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comparison gcc/config/mips/frame-header-opt.c @ 111:04ced10e8804

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gcc 7
author kono
date Fri, 27 Oct 2017 22:46:09 +0900
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children 84e7813d76e9
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68:561a7518be6b 111:04ced10e8804
1 /* Analyze functions to determine if callers need to allocate a frame header
2 on the stack. The frame header is used by callees to save their arguments.
3 This optimization is specific to TARGET_OLDABI targets. For TARGET_NEWABI
4 targets, if a frame header is required, it is allocated by the callee.
5
6
7 Copyright (C) 2015-2017 Free Software Foundation, Inc.
8
9 This file is part of GCC.
10
11 GCC is free software; you can redistribute it and/or modify it
12 under the terms of the GNU General Public License as published by the
13 Free Software Foundation; either version 3, or (at your option) any
14 later version.
15
16 GCC is distributed in the hope that it will be useful, but WITHOUT
17 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
18 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
19 for more details.
20
21 You should have received a copy of the GNU General Public License
22 along with GCC; see the file COPYING3. If not see
23 <http://www.gnu.org/licenses/>. */
24
25
26 #include "config.h"
27 #include "system.h"
28 #include "context.h"
29 #include "coretypes.h"
30 #include "tree.h"
31 #include "tree-core.h"
32 #include "tree-pass.h"
33 #include "target.h"
34 #include "target-globals.h"
35 #include "profile-count.h"
36 #include "cfg.h"
37 #include "cgraph.h"
38 #include "function.h"
39 #include "basic-block.h"
40 #include "gimple.h"
41 #include "gimple-iterator.h"
42 #include "gimple-walk.h"
43
44 static unsigned int frame_header_opt (void);
45
46 namespace {
47
48 const pass_data pass_data_ipa_frame_header_opt =
49 {
50 IPA_PASS, /* type */
51 "frame-header-opt", /* name */
52 OPTGROUP_NONE, /* optinfo_flags */
53 TV_CGRAPHOPT, /* tv_id */
54 0, /* properties_required */
55 0, /* properties_provided */
56 0, /* properties_destroyed */
57 0, /* todo_flags_start */
58 0, /* todo_flags_finish */
59 };
60
61 class pass_ipa_frame_header_opt : public ipa_opt_pass_d
62 {
63 public:
64 pass_ipa_frame_header_opt (gcc::context *ctxt)
65 : ipa_opt_pass_d (pass_data_ipa_frame_header_opt, ctxt,
66 NULL, /* generate_summary */
67 NULL, /* write_summary */
68 NULL, /* read_summary */
69 NULL, /* write_optimization_summary */
70 NULL, /* read_optimization_summary */
71 NULL, /* stmt_fixup */
72 0, /* function_transform_todo_flags_start */
73 NULL, /* function_transform */
74 NULL) /* variable_transform */
75 {}
76
77 /* opt_pass methods: */
78 virtual bool gate (function *)
79 {
80 /* This optimization has no affect if TARGET_NEWABI. If optimize
81 is not at least 1 then the data needed for the optimization is
82 not available and nothing will be done anyway. */
83 return TARGET_OLDABI && flag_frame_header_optimization && optimize > 0;
84 }
85
86 virtual unsigned int execute (function *) { return frame_header_opt (); }
87
88 }; // class pass_ipa_frame_header_opt
89
90 } // anon namespace
91
92 static ipa_opt_pass_d *
93 make_pass_ipa_frame_header_opt (gcc::context *ctxt)
94 {
95 return new pass_ipa_frame_header_opt (ctxt);
96 }
97
98 void
99 mips_register_frame_header_opt (void)
100 {
101 opt_pass *p = make_pass_ipa_frame_header_opt (g);
102 static struct register_pass_info f =
103 {p, "comdats", 1, PASS_POS_INSERT_AFTER };
104 register_pass (&f);
105 }
106
107
108 /* Return true if it is certain that this is a leaf function. False if it is
109 not a leaf function or if it is impossible to tell. */
110
111 static bool
112 is_leaf_function (function *fn)
113 {
114 basic_block bb;
115 gimple_stmt_iterator gsi;
116
117 /* If we do not have a cfg for this function be conservative and assume
118 it is not a leaf function. */
119 if (fn->cfg == NULL)
120 return false;
121
122 FOR_EACH_BB_FN (bb, fn)
123 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
124 if (is_gimple_call (gsi_stmt (gsi)))
125 return false;
126 return true;
127 }
128
129 /* Return true if this function has inline assembly code or if we cannot
130 be certain that it does not. False if we know that there is no inline
131 assembly. */
132
133 static bool
134 has_inlined_assembly (function *fn)
135 {
136 basic_block bb;
137 gimple_stmt_iterator gsi;
138
139 /* If we do not have a cfg for this function be conservative and assume
140 it is may have inline assembly. */
141 if (fn->cfg == NULL)
142 return true;
143
144 FOR_EACH_BB_FN (bb, fn)
145 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
146 if (gimple_code (gsi_stmt (gsi)) == GIMPLE_ASM)
147 return true;
148
149 return false;
150 }
151
152 /* Return true if this function will use the stack space allocated by its
153 caller or if we cannot determine for certain that it does not. */
154
155 static bool
156 needs_frame_header_p (function *fn)
157 {
158 tree t;
159
160 if (fn->decl == NULL)
161 return true;
162
163 if (fn->stdarg)
164 return true;
165
166 for (t = DECL_ARGUMENTS (fn->decl); t; t = TREE_CHAIN (t))
167 {
168 if (!use_register_for_decl (t))
169 return true;
170
171 /* Some 64-bit types may get copied to general registers using the frame
172 header, see mips_output_64bit_xfer. Checking for SImode only may be
173 overly restrictive but it is guaranteed to be safe. */
174 if (DECL_MODE (t) != SImode)
175 return true;
176 }
177
178 return false;
179 }
180
181 /* Return true if the argument stack space allocated by function FN is used.
182 Return false if the space is needed or if the need for the space cannot
183 be determined. */
184
185 static bool
186 callees_functions_use_frame_header (function *fn)
187 {
188 basic_block bb;
189 gimple_stmt_iterator gsi;
190 gimple *stmt;
191 tree called_fn_tree;
192 function *called_fn;
193
194 if (fn->cfg == NULL)
195 return true;
196
197 FOR_EACH_BB_FN (bb, fn)
198 {
199 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
200 {
201 stmt = gsi_stmt (gsi);
202 if (is_gimple_call (stmt))
203 {
204 called_fn_tree = gimple_call_fndecl (stmt);
205 if (called_fn_tree != NULL)
206 {
207 called_fn = DECL_STRUCT_FUNCTION (called_fn_tree);
208 if (called_fn == NULL
209 || DECL_WEAK (called_fn_tree)
210 || has_inlined_assembly (called_fn)
211 || !is_leaf_function (called_fn)
212 || !called_fn->machine->does_not_use_frame_header)
213 return true;
214 }
215 else
216 return true;
217 }
218 }
219 }
220 return false;
221 }
222
223 /* Set the callers_may_not_allocate_frame flag for any function which
224 function FN calls because FN may not allocate a frame header. */
225
226 static void
227 set_callers_may_not_allocate_frame (function *fn)
228 {
229 basic_block bb;
230 gimple_stmt_iterator gsi;
231 gimple *stmt;
232 tree called_fn_tree;
233 function *called_fn;
234
235 if (fn->cfg == NULL)
236 return;
237
238 FOR_EACH_BB_FN (bb, fn)
239 {
240 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
241 {
242 stmt = gsi_stmt (gsi);
243 if (is_gimple_call (stmt))
244 {
245 called_fn_tree = gimple_call_fndecl (stmt);
246 if (called_fn_tree != NULL)
247 {
248 called_fn = DECL_STRUCT_FUNCTION (called_fn_tree);
249 if (called_fn != NULL)
250 called_fn->machine->callers_may_not_allocate_frame = true;
251 }
252 }
253 }
254 }
255 return;
256 }
257
258 /* Scan each function to determine those that need its frame headers. Perform
259 a second scan to determine if the allocation can be skipped because none of
260 their callees require the frame header. */
261
262 static unsigned int
263 frame_header_opt ()
264 {
265 struct cgraph_node *node;
266 function *fn;
267
268 FOR_EACH_DEFINED_FUNCTION (node)
269 {
270 fn = node->get_fun ();
271 if (fn != NULL)
272 fn->machine->does_not_use_frame_header = !needs_frame_header_p (fn);
273 }
274
275 FOR_EACH_DEFINED_FUNCTION (node)
276 {
277 fn = node->get_fun ();
278 if (fn != NULL)
279 fn->machine->optimize_call_stack
280 = !callees_functions_use_frame_header (fn) && !is_leaf_function (fn);
281 }
282
283 FOR_EACH_DEFINED_FUNCTION (node)
284 {
285 fn = node->get_fun ();
286 if (fn != NULL && fn->machine->optimize_call_stack)
287 set_callers_may_not_allocate_frame (fn);
288 }
289
290 return 0;
291 }