1 // Function-related RTL SSA classes -*- C++ -*-
2 // Copyright (C) 2020-2023 Free Software Foundation, Inc.
4 // This file is part of GCC.
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
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
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/>.
22 // SSA-related information about a function. It contains three levels
23 // of information, each in reverse postorder:
25 // - a list of extended basic blocks
26 // - a list of basic blocks
27 // - a list of instructions
29 // It also maintains a list of definitions of memory, and a list of
30 // definitions of each register.
32 // See doc/rtl.texi for more details about the way this information
33 // is organized and how changes to it are made.
36 // The default obstack alignment takes long double into account.
37 // Since we have no use for that here, and since we allocate many
38 // relatively small objects, it's better to specify an alignment
39 // explicitly. The allocation routines assert that the alignment
40 // is enough for the objects being allocated.
42 // Because various structures use pointer_mux, we need at least 2 bytes
44 static const size_t obstack_alignment
= sizeof (void *);
47 // Construct SSA form for function FN.
48 function_info (function
*fn
);
51 // Return a list of all the extended basic blocks in the function, in reverse
52 // postorder. The list includes the entry and exit blocks.
53 iterator_range
<ebb_iterator
> ebbs () const;
55 // Like ebbs (), but in the reverse order.
56 iterator_range
<reverse_ebb_iterator
> reverse_ebbs () const;
58 // Return a list of all the basic blocks in the function, in reverse
59 // postorder. The list includes the entry and exit blocks.
60 iterator_range
<bb_iterator
> bbs () const;
62 // Like bbs (), but in the reverse order.
63 iterator_range
<reverse_bb_iterator
> reverse_bbs () const;
65 // Return the SSA information for the basic block with index INDEX.
66 bb_info
*bb (unsigned int index
) const { return m_bbs
[index
]; }
68 // Return the SSA information for CFG_BB.
69 bb_info
*bb (basic_block cfg_bb
) const { return m_bbs
[cfg_bb
->index
]; }
71 // Create a temporary def.
72 set_info
*create_set (obstack_watermark
&watermark
,
74 resource_info resource
);
76 // Create a temporary insn with code INSN_CODE and pattern PAT.
77 insn_info
*create_insn (obstack_watermark
&watermark
,
81 // Return a list of all the instructions in the function, in reverse
82 // postorder. The list includes both real and artificial instructions.
84 // Iterations over the list will pick up any new instructions that are
85 // inserted after the iterator's current instruction.
86 iterator_range
<any_insn_iterator
> all_insns () const;
88 // Like all_insns (), but in the reverse order.
90 // Iterations over the list will pick up any new instructions that are
91 // inserted before the iterator's current instruction.
92 iterator_range
<reverse_any_insn_iterator
> reverse_all_insns () const;
94 // Like all_insns (), but without the debug instructions.
95 iterator_range
<nondebug_insn_iterator
> nondebug_insns () const;
97 // Like reverse_all_insns (), but without the debug instructions.
98 iterator_range
<reverse_nondebug_insn_iterator
>
99 reverse_nondebug_insns () const;
101 // Return the first and last instructions in insns ().
102 insn_info
*first_insn () const { return m_first_insn
; }
103 insn_info
*last_insn () const { return m_last_insn
; }
105 // Return a list of all definitions of memory, in reverse postorder.
106 // This includes both real stores by instructions and artificial
107 // definitions by things like phi nodes.
108 iterator_range
<def_iterator
> mem_defs () const;
110 // Return a list of all definitions of register REGNO, in reverse postorder.
111 // This includes both real stores by instructions and artificial
112 // definitions by things like phi nodes.
113 iterator_range
<def_iterator
> reg_defs (unsigned int regno
) const;
115 // Return true if SET is the only set of SET->resource () and if it
116 // dominates all uses (excluding uses of SET->resource () at points
117 // where SET->resource () is always undefined).
118 bool is_single_dominating_def (const set_info
*set
) const;
120 // Check if all uses of register REGNO are either unconditionally undefined
121 // or use the same single dominating definition. Return the definition
122 // if so, otherwise return null.
123 set_info
*single_dominating_def (unsigned int regno
) const;
125 // Look for a definition of RESOURCE at INSN. Return the result of the
126 // search as a def_lookup; see the comments there for more details.
127 def_lookup
find_def (resource_info resource
, insn_info
*insn
);
129 // Return an RAII object that owns all temporary RTL SSA memory
130 // allocated during a change attempt. The object should remain in
131 // scope until the change has been aborted or successfully completed.
132 obstack_watermark
new_change_attempt () { return &m_temp_obstack
; }
134 // SET and INSN belong to the same EBB, with SET occuring before INSN.
135 // Return true if SET is still available at INSN.
136 bool remains_available_at_insn (const set_info
*set
, insn_info
*insn
);
138 // SET either occurs in BB or is known to be available on entry to BB.
139 // Return true if it is also available on exit from BB. (The value
140 // might or might not be live.)
141 bool remains_available_on_exit (const set_info
*set
, bb_info
*bb
);
143 // Make a best attempt to check whether the values used by USES are
144 // available on entry to BB, without solving a full dataflow problem.
145 // If all the values are already live on entry to BB or can be made
146 // available there, return a use_array that describes the uses as
147 // if they occured at the start of BB. These uses are purely temporary,
148 // and will not become permanent unless applied using change_insns.
150 // If the operation fails, return an invalid use_array.
152 // WATERMARK is a watermark returned by new_change_attempt ().
153 // WILL_BE_DEBUG_USES is true if the returned use_array will be
154 // used only for debug instructions.
155 use_array
make_uses_available (obstack_watermark
&watermark
,
156 use_array uses
, bb_info
*bb
,
157 bool will_be_debug_uses
);
159 // If CHANGE doesn't already clobber REGNO, try to add such a clobber,
160 // limiting the movement range in order to make the clobber valid.
161 // When determining whether REGNO is live, ignore accesses made by an
162 // instruction I if IGNORE (I) is true. The caller then assumes the
163 // responsibility of ensuring that CHANGE and I are placed in a valid order.
165 // Return true on success. Leave CHANGE unmodified when returning false.
167 // WATERMARK is a watermark returned by new_change_attempt ().
168 template<typename IgnorePredicate
>
169 bool add_regno_clobber (obstack_watermark
&watermark
, insn_change
&change
,
170 unsigned int regno
, IgnorePredicate ignore
);
172 // Return true if change_insns will be able to perform the changes
173 // described by CHANGES.
174 bool verify_insn_changes (array_slice
<insn_change
*const> changes
);
176 // Perform all the changes in CHANGES, keeping the instructions in the
177 // order specified by the CHANGES array. On return, the SSA information
178 // remains up-to-date. The same is true for instruction-level DF
179 // information, although the block-level DF information might be
181 void change_insns (array_slice
<insn_change
*> changes
);
183 // Like change_insns, but for a single change CHANGE.
184 void change_insn (insn_change
&change
);
186 // Given a use USE, re-parent it to get its def from NEW_DEF.
187 void reparent_use (use_info
*use
, set_info
*new_def
);
189 // If the changes that have been made to instructions require updates
190 // to the CFG, perform those updates now. Return true if something changed.
193 // - The SSA information is now invalid and needs to be recomputed.
195 // - Dominance information is no longer available (in either direction).
197 // - The caller will need to call cleanup_cfg at some point.
199 // ??? We could probably update the SSA information for simple updates,
200 // but currently nothing would benefit. These late CFG changes are
201 // relatively rare anyway, since gimple optimisers should remove most
202 // unnecessary control flow.
203 bool perform_pending_updates ();
205 // Print the contents of the function to PP.
206 void print (pretty_printer
*pp
) const;
208 // Allocate an object of type T above the obstack watermark WM.
209 template<typename T
, typename
... Ts
>
210 T
*change_alloc (obstack_watermark
&wm
, Ts
... args
);
217 // Return an RAII object that owns all objects allocated by
218 // allocate_temp during its lifetime.
219 obstack_watermark
temp_watermark () { return &m_temp_obstack
; }
221 template<typename T
, typename
... Ts
>
222 T
*allocate (Ts
... args
);
224 template<typename T
, typename
... Ts
>
225 T
*allocate_temp (Ts
... args
);
227 access_array
temp_access_array (access_array accesses
);
229 clobber_group
*need_clobber_group (clobber_info
*);
230 def_node
*need_def_node (def_info
*);
231 def_splay_tree
need_def_splay_tree (def_info
*);
233 use_info
*make_use_available (use_info
*, bb_info
*, bool);
234 def_array
insert_temp_clobber (obstack_watermark
&, insn_info
*,
235 unsigned int, def_array
);
237 void insert_def_before (def_info
*, def_info
*);
238 void insert_def_after (def_info
*, def_info
*);
239 void remove_def_from_list (def_info
*);
241 void add_clobber (clobber_info
*, clobber_group
*);
242 void remove_clobber (clobber_info
*, clobber_group
*);
243 void prepend_clobber_to_group (clobber_info
*, clobber_group
*);
244 void append_clobber_to_group (clobber_info
*, clobber_group
*);
245 void merge_clobber_groups (clobber_info
*, clobber_info
*,
247 clobber_info
*split_clobber_group (clobber_group
*, insn_info
*);
249 void append_def (def_info
*);
250 void add_def (def_info
*);
251 void remove_def (def_info
*);
253 void need_use_splay_tree (set_info
*);
255 static void insert_use_before (use_info
*, use_info
*);
256 static void insert_use_after (use_info
*, use_info
*);
258 void add_use (use_info
*);
259 void remove_use (use_info
*);
261 insn_info::order_node
*need_order_node (insn_info
*);
263 void add_insn_after (insn_info
*, insn_info
*);
264 void append_insn (insn_info
*);
265 void remove_insn (insn_info
*);
267 insn_info
*append_artificial_insn (bb_info
*, rtx_insn
* = nullptr);
269 void start_insn_accesses ();
270 void finish_insn_accesses (insn_info
*);
272 use_info
*create_reg_use (build_info
&, insn_info
*, resource_info
);
273 void record_use (build_info
&, insn_info
*, rtx_obj_reference
);
274 void record_call_clobbers (build_info
&, insn_info
*, rtx_call_insn
*);
275 void record_def (build_info
&, insn_info
*, rtx_obj_reference
);
276 void add_insn_to_block (build_info
&, rtx_insn
*);
278 void add_reg_unused_notes (insn_info
*);
280 void add_live_out_use (bb_info
*, set_info
*);
281 set_info
*live_out_value (bb_info
*, set_info
*);
283 void append_phi (ebb_info
*, phi_info
*);
284 void remove_phi (phi_info
*);
285 void delete_phi (phi_info
*);
286 void replace_phi (phi_info
*, set_info
*);
287 phi_info
*create_phi (ebb_info
*, resource_info
, access_info
**,
289 phi_info
*create_degenerate_phi (ebb_info
*, set_info
*);
291 bb_info
*create_bb_info (basic_block
);
292 void append_bb (bb_info
*);
294 void process_uses_of_deleted_def (set_info
*);
295 insn_info
*add_placeholder_after (insn_info
*);
296 void possibly_queue_changes (insn_change
&);
297 void finalize_new_accesses (insn_change
&, insn_info
*);
298 void apply_changes_to_insn (insn_change
&);
300 void init_function_data ();
301 void calculate_potential_phi_regs (build_info
&);
302 void place_phis (build_info
&);
303 void create_ebbs (build_info
&);
304 void add_entry_block_defs (build_info
&);
305 void calculate_ebb_live_in_for_debug (build_info
&);
306 void add_phi_nodes (build_info
&);
307 void add_artificial_accesses (build_info
&, df_ref_flags
);
308 void add_block_contents (build_info
&);
309 void record_block_live_out (build_info
&);
310 void start_block (build_info
&, bb_info
*);
311 void end_block (build_info
&, bb_info
*);
312 void populate_phi_inputs (build_info
&);
313 void process_all_blocks ();
315 void simplify_phi_setup (phi_info
*, set_info
**, bitmap
);
316 void simplify_phi_propagate (phi_info
*, set_info
**, bitmap
, bitmap
);
317 void simplify_phis ();
319 // The function that this object describes.
322 // The lowest (negative) in-use artificial insn uid minus one.
323 int m_next_artificial_uid
;
325 // The highest in-use phi uid plus one.
326 unsigned int m_next_phi_uid
;
328 // The highest in-use register number plus one.
329 unsigned int m_num_regs
;
331 // M_DEFS[R] is the first definition of register R - 1 in a reverse
332 // postorder traversal of the function, or null if the function has
333 // no definition of R. Applying last () gives the last definition of R.
335 // M_DEFS[0] is for memory; MEM_REGNO + 1 == 0.
336 auto_vec
<def_info
*> m_defs
;
338 // M_BBS[BI] gives the SSA information about the block with index BI.
339 auto_vec
<bb_info
*> m_bbs
;
341 // An obstack used to allocate the main RTL SSA information.
344 // An obstack used for temporary work, such as while building up a list
345 // of possible instruction changes.
346 obstack m_temp_obstack
;
348 // The start of each obstack, so that all memory in them can be freed.
349 char *m_obstack_start
;
350 char *m_temp_obstack_start
;
352 // The entry and exit blocks.
356 // The first and last instructions in a reverse postorder traversal
358 insn_info
*m_first_insn
;
359 insn_info
*m_last_insn
;
361 // The last nondebug instruction in the list of instructions.
362 // This is only different from m_last_insn when building the initial
363 // SSA information; after that, the last instruction is always a
364 // BB end instruction.
365 insn_info
*m_last_nondebug_insn
;
367 // Temporary working state when building up lists of definitions and uses.
368 // Keeping them around should reduce the number of unnecessary reallocations.
369 auto_vec
<access_info
*> m_temp_defs
;
370 auto_vec
<access_info
*> m_temp_uses
;
372 // A list of phis that are no longer in use. Their uids are still unique
373 // and so can be recycled.
374 phi_info
*m_free_phis
;
376 // A list of instructions that have been changed in ways that need
377 // further processing later, such as removing dead instructions or
379 auto_vec
<insn_info
*> m_queued_insn_updates
;
381 // The INSN_UIDs of all instructions in M_QUEUED_INSN_UPDATES.
382 auto_bitmap m_queued_insn_update_uids
;
384 // A basic_block is in this bitmap if we need to call purge_dead_edges
385 // on it. As with M_QUEUED_INSN_UPDATES, these updates are queued until
386 // a convenient point.
387 auto_bitmap m_need_to_purge_dead_edges
;
389 // The set of hard registers that are fully or partially clobbered
390 // by at least one insn_call_clobbers_note.
391 HARD_REG_SET m_clobbered_by_calls
;
394 void pp_function (pretty_printer
*, const function_info
*);
397 void dump (FILE *, const rtl_ssa::function_info
*);
399 void DEBUG_FUNCTION
debug (const rtl_ssa::function_info
*);