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1 : : /* Information about function binary interfaces.
2 : : Copyright (C) 2019-2024 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 : : #ifndef GCC_FUNCTION_ABI_H
21 : : #define GCC_FUNCTION_ABI_H
22 : :
23 : : /* Most targets use the same ABI for all functions in a translation
24 : : unit, but some targets support interoperability between several ABIs.
25 : : Each such ABI has a unique 0-based identifier, with 0 always being
26 : : the default choice of ABI.
27 : :
28 : : NUM_ABI_IDS is the maximum number of such ABIs that GCC can handle at once.
29 : : A bitfield with this number of bits can represent any combinaion of the
30 : : supported ABIs. */
31 : : const size_t NUM_ABI_IDS = 8;
32 : :
33 : : /* Information about one of the target's predefined ABIs. */
34 : : class predefined_function_abi
35 : : {
36 : : public:
37 : : /* A target-specific identifier for this ABI. The value must be in
38 : : the range [0, NUM_ABI_IDS - 1]. */
39 : 163790047 : unsigned int id () const { return m_id; }
40 : :
41 : : /* True if this ABI has been initialized. */
42 : 17257 : bool initialized_p () const { return m_initialized; }
43 : :
44 : : /* Return true if a function call is allowed to alter every bit of
45 : : register REGNO, so that the register contains an arbitrary value
46 : : on return. If so, the register cannot hold any part of a value
47 : : that is live across a call. */
48 : : bool
49 : 7921695747 : clobbers_full_reg_p (unsigned int regno) const
50 : : {
51 : 1137279283 : return TEST_HARD_REG_BIT (m_full_reg_clobbers, regno);
52 : : }
53 : :
54 : : /* Return true if a function call is allowed to alter some or all bits
55 : : of register REGNO.
56 : :
57 : : This is true whenever clobbers_full_reg_p (REGNO) is true. It is
58 : : also true if, for example, the ABI says that a call must preserve the
59 : : low 32 or 64 bits of REGNO, but can clobber the upper bits of REGNO.
60 : : In the latter case, it is possible for REGNO to hold values that
61 : : are live across a call, provided that the value occupies only the
62 : : call-preserved part of the register. */
63 : : bool
64 : 459613601 : clobbers_at_least_part_of_reg_p (unsigned int regno) const
65 : : {
66 : 459613601 : return TEST_HARD_REG_BIT (m_full_and_partial_reg_clobbers, regno);
67 : : }
68 : :
69 : : /* Return true if a function call is allowed to clobber at least part
70 : : of (reg:MODE REGNO). If so, it is not possible for the register
71 : : as a whole to be live across a call. */
72 : : bool
73 : 47219553 : clobbers_reg_p (machine_mode mode, unsigned int regno) const
74 : : {
75 : 47219553 : return overlaps_hard_reg_set_p (m_mode_clobbers[mode], mode, regno);
76 : : }
77 : :
78 : : /* Return the set of registers that a function call is allowed to
79 : : alter completely, so that the registers contain arbitrary values
80 : : on return. This doesn't include registers that a call can only
81 : : partly clobber (as per TARGET_HARD_REGNO_CALL_PART_CLOBBERED).
82 : :
83 : : These registers cannot hold any part of a value that is live across
84 : : a call. */
85 : 253009051 : HARD_REG_SET full_reg_clobbers () const { return m_full_reg_clobbers; }
86 : :
87 : : /* Return the set of registers that a function call is allowed to alter
88 : : to some degree. For example, if an ABI says that a call must preserve
89 : : the low 32 or 64 bits of a register R, but can clobber the upper bits
90 : : of R, R would be in this set but not in full_reg_clobbers ().
91 : :
92 : : This set is a superset of full_reg_clobbers (). It is possible for a
93 : : register in full_and_partial_reg_clobbers () & ~full_reg_clobbers ()
94 : : to contain values that are live across a call, provided that the live
95 : : value only occupies the call-preserved part of the register. */
96 : : HARD_REG_SET
97 : 697050566 : full_and_partial_reg_clobbers () const
98 : : {
99 : 696268661 : return m_full_and_partial_reg_clobbers;
100 : : }
101 : :
102 : : /* Return the set of registers that cannot be used to hold a value of
103 : : mode MODE across a function call. That is:
104 : :
105 : : (reg:REGNO MODE)
106 : :
107 : : might be clobbered by a call whenever:
108 : :
109 : : overlaps_hard_reg_set (mode_clobbers (MODE), MODE, REGNO)
110 : :
111 : : In allocation terms, the registers in the returned set conflict
112 : : with any value of mode MODE that is live across a call. */
113 : : HARD_REG_SET
114 : 356486218 : mode_clobbers (machine_mode mode) const
115 : : {
116 : 356482578 : return m_mode_clobbers[mode];
117 : : }
118 : :
119 : : void initialize (unsigned int, const_hard_reg_set);
120 : : void add_full_reg_clobber (unsigned int);
121 : :
122 : : private:
123 : : unsigned int m_id : NUM_ABI_IDS;
124 : : unsigned int m_initialized : 1;
125 : : HARD_REG_SET m_full_reg_clobbers;
126 : : HARD_REG_SET m_full_and_partial_reg_clobbers;
127 : : HARD_REG_SET m_mode_clobbers[NUM_MACHINE_MODES];
128 : : };
129 : :
130 : : /* Describes either a predefined ABI or the ABI of a particular function.
131 : : In the latter case, the ABI might make use of extra function-specific
132 : : information, such as for -fipa-ra. */
133 : : class function_abi
134 : : {
135 : : public:
136 : : /* Initialize the structure for a general function with the given ABI. */
137 : 498410081 : function_abi (const predefined_function_abi &base_abi)
138 : 498410081 : : m_base_abi (&base_abi),
139 : 498410081 : m_mask (base_abi.full_and_partial_reg_clobbers ()) {}
140 : :
141 : : /* Initialize the structure for a function that has the given ABI and
142 : : that is known not to clobber registers outside MASK. */
143 : 43534174 : function_abi (const predefined_function_abi &base_abi,
144 : : const_hard_reg_set mask)
145 : 43534174 : : m_base_abi (&base_abi), m_mask (mask) {}
146 : :
147 : : /* The predefined ABI from which this ABI is derived. */
148 : 18559085 : const predefined_function_abi &base_abi () const { return *m_base_abi; }
149 : :
150 : : /* The target-specific identifier of the predefined ABI. */
151 : 147659713 : unsigned int id () const { return m_base_abi->id (); }
152 : :
153 : : /* See the corresponding predefined_function_abi functions for
154 : : details about the following functions. */
155 : :
156 : : HARD_REG_SET
157 : 123624418 : full_reg_clobbers () const
158 : : {
159 : 123624418 : return m_mask & m_base_abi->full_reg_clobbers ();
160 : : }
161 : :
162 : : HARD_REG_SET
163 : 181940166 : full_and_partial_reg_clobbers () const
164 : : {
165 : 181940166 : return m_mask & m_base_abi->full_and_partial_reg_clobbers ();
166 : : }
167 : :
168 : : HARD_REG_SET
169 : 306618043 : mode_clobbers (machine_mode mode) const
170 : : {
171 : 306618043 : return m_mask & m_base_abi->mode_clobbers (mode);
172 : : }
173 : :
174 : : bool
175 : 6784416464 : clobbers_full_reg_p (unsigned int regno) const
176 : : {
177 : 6784416464 : return (TEST_HARD_REG_BIT (m_mask, regno)
178 : 6784416464 : & m_base_abi->clobbers_full_reg_p (regno));
179 : : }
180 : :
181 : : bool
182 : 390605965 : clobbers_at_least_part_of_reg_p (unsigned int regno) const
183 : : {
184 : 390605965 : return (TEST_HARD_REG_BIT (m_mask, regno)
185 : 390605965 : & m_base_abi->clobbers_at_least_part_of_reg_p (regno));
186 : : }
187 : :
188 : : bool
189 : 209395315 : clobbers_reg_p (machine_mode mode, unsigned int regno) const
190 : : {
191 : 209395315 : return overlaps_hard_reg_set_p (mode_clobbers (mode), mode, regno);
192 : : }
193 : :
194 : : bool
195 : 17856479 : operator== (const function_abi &other) const
196 : : {
197 : 35712935 : return m_base_abi == other.m_base_abi && m_mask == other.m_mask;
198 : : }
199 : :
200 : : bool
201 : 17856479 : operator!= (const function_abi &other) const
202 : : {
203 : 17856479 : return !operator== (other);
204 : : }
205 : :
206 : : protected:
207 : : const predefined_function_abi *m_base_abi;
208 : : HARD_REG_SET m_mask;
209 : : };
210 : :
211 : : /* This class collects information about the ABIs of functions that are
212 : : called in a particular region of code. It is mostly intended to be
213 : : used as a local variable during an IR walk. */
214 : : class function_abi_aggregator
215 : : {
216 : : public:
217 : 24265307 : function_abi_aggregator () : m_abi_clobbers () {}
218 : :
219 : : /* Record that the code region calls a function with the given ABI. */
220 : : void
221 : 5711323 : note_callee_abi (const function_abi &abi)
222 : : {
223 : 5711323 : m_abi_clobbers[abi.id ()] |= abi.full_and_partial_reg_clobbers ();
224 : 5711323 : }
225 : :
226 : : HARD_REG_SET caller_save_regs (const function_abi &) const;
227 : :
228 : : private:
229 : : HARD_REG_SET m_abi_clobbers[NUM_ABI_IDS];
230 : : };
231 : :
232 : : struct target_function_abi_info
233 : : {
234 : : /* An array of all the target ABIs that are available in this
235 : : translation unit. Not all entries are used for all targets,
236 : : but the structures are relatively small, and using a fixed-size
237 : : array avoids extra indirection.
238 : :
239 : : There are various ways of getting an ABI descriptor:
240 : :
241 : : * fndecl_abi (FNDECL) is the ABI of function FNDECL.
242 : :
243 : : * fntype_abi (FNTYPE) is the ABI of a function with type FNTYPE.
244 : :
245 : : * crtl->abi is the ABI of the function that we are currently
246 : : compiling to rtl.
247 : :
248 : : * insn_callee_abi (INSN) is the ABI used by the target of call insn INSN.
249 : :
250 : : * eh_edge_abi is the "ABI" used when taking an EH edge from an
251 : : exception-throwing statement to an exception handler. Catching
252 : : exceptions from calls can be treated as an abnormal return from
253 : : those calls, and this ABI therefore describes the ABI of functions
254 : : on such an abnormal return. Statements that throw non-call
255 : : exceptions can be treated as being implicitly wrapped in a call
256 : : that has such an abnormal return.
257 : :
258 : : At present, no target needs to support more than one EH ABI.
259 : :
260 : : * function_abis[N] is the ABI with identifier N. This can be useful
261 : : when referring back to ABIs that have been collected by number in
262 : : a bitmask, such as after walking function calls in a particular
263 : : region of code.
264 : :
265 : : * default_function_abi refers specifically to the target's default
266 : : choice of ABI, regardless of which (if any) functions actually
267 : : use it. This ABI and data derived from it do *not* provide
268 : : globally conservatively-correct information, so it is only
269 : : useful in very specific circumstances. */
270 : : predefined_function_abi x_function_abis[NUM_ABI_IDS];
271 : : };
272 : :
273 : : extern target_function_abi_info default_target_function_abi_info;
274 : : #if SWITCHABLE_TARGET
275 : : extern target_function_abi_info *this_target_function_abi_info;
276 : : #else
277 : : #define this_target_function_abi_info (&default_target_function_abi_info)
278 : : #endif
279 : :
280 : : /* See the comment above x_function_abis for when these macros should be used.
281 : : At present, eh_edge_abi is always the default ABI, but that could change
282 : : in future if a target needs it to. */
283 : : #define function_abis \
284 : : (this_target_function_abi_info->x_function_abis)
285 : : #define default_function_abi \
286 : : (this_target_function_abi_info->x_function_abis[0])
287 : : #define eh_edge_abi default_function_abi
288 : :
289 : : extern HARD_REG_SET call_clobbers_in_region (unsigned int, const_hard_reg_set,
290 : : machine_mode mode);
291 : :
292 : : /* Return true if (reg:MODE REGNO) might be clobbered by one of the
293 : : calls in a region described by ABIS and MASK, where:
294 : :
295 : : * Bit ID of ABIS is set if the region contains a call with
296 : : function_abi identifier ID.
297 : :
298 : : * MASK contains all the registers that are fully or partially
299 : : clobbered by calls in the region.
300 : :
301 : : This is not quite as accurate as testing each individual call,
302 : : but it's a close and conservatively-correct approximation.
303 : : It's much better for some targets than:
304 : :
305 : : overlaps_hard_reg_set_p (MASK, MODE, REGNO). */
306 : :
307 : : inline bool
308 : 64827600 : call_clobbered_in_region_p (unsigned int abis, const_hard_reg_set mask,
309 : : machine_mode mode, unsigned int regno)
310 : : {
311 : 64827600 : HARD_REG_SET clobbers = call_clobbers_in_region (abis, mask, mode);
312 : 64827600 : return overlaps_hard_reg_set_p (clobbers, mode, regno);
313 : : }
314 : :
315 : : extern const predefined_function_abi &fntype_abi (const_tree);
316 : : extern function_abi fndecl_abi (const_tree);
317 : : extern function_abi insn_callee_abi (const rtx_insn *);
318 : : extern function_abi expr_callee_abi (const_tree);
319 : :
320 : : #endif
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