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1 : /* Manipulation of formal and actual parameters of functions and function
2 : calls.
3 : Copyright (C) 2017-2026 Free Software Foundation, Inc.
4 :
5 : This file is part of GCC.
6 :
7 : GCC is free software; you can redistribute it and/or modify it under
8 : the terms of the GNU General Public License as published by the Free
9 : Software Foundation; either version 3, or (at your option) any later
10 : version.
11 :
12 : GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 : WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 : FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 : for more details.
16 :
17 : You should have received a copy of the GNU General Public License
18 : along with GCC; see the file COPYING3. If not see
19 : <http://www.gnu.org/licenses/>.
20 :
21 :
22 :
23 : This file defines classes and other data structures that are used to manipulate
24 : the prototype of a function, especially to create, remove or split its formal
25 : parameters, but also to remove its return value, and also its call statements
26 : correspondingly.
27 :
28 : The most basic one is a vector of structures ipa_adjusted_param. It is simply
29 : a description how the new parameters should look like after the transformation
30 : in what way they relate to the previous ones (if in any). Such relation to an
31 : old parameter can be an outright copy or an IPA-SRA replacement. If an old
32 : parameter is not listed or otherwise mentioned, it is removed as unused or at
33 : least unnecessary. Note that this most basic structure does not work for
34 : modifying calls of functions with variable number of arguments.
35 :
36 : Class ipa_param_adjustments is only a little more than a thin encapsulation of
37 : a vector of ipa_param_adjustments. Along with this vector it contains an index
38 : of the first potential vararg argument and a boolean flag whether the return
39 : value should be removed or not. Moreover, the class contains method
40 : modify_call which can transform a call statement so that it correctly calls a
41 : modified function. These two data structures were designed to have a small
42 : memory footprint because they are allocated for each clone of a call graph node
43 : that has its prototype changed and live until the end of IPA clone
44 : materialization and call redirection phase.
45 :
46 : On the other hand, class ipa_param_body_adjustments can afford to allocate more
47 : data because its life span is much smaller, it is allocated and destroyed in
48 : the course of materialization of each single clone that needs it or only when a
49 : particular pass needs to change a function it is operating on. This class has
50 : various methods required to change function declaration and the body of the
51 : function according to instructions given either by class ipa_param_adjustments
52 : or only a vector of ipa_adjusted_params.
53 :
54 : When these classes are used in the context of call graph clone materialization
55 : and subsequent call statement redirection - which is the point at which we
56 : modify arguments in call statements - they need to cooperate with each other in
57 : order to handle what we refer to as pass-through (IPA-SRA) splits. These are
58 : situations when a formal parameter of one function is split into several
59 : smaller ones and some of them are then passed on in a call to another function
60 : because the formal parameter of this callee has also been split.
61 :
62 : Consider a simple example:
63 :
64 : struct S {int a, b, c;};
65 : struct Z {int x; S s;};
66 :
67 : foo (S s)
68 : {
69 : use (s.b);
70 : }
71 :
72 : bar (Z z)
73 : {
74 : use (z.s.a);
75 : foo (z.s);
76 : }
77 :
78 : baz ()
79 : {
80 : bar (*global);
81 : }
82 :
83 : Both bar and foo would have their parameter split. Foo would receive one
84 : replacement representing s.b. Function bar would see its parameter split into
85 : one replacement representing z.s.a and another representing z.s.b which would
86 : be passed on to foo. It would be a so called pass-through split IPA-SRA
87 : replacement, one which is passed in a call as an actual argument to another
88 : IPA-SRA replacement in another function.
89 :
90 : Note that the call chain the example can be arbitrarily long and recursive and
91 : that any function in it can be cloned by another IPA pass and any number of
92 : adjacent functions in the call chain can be inlined into each other. Call
93 : redirection takes place only after bodies of the function have been modified by
94 : all of the above.
95 :
96 : Call redirection has to be able to find the right decl or SSA_NAME that
97 : corresponds to the transitive split in the caller. The SSA names are assigned
98 : right after clone materialization/ modification and cannot be "added" to call
99 : arguments at any later point. Moreover, if the caller has been inlined the
100 : SSA_NAMEs in question no longer belong to PARM_DECLs but to VAR_DECLs,
101 : indistinguishable from any others.
102 :
103 : Therefore, when clone materialization finds a call statement which it knows is
104 : a part of a transitive split, it will simply add as arguments all new "split"
105 : replacements (that have grater or equal offset than the original call
106 : argument):
107 :
108 : foo (repl_for_a, repl_for_b, <rest of original arguments>);
109 :
110 : It will also store into ipa_edge_modification_info (which is internal to
111 : ipa-param-modification.c) information about which replacement is which and
112 : where original arguments are. Call redirection will then invoke
113 : ipa_param_adjustments::modify_call which will access this information and
114 : eliminate all replacements which the callee does not expect (repl_for_a in our
115 : example above). In between these two steps, however, a call statement might
116 : have extraneous arguments. */
117 :
118 : #ifndef IPA_PARAM_MANIPULATION_H
119 : #define IPA_PARAM_MANIPULATION_H
120 :
121 : /* Indices into ipa_param_prefixes to identify a human-readable prefix for newly
122 : synthesized parameters. Keep in sync with the array. */
123 : enum ipa_param_name_prefix_indices
124 : {
125 : IPA_PARAM_PREFIX_SYNTH,
126 : IPA_PARAM_PREFIX_ISRA,
127 : IPA_PARAM_PREFIX_SIMD,
128 : IPA_PARAM_PREFIX_MASK,
129 : IPA_PARAM_PREFIX_COUNT
130 : };
131 :
132 : /* We do not support manipulating functions with more than
133 : 1<<IPA_PARAM_MAX_INDEX_BITS parameters. */
134 : #define IPA_PARAM_MAX_INDEX_BITS 16
135 :
136 : /* Operation to be performed for the parameter in ipa_parm_adjustment
137 : below. */
138 :
139 : enum ipa_parm_op
140 : {
141 : /* Do not use or you will trigger an assert. */
142 : IPA_PARAM_OP_UNDEFINED,
143 :
144 : /* This new parameter is an unmodified parameter at index base_index. */
145 : IPA_PARAM_OP_COPY,
146 :
147 : /* This describes a brand new parameter. If it somehow relates to any
148 : original parameters, the user needs to manage the transition itself. */
149 : IPA_PARAM_OP_NEW,
150 :
151 : /* Split parameter as indicated by fields base_index, offset and type. */
152 : IPA_PARAM_OP_SPLIT
153 : };
154 :
155 : /* Structure that describes one parameter of a function after transformation.
156 : Omitted parameters will be removed. */
157 :
158 : struct GTY(()) ipa_adjusted_param
159 : {
160 : /* Type of the new parameter. Required for all operations except
161 : IPA_PARM_OP_COPY when the original type will be preserved. */
162 : tree type;
163 :
164 : /* Alias reference type to be used in MEM_REFs when adjusting caller
165 : arguments. Required for IPA_PARM_OP_SPLIT operation. */
166 : tree alias_ptr_type;
167 :
168 : /* Offset into the original parameter (for the cases when the new parameter
169 : is a component of an original one). Required for IPA_PARM_OP_SPLIT
170 : operation. */
171 : unsigned unit_offset;
172 :
173 : /* Zero based index of the original parameter this one is based on. Required
174 : for IPA_PARAM_OP_COPY and IPA_PARAM_OP_SPLIT, users of IPA_PARAM_OP_NEW
175 : only need to specify it if they use replacement lookup provided by
176 : ipa_param_body_adjustments. */
177 : unsigned base_index : IPA_PARAM_MAX_INDEX_BITS;
178 :
179 : /* Zero based index of the parameter this one is based on in the previous
180 : clone. If there is no previous clone, it must be equal to base_index. */
181 : unsigned prev_clone_index : IPA_PARAM_MAX_INDEX_BITS;
182 :
183 : /* Specify the operation, if any, to be performed on the parameter. */
184 : enum ipa_parm_op op : 2;
185 :
186 : /* If set, this structure describes a parameter copied over from a previous
187 : IPA clone, any transformations are thus not to be re-done. */
188 : unsigned prev_clone_adjustment : 1;
189 :
190 : /* Index into ipa_param_prefixes specifying a prefix to be used with
191 : DECL_NAMEs of newly synthesized parameters. */
192 : unsigned param_prefix_index : 2;
193 :
194 : /* Storage order of the original parameter (for the cases when the new
195 : parameter is a component of an original one). */
196 : unsigned reverse : 1;
197 :
198 : /* A bit free for the user. */
199 : unsigned user_flag : 1;
200 : };
201 :
202 : void ipa_dump_adjusted_parameters (FILE *f,
203 : vec<ipa_adjusted_param, va_gc> *adj_params);
204 :
205 : /* Class used to record planned modifications to parameters of a function and
206 : also to perform necessary modifications at the caller side at the gimple
207 : level. Used to describe all cgraph node clones that have their parameters
208 : changed, therefore the class should only have a small memory footprint. */
209 :
210 : class GTY(()) ipa_param_adjustments
211 : {
212 : public:
213 : /* Constructor from NEW_PARAMS showing how new parameters should look like
214 : plus copying any pre-existing actual arguments starting from argument
215 : with index ALWAYS_COPY_START (if non-negative, negative means do not copy
216 : anything beyond what is described in NEW_PARAMS), and SKIP_RETURN, which
217 : indicates that the function should return void after transformation. */
218 :
219 171212 : ipa_param_adjustments (vec<ipa_adjusted_param, va_gc> *new_params,
220 : int always_copy_start, bool skip_return)
221 171212 : : m_adj_params (new_params), m_always_copy_start (always_copy_start),
222 171212 : m_skip_return (skip_return)
223 : {}
224 :
225 : /* Modify a call statement arguments (and possibly remove the return value)
226 : as described in the data fields of this class. */
227 : gcall *modify_call (cgraph_edge *cs, bool update_references,
228 : hash_set <tree> *killed_ssas);
229 : /* Return if the first parameter is left intact. */
230 : bool first_param_intact_p ();
231 : /* Build a function type corresponding to the modified call. */
232 : tree build_new_function_type (tree old_type, bool type_is_original_p,
233 : bool *args_modified = NULL);
234 : /* Build a declaration corresponding to the target of the modified call. */
235 : tree adjust_decl (tree orig_decl);
236 : /* Fill a vector marking which parameters are intact by the described
237 : modifications. */
238 : void get_surviving_params (vec<bool> *surviving_params);
239 : /* Fill a vector with new indices of surviving original parameters. */
240 : void get_updated_indices (vec<int> *new_indices);
241 : /* Return the original index for the given new parameter index. Return a
242 : negative number if not available. */
243 : int get_original_index (int newidx);
244 :
245 : void dump (FILE *f);
246 : void debug ();
247 :
248 : /* How the known part of arguments should look like. */
249 : vec<ipa_adjusted_param, va_gc> *m_adj_params;
250 :
251 : /* If non-negative, copy any arguments starting at this offset without any
252 : modifications so that functions with variable number of arguments can be
253 : modified. This number should be equal to the number of original forma
254 : parameters. */
255 : int m_always_copy_start;
256 : /* If true, make the function not return any value. */
257 : bool m_skip_return;
258 :
259 : static bool type_attribute_allowed_p (tree);
260 : private:
261 : ipa_param_adjustments () {}
262 :
263 : void init (vec<tree> *cur_params);
264 : int get_max_base_index ();
265 : bool method2func_p (tree orig_type);
266 : };
267 :
268 : /* Structure used to map expressions accessing split or replaced parameters to
269 : new PARM_DECLs. */
270 :
271 : struct ipa_param_body_replacement
272 : {
273 : /* The old decl of the original parameter. */
274 : tree base;
275 : /* The new decl it should be replaced with. */
276 : tree repl;
277 : /* Users of ipa_param_body_adjustments that modify standalone functions
278 : outside of IPA clone materialization can use the following field for their
279 : internal purposes. */
280 : tree dummy;
281 : /* The offset within BASE that REPL represents. */
282 : unsigned unit_offset;
283 : };
284 :
285 : struct ipa_replace_map;
286 :
287 : /* Class used when actually performing adjustments to formal parameters of a
288 : function to map accesses that need to be replaced to replacements. The
289 : class attempts to work in two very different sets of circumstances: as a
290 : part of tree-inine.c's tree_function_versioning machinery to clone functions
291 : (when M_ID is not NULL) and in s standalone fashion, modifying an existing
292 : function in place (when M_ID is NULL). While a lot of stuff handled in a
293 : unified way in both modes, there are many aspects of the processs that
294 : requires distinct paths. */
295 :
296 : class ipa_param_body_adjustments
297 : {
298 : public:
299 : /* Constructor to use from within tree-inline. */
300 : ipa_param_body_adjustments (ipa_param_adjustments *adjustments,
301 : tree fndecl, tree old_fndecl,
302 : struct copy_body_data *id, tree *vars,
303 : vec<ipa_replace_map *, va_gc> *tree_map);
304 : /* Constructor to use for modifying a function outside of tree-inline from an
305 : instance of ipa_param_adjustments. */
306 : ipa_param_body_adjustments (ipa_param_adjustments *adjustments,
307 : tree fndecl);
308 : /* Constructor to use for modifying a function outside of tree-inline from a
309 : simple vector of desired parameter modification. */
310 : ipa_param_body_adjustments (vec<ipa_adjusted_param, va_gc> *adj_params,
311 : tree fndecl);
312 :
313 : /* The do-it-all function for modifying a function outside of
314 : tree-inline. */
315 : bool perform_cfun_body_modifications ();
316 :
317 : /* Change the PARM_DECLs. */
318 : void modify_formal_parameters ();
319 : /* Register a REPLACEMENT for accesses to BASE at UNIT_OFFSET. */
320 : void register_replacement (tree base, unsigned unit_offset, tree replacement);
321 : /* Register a replacement decl for the transformation done in APM. */
322 : void register_replacement (ipa_adjusted_param *apm, tree replacement);
323 : /* Sort m_replacements and set m_sorted_replacements_p to true. Users that
324 : call register_replacement themselves must call the method before any
325 : lookup and thus also any statement or expression modification. */
326 : void sort_replacements ();
327 : /* Lookup a replacement for a given offset within a given parameter. */
328 : tree lookup_replacement (tree base, unsigned unit_offset);
329 : /* Lookup a replacement for an expression, if there is one. */
330 : ipa_param_body_replacement *get_expr_replacement (tree expr,
331 : bool ignore_default_def);
332 : /* Lookup the new base for surviving names previously belonging to a
333 : parameter. */
334 : tree get_replacement_ssa_base (tree old_decl);
335 : /* Modify a statement. */
336 : bool modify_gimple_stmt (gimple **stmt, gimple_seq *extra_stmts,
337 : gimple *orig_stmt);
338 : /* Return the new chain of parameters. */
339 : tree get_new_param_chain ();
340 : /* Replace all occurances of SSAs in m_dead_ssa_debug_equiv in t with what
341 : they are mapped to. */
342 : void remap_with_debug_expressions (tree *t);
343 :
344 : /* If there are any initialization statements that need to be emitted into
345 : the basic block BB right at ther start of the new function, do so. */
346 : void append_init_stmts (basic_block bb);
347 :
348 : /* Pointers to data structures defining how the function should be
349 : modified. */
350 : vec<ipa_adjusted_param, va_gc> *m_adj_params;
351 : ipa_param_adjustments *m_adjustments;
352 :
353 : /* Vector of old parameter declarations that must have their debug bind
354 : statements re-mapped and debug decls created. */
355 :
356 : auto_vec<tree, 16> m_reset_debug_decls;
357 :
358 : /* Sets of statements and SSA_NAMEs that only manipulate data from parameters
359 : removed because they are not necessary. */
360 : hash_set<gimple *> m_dead_stmts;
361 : hash_set<tree> m_dead_ssas;
362 :
363 : /* Mapping from DCEd SSAs to what their potential debug_binds should be. */
364 : hash_map<tree, tree> m_dead_ssa_debug_equiv;
365 : /* Mapping from DCEd statements to debug expressions that will be placed on
366 : the RHS of debug statement that will replace this one. */
367 : hash_map<gimple *, tree> m_dead_stmt_debug_equiv;
368 :
369 : private:
370 : void common_initialization (tree old_fndecl, tree *vars,
371 : vec<ipa_replace_map *, va_gc> *tree_map);
372 : tree carry_over_param (tree t);
373 : unsigned get_base_index (ipa_adjusted_param *apm);
374 : ipa_param_body_replacement *lookup_replacement_1 (tree base,
375 : unsigned unit_offset);
376 : ipa_param_body_replacement *lookup_first_base_replacement (tree base);
377 : tree replace_removed_params_ssa_names (tree old_name, gimple *stmt);
378 : bool modify_expression (tree *expr_p, bool convert, gimple_seq * = nullptr);
379 : bool modify_assignment (gimple *stmt, gimple_seq *extra_stmts);
380 : bool modify_call_stmt (gcall **stmt_p, gimple *orig_stmt);
381 : bool modify_cfun_body ();
382 : void reset_debug_stmts ();
383 : tree get_ddef_if_exists_and_is_used (tree decl);
384 : void mark_dead_statements (tree dead_param, vec<tree> *debugstack);
385 : void mark_clobbers_dead (tree dead_param);
386 : bool prepare_debug_expressions (tree dead_ssa);
387 :
388 : /* Declaration of the function that is being transformed. */
389 :
390 : tree m_fndecl;
391 :
392 : /* If non-NULL, the tree-inline master data structure guiding materialization
393 : of the current clone. */
394 : struct copy_body_data *m_id;
395 :
396 : /* Vector of old parameter declarations (before changing them). */
397 :
398 : auto_vec<tree, 16> m_oparms;
399 :
400 : /* Vector of parameter declarations the function will have after
401 : transformation. */
402 :
403 : auto_vec<tree, 16> m_new_decls;
404 :
405 : /* If the function type has non-NULL TYPE_ARG_TYPES, this is the vector of
406 : these types after transformation, otherwise an empty one. */
407 :
408 : auto_vec<tree, 16> m_new_types;
409 :
410 : /* Vector of structures telling how to replace old parameters in the
411 : function body. TODO: Even though there usually be only few, but should we
412 : use a hash? */
413 :
414 : auto_vec<ipa_param_body_replacement, 16> m_replacements;
415 :
416 : /* List of initialization assignments to be put at the beginning of the
417 : cloned function to deal with split aggregates which however have known
418 : constant value and so their PARM_DECL disappears. */
419 :
420 : auto_vec<gimple *, 8> m_split_agg_csts_inits;
421 :
422 : /* Vector for remapping SSA_BASES from old parameter declarations that are
423 : being removed as a part of the transformation. Before a new VAR_DECL is
424 : created, it holds the old PARM_DECL, once the variable is built it is
425 : stored here. */
426 :
427 : auto_vec<tree> m_removed_decls;
428 :
429 : /* Hash to quickly lookup the item in m_removed_decls given the old decl. */
430 :
431 : hash_map<tree, unsigned> m_removed_map;
432 :
433 : /* True iff the transformed function is a class method that is about to loose
434 : its this pointer and must be converted to a normal function. */
435 :
436 : bool m_method2func;
437 :
438 : /* True if m_replacements have ben sorted since the last insertion. */
439 :
440 : bool m_sorted_replacements_p;
441 : };
442 :
443 : void push_function_arg_decls (vec<tree> *args, tree fndecl);
444 : void push_function_arg_types (vec<tree> *types, tree fntype);
445 : void ipa_verify_edge_has_no_modifications (cgraph_edge *cs);
446 : void ipa_edge_modifications_finalize ();
447 : void ipa_release_ssas_in_hash (hash_set <tree> *killed_ssas);
448 :
449 : #endif /* IPA_PARAM_MANIPULATION_H */
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