c DB |
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 | |
9dcd6f09 NC |
17 | along with GCC; see the file COPYING3. If not see |
18 | <http://www.gnu.org/licenses/>. */ | |
6fb5fa3c DB |
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 "output.h" | |
32 | #include "df.h" | |
33 | ||
34 | /* Determine if the stack pointer is constant over the life of the function. | |
35 | Only useful before prologues have been emitted. */ | |
36 | ||
37 | static void | |
7bc980e1 | 38 | notice_stack_pointer_modification_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED, |
6fb5fa3c DB |
39 | void *data ATTRIBUTE_UNUSED) |
40 | { | |
41 | if (x == stack_pointer_rtx | |
42 | /* The stack pointer is only modified indirectly as the result | |
43 | of a push until later. See the comments in rtl.texi | |
44 | regarding Embedded Side-Effects on Addresses. */ | |
45 | || (MEM_P (x) | |
46 | && GET_RTX_CLASS (GET_CODE (XEXP (x, 0))) == RTX_AUTOINC | |
47 | && XEXP (XEXP (x, 0), 0) == stack_pointer_rtx)) | |
416ff32e | 48 | crtl->sp_is_unchanging = 0; |
6fb5fa3c DB |
49 | } |
50 | ||
6fb5fa3c DB |
51 | /* Some targets can emit simpler epilogues if they know that sp was |
52 | not ever modified during the function. After reload, of course, | |
53 | we've already emitted the epilogue so there's no sense searching. */ | |
54 | ||
27a4cd48 DM |
55 | namespace { |
56 | ||
57 | const pass_data pass_data_stack_ptr_mod = | |
6fb5fa3c | 58 | { |
27a4cd48 DM |
59 | RTL_PASS, /* type */ |
60 | "*stack_ptr_mod", /* name */ | |
61 | OPTGROUP_NONE, /* optinfo_flags */ | |
27a4cd48 DM |
62 | TV_NONE, /* tv_id */ |
63 | 0, /* properties_required */ | |
64 | 0, /* properties_provided */ | |
65 | 0, /* properties_destroyed */ | |
66 | 0, /* todo_flags_start */ | |
67 | 0, /* todo_flags_finish */ | |
6fb5fa3c | 68 | }; |
27a4cd48 DM |
69 | |
70 | class pass_stack_ptr_mod : public rtl_opt_pass | |
71 | { | |
72 | public: | |
c3284718 RS |
73 | pass_stack_ptr_mod (gcc::context *ctxt) |
74 | : rtl_opt_pass (pass_data_stack_ptr_mod, ctxt) | |
27a4cd48 DM |
75 | {} |
76 | ||
77 | /* opt_pass methods: */ | |
be55bfe6 | 78 | virtual unsigned int execute (function *); |
27a4cd48 DM |
79 | |
80 | }; // class pass_stack_ptr_mod | |
81 | ||
be55bfe6 TS |
82 | unsigned int |
83 | pass_stack_ptr_mod::execute (function *fun) | |
84 | { | |
85 | basic_block bb; | |
21f110ce | 86 | rtx_insn *insn; |
be55bfe6 TS |
87 | |
88 | /* Assume that the stack pointer is unchanging if alloca hasn't | |
89 | been used. */ | |
90 | crtl->sp_is_unchanging = !fun->calls_alloca; | |
91 | if (crtl->sp_is_unchanging) | |
92 | FOR_EACH_BB_FN (bb, fun) | |
93 | FOR_BB_INSNS (bb, insn) | |
94 | { | |
95 | if (INSN_P (insn)) | |
96 | { | |
97 | /* Check if insn modifies the stack pointer. */ | |
98 | note_stores (PATTERN (insn), | |
99 | notice_stack_pointer_modification_1, | |
100 | NULL); | |
101 | if (! crtl->sp_is_unchanging) | |
102 | return 0; | |
103 | } | |
104 | } | |
105 | ||
106 | /* The value coming into this pass was 0, and the exit block uses | |
107 | are based on this. If the value is now 1, we need to redo the | |
108 | exit block uses. */ | |
109 | if (df && crtl->sp_is_unchanging) | |
110 | df_update_exit_block_uses (); | |
111 | ||
112 | return 0; | |
113 | } | |
114 | ||
27a4cd48 DM |
115 | } // anon namespace |
116 | ||
117 | rtl_opt_pass * | |
118 | make_pass_stack_ptr_mod (gcc::context *ctxt) | |
119 | { | |
120 | return new pass_stack_ptr_mod (ctxt); | |
121 | } |