1/* Information about fuunction binary interfaces.
2   Copyright (C) 2019-2020 Free Software Foundation, Inc.
3
4This file is part of GCC
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 3, or (at your option) any later
9version.
10
11GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License
17along 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.  */
31const size_t NUM_ABI_IDS = 8;
32
33/* Information about one of the target's predefined ABIs.  */
34class predefined_function_abi
35{
36public:
37  /* A target-specific identifier for this ABI.  The value must be in
38     the range [0, NUM_ABI_IDS - 1].  */
39  unsigned int id () const { return m_id; }
40
41  /* True if this ABI has been initialized.  */
42  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  clobbers_full_reg_p (unsigned int regno) const
50  {
51    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  clobbers_at_least_part_of_reg_p (unsigned int regno) const
65  {
66    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  clobbers_reg_p (machine_mode mode, unsigned int regno) const
74  {
75    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  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  full_and_partial_reg_clobbers () const
98  {
99    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  mode_clobbers (machine_mode mode) const
115  {
116    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
122private:
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.  */
133class function_abi
134{
135public:
136  /* Initialize the structure for a general function with the given ABI.  */
137  function_abi (const predefined_function_abi &base_abi)
138    : m_base_abi (&base_abi),
139      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  function_abi (const predefined_function_abi &base_abi,
144		const_hard_reg_set mask)
145    : m_base_abi (&base_abi), m_mask (mask) {}
146
147  /* The predefined ABI from which this ABI is derived.  */
148  const predefined_function_abi &base_abi () const { return *m_base_abi; }
149
150  /* The target-specific identifier of the predefined ABI.  */
151  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  full_reg_clobbers () const
158  {
159    return m_mask & m_base_abi->full_reg_clobbers ();
160  }
161
162  HARD_REG_SET
163  full_and_partial_reg_clobbers () const
164  {
165    return m_mask & m_base_abi->full_and_partial_reg_clobbers ();
166  }
167
168  HARD_REG_SET
169  mode_clobbers (machine_mode mode) const
170  {
171    return m_mask & m_base_abi->mode_clobbers (mode);
172  }
173
174  bool
175  clobbers_full_reg_p (unsigned int regno) const
176  {
177    return (TEST_HARD_REG_BIT (m_mask, regno)
178	    & m_base_abi->clobbers_full_reg_p (regno));
179  }
180
181  bool
182  clobbers_at_least_part_of_reg_p (unsigned int regno) const
183  {
184    return (TEST_HARD_REG_BIT (m_mask, regno)
185	    & m_base_abi->clobbers_at_least_part_of_reg_p (regno));
186  }
187
188  bool
189  clobbers_reg_p (machine_mode mode, unsigned int regno) const
190  {
191    return overlaps_hard_reg_set_p (mode_clobbers (mode), mode, regno);
192  }
193
194  bool
195  operator== (const function_abi &other) const
196  {
197    return m_base_abi == other.m_base_abi && m_mask == other.m_mask;
198  }
199
200  bool
201  operator!= (const function_abi &other) const
202  {
203    return !operator== (other);
204  }
205
206protected:
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.  */
214class function_abi_aggregator
215{
216public:
217  function_abi_aggregator () : m_abi_clobbers () {}
218
219  /* Record that the code region calls a function with the given ABI.  */
220  void
221  note_callee_abi (const function_abi &abi)
222  {
223    m_abi_clobbers[abi.id ()] |= abi.full_and_partial_reg_clobbers ();
224  }
225
226  HARD_REG_SET caller_save_regs (const function_abi &) const;
227
228private:
229  HARD_REG_SET m_abi_clobbers[NUM_ABI_IDS];
230};
231
232struct 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
273extern target_function_abi_info default_target_function_abi_info;
274#if SWITCHABLE_TARGET
275extern 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
289extern 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
307inline bool
308call_clobbered_in_region_p (unsigned int abis, const_hard_reg_set mask,
309			    machine_mode mode, unsigned int regno)
310{
311  HARD_REG_SET clobbers = call_clobbers_in_region (abis, mask, mode);
312  return overlaps_hard_reg_set_p (clobbers, mode, regno);
313}
314
315extern const predefined_function_abi &fntype_abi (const_tree);
316extern function_abi fndecl_abi (const_tree);
317extern function_abi insn_callee_abi (const rtx_insn *);
318extern function_abi expr_callee_abi (const_tree);
319
320#endif
321