gcc/ipa-fnsummary.h

   1 /* IPA function body analysis.
   2    Copyright (C) 2003-2023 Free Software Foundation, Inc.
   3    Contributed by Jan Hubicka
   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 #ifndef GCC_IPA_SUMMARY_H
  22 #define GCC_IPA_SUMMARY_H
  23
  24 #include "sreal.h"
  25 #include "ipa-predicate.h"
  26
  27
  28 /* Hints are reasons why IPA heuristics should prefer specializing given
  29    function.  They are represented as bitmap of the following values.  */
  30 enum ipa_hints_vals {
  31   /* When specialization turns indirect call into a direct call,
  32      it is good idea to do so.  */
  33   INLINE_HINT_indirect_call = 1,
  34   /* Inlining may make loop iterations or loop stride known.  It is good idea
  35      to do so because it enables loop optimizations.  */
  36   INLINE_HINT_loop_iterations = 2,
  37   INLINE_HINT_loop_stride = 4,
  38   /* Inlining within same strongly connected component of callgraph is often
  39      a loss due to increased stack frame usage and prologue setup costs.  */
  40   INLINE_HINT_same_scc = 8,
  41   /* Inlining functions in strongly connected component is not such a great
  42      win.  */
  43   INLINE_HINT_in_scc = 16,
  44   /* If function is declared inline by user, it may be good idea to inline
  45      it.  Set by simple_edge_hints in ipa-inline-analysis.cc.  */
  46   INLINE_HINT_declared_inline = 32,
  47   /* Programs are usually still organized for non-LTO compilation and thus
  48      if functions are in different modules, inlining may not be so important.
  49      Set by simple_edge_hints in ipa-inline-analysis.cc.   */
  50   INLINE_HINT_cross_module = 64,
  51   /* We know that the callee is hot by profile.  */
  52   INLINE_HINT_known_hot = 128,
  53   /* There is builtin_constant_p dependent on parameter which is usually
  54      a strong hint to inline.  */
  55   INLINE_HINT_builtin_constant_p = 256
  56 };
  57
  58 typedef int ipa_hints;
  59
  60 /* Simple description of whether a memory load or a condition refers to a load
  61    from an aggregate and if so, how and where from in the aggregate.
  62    Individual fields have the same meaning like fields with the same name in
  63    struct condition.  */
  64
  65 struct agg_position_info
  66 {
  67   HOST_WIDE_INT offset;
  68   bool agg_contents;
  69   bool by_ref;
  70 };
  71
  72 /* Representation of function body size and time depending on the call
  73    context.  We keep simple array of record, every containing of predicate
  74    and time/size to account.  */
  75 class size_time_entry
  76 {
  77 public:
  78   /* Predicate for code to be executed.  */
  79   ipa_predicate exec_predicate;
  80   /* Predicate for value to be constant and optimized out in a specialized copy.
  81      When deciding on specialization this makes it possible to see how much
  82      the executed code paths will simplify.  */
  83   ipa_predicate nonconst_predicate;
  84   int size;
  85   sreal time;
  86 };
  87
  88 /* Summary about function and stack frame sizes.  We keep this info
  89    for inline clones and also for WPA streaming. For this reason this is not
  90    part of ipa_fn_summary which exists only for offline functions.  */
  91 class ipa_size_summary
  92 {
  93 public:
  94   /* Estimated stack frame consumption by the function.  */
  95   HOST_WIDE_INT estimated_self_stack_size;
  96   /* Size of the function body.  */
  97   int self_size;
  98   /* Estimated size of the function after inlining.  */
  99   int size;
 100
 101   ipa_size_summary ()
 102   : estimated_self_stack_size (0), self_size (0), size (0)
 103   {
 104   }
 105 };
 106
 107 /* Structure to capture how frequently some interesting events occur given a
 108    particular predicate.  The structure is used to estimate how often we
 109    encounter loops with known iteration count or stride in various
 110    contexts.  */
 111
 112 struct GTY(()) ipa_freqcounting_predicate
 113 {
 114   /* The described event happens with this frequency... */
 115   sreal freq;
 116   /* ...when this predicate evaluates to false. */
 117   ipa_predicate * GTY((skip)) predicate;
 118 };
 119
 120 /* Function inlining information.  */
 121 class GTY(()) ipa_fn_summary
 122 {
 123 public:
 124   /* Keep all field empty so summary dumping works during its computation.
 125      This is useful for debugging.  */
 126   ipa_fn_summary ()
 127     : min_size (0),
 128       inlinable (false), single_caller (false),
 129       fp_expressions (false), target_info (0),
 130       estimated_stack_size (false),
 131       time (0), conds (NULL),
 132       size_time_table (), call_size_time_table (vNULL),
 133       loop_iterations (NULL), loop_strides (NULL),
 134       builtin_constant_p_parms (vNULL),
 135       growth (0), scc_no (0)
 136   {
 137   }
 138
 139   /* Copy constructor.  */
 140   ipa_fn_summary (const ipa_fn_summary &s)
 141     : min_size (s.min_size),
 142     inlinable (s.inlinable), single_caller (s.single_caller),
 143     fp_expressions (s.fp_expressions),
 144     target_info (s.target_info),
 145     estimated_stack_size (s.estimated_stack_size),
 146     time (s.time), conds (s.conds), size_time_table (),
 147     call_size_time_table (vNULL),
 148     loop_iterations (s.loop_iterations), loop_strides (s.loop_strides),
 149     builtin_constant_p_parms (s.builtin_constant_p_parms),
 150     growth (s.growth), scc_no (s.scc_no)
 151   {}
 152
 153   /* Default constructor.  */
 154   ~ipa_fn_summary ();
 155
 156   /* Information about the function body itself.  */
 157
 158   /* Minimal size increase after inlining.  */
 159   int min_size;
 160
 161   /* False when there something makes inlining impossible (such as va_arg).  */
 162   unsigned inlinable : 1;
 163   /* True wen there is only one caller of the function before small function
 164      inlining.  */
 165   unsigned int single_caller : 1;
 166   /* True if function contains any floating point expressions.  */
 167   unsigned int fp_expressions : 1;
 168   /* Like fp_expressions field above, but it's to hold some target specific
 169      information, such as some target specific isa flags.  Note that for
 170      offloading target compilers, this field isn't streamed.  */
 171   unsigned int target_info;
 172
 173   /* Information about function that will result after applying all the
 174      inline decisions present in the callgraph.  Generally kept up to
 175      date only for functions that are not inline clones. */
 176
 177   /* Estimated stack frame consumption by the function.  */
 178   HOST_WIDE_INT estimated_stack_size;
 179   /* Estimated runtime of function after inlining.  */
 180   sreal GTY((skip)) time;
 181
 182   /* Conditional size/time information.  The summaries are being
 183      merged during inlining.  */
 184   conditions conds;
 185   /* Normal code is accounted in size_time_table, while calls are
 186      accounted in call_size_time_table.  This is because calls
 187      are often adjusted by IPA optimizations and thus this summary
 188      is generated from call summary information when needed.  */
 189   auto_vec<size_time_entry> GTY((skip)) size_time_table;
 190   /* Unlike size_time_table that is initialized for all summaries
 191      call_size_time_table is allocated only for functions with
 192      many calls.  Use effecient vl_ptr storage.  */
 193   vec<size_time_entry, va_heap, vl_ptr> GTY((skip)) call_size_time_table;
 194
 195   /* Predicates on when some loops in the function can have known bounds.  */
 196   vec<ipa_freqcounting_predicate, va_gc> *loop_iterations;
 197   /* Predicates on when some loops in the function can have known strides.  */
 198   vec<ipa_freqcounting_predicate, va_gc> *loop_strides;
 199   /* Parameters tested by builtin_constant_p.  */
 200   vec<int, va_heap, vl_ptr> GTY((skip)) builtin_constant_p_parms;
 201   /* Estimated growth for inlining all copies of the function before start
 202      of small functions inlining.
 203      This value will get out of date as the callers are duplicated, but
 204      using up-to-date value in the badness metric mean a lot of extra
 205      expenses.  */
 206   int growth;
 207   /* Number of SCC on the beginning of inlining process.  */
 208   int scc_no;
 209
 210   /* Record time and size under given predicates.  */
 211   void account_size_time (int, sreal, const ipa_predicate &,
 212                           const ipa_predicate &,
 213                           bool call = false);
 214
 215   /* We keep values scaled up, so fractional sizes can be accounted.  */
 216   static const int size_scale = 2;
 217   /* Maximal size of size_time_table before we start to be conservative.  */
 218   static const int max_size_time_table_size = 256;
 219 };
 220
 221 class GTY((user)) ipa_fn_summary_t:
 222   public fast_function_summary <ipa_fn_summary *, va_gc>
 223 {
 224 public:
 225   ipa_fn_summary_t (symbol_table *symtab):
 226     fast_function_summary <ipa_fn_summary *, va_gc> (symtab) {}
 227
 228   static ipa_fn_summary_t *create_ggc (symbol_table *symtab)
 229   {
 230     class ipa_fn_summary_t *summary
 231       = new (ggc_alloc_no_dtor<ipa_fn_summary_t> ()) ipa_fn_summary_t (symtab);
 232     summary->disable_insertion_hook ();
 233     return summary;
 234   }
 235
 236   /* Remove ipa_fn_summary for all callees of NODE.  */
 237   void remove_callees (cgraph_node *node);
 238
 239   void insert (cgraph_node *, ipa_fn_summary *) final override;
 240   void remove (cgraph_node *node, ipa_fn_summary *) final override
 241   {
 242     remove_callees (node);
 243   }
 244
 245   void duplicate (cgraph_node *src, cgraph_node *dst,
 246                   ipa_fn_summary *src_data, ipa_fn_summary *dst_data)
 247     final override;
 248 };
 249
 250 extern GTY(()) fast_function_summary <ipa_fn_summary *, va_gc>
 251   *ipa_fn_summaries;
 252
 253 class ipa_size_summary_t:
 254   public fast_function_summary <ipa_size_summary *, va_heap>
 255 {
 256 public:
 257   ipa_size_summary_t (symbol_table *symtab):
 258     fast_function_summary <ipa_size_summary *, va_heap> (symtab)
 259   {
 260     disable_insertion_hook ();
 261   }
 262
 263   void duplicate (cgraph_node *, cgraph_node *,
 264                   ipa_size_summary *src_data,
 265                   ipa_size_summary *dst_data) final override
 266   {
 267     *dst_data = *src_data;
 268   }
 269 };
 270 extern fast_function_summary <ipa_size_summary *, va_heap>
 271   *ipa_size_summaries;
 272
 273 /* Information kept about callgraph edges.  */
 274 class ipa_call_summary
 275 {
 276 public:
 277   /* Keep all field empty so summary dumping works during its computation.
 278      This is useful for debugging.  */
 279   ipa_call_summary ()
 280     : predicate (NULL), param (vNULL), call_stmt_size (0), call_stmt_time (0),
 281       loop_depth (0), is_return_callee_uncaptured (false)
 282     {
 283     }
 284
 285   /* Copy constructor.  */
 286   ipa_call_summary (const ipa_call_summary &s):
 287     predicate (s.predicate), param (s.param), call_stmt_size (s.call_stmt_size),
 288     call_stmt_time (s.call_stmt_time), loop_depth (s.loop_depth),
 289     is_return_callee_uncaptured (s.is_return_callee_uncaptured)
 290   {
 291   }
 292
 293   /* Default destructor.  */
 294   ~ipa_call_summary ();
 295
 296   ipa_predicate *predicate;
 297   /* Vector indexed by parameters.  */
 298   vec<inline_param_summary> param;
 299   /* Estimated size and time of the call statement.  */
 300   int call_stmt_size;
 301   int call_stmt_time;
 302   /* Depth of loop nest, 0 means no nesting.  */
 303   unsigned int loop_depth;
 304   /* Indicates whether the caller returns the value of it's callee.  */
 305   bool is_return_callee_uncaptured;
 306 };
 307
 308 class ipa_call_summary_t: public fast_call_summary <ipa_call_summary *, va_heap>
 309 {
 310 public:
 311   ipa_call_summary_t (symbol_table *symtab):
 312     fast_call_summary <ipa_call_summary *, va_heap> (symtab) {}
 313
 314   /* Hook that is called by summary when an edge is duplicated.  */
 315   void duplicate (cgraph_edge *src, cgraph_edge *dst,
 316                   ipa_call_summary *src_data,
 317                   ipa_call_summary *dst_data) final override;
 318 };
 319
 320 /* Estimated execution times, code sizes and other information about the
 321    code executing a call described by ipa_call_context.  */
 322
 323 struct ipa_call_estimates
 324 {
 325   /* Estimated size needed to execute call in the given context. */
 326   int size;
 327
 328   /* Minimal size needed for the call that is + independent on the call context
 329      and can be used for fast estimates.  */
 330   int min_size;
 331
 332   /* Estimated time needed to execute call in the given context. */
 333   sreal time;
 334
 335   /* Estimated time needed to execute the function when not ignoring
 336      computations known to be constant in this context.  */
 337   sreal nonspecialized_time;
 338
 339   /* Further discovered reasons why to inline or specialize the give calls.  */
 340   ipa_hints hints;
 341
 342   /* Frequency how often a loop with known number of iterations is encountered.
 343      Calculated with hints.  */
 344   sreal loops_with_known_iterations;
 345
 346   /* Frequency how often a loop with known strides is encountered.  Calculated
 347      with hints.  */
 348   sreal loops_with_known_strides;
 349 };
 350
 351 class ipa_cached_call_context;
 352
 353 /* This object describe a context of call.  That is a summary of known
 354    information about its parameters.  Main purpose of this context is
 355    to give more realistic estimations of function runtime, size and
 356    inline hints.  */
 357 class ipa_call_context
 358 {
 359 public:
 360   ipa_call_context (cgraph_node *node,
 361                     clause_t possible_truths,
 362                     clause_t nonspec_possible_truths,
 363                     vec<inline_param_summary> inline_param_summary,
 364                     ipa_auto_call_arg_values *arg_values);
 365   ipa_call_context ()
 366   : m_node(NULL)
 367   {
 368   }
 369   void estimate_size_and_time (ipa_call_estimates *estimates,
 370                                bool est_times = true, bool est_hints = true);
 371   bool equal_to (const ipa_call_context &);
 372   bool exists_p ()
 373   {
 374     return m_node != NULL;
 375   }
 376 private:
 377   /* Called function.  */
 378   cgraph_node *m_node;
 379   /* Clause describing what predicate conditionals can be satisfied
 380      in this context if function is inlined/specialized.  */
 381   clause_t m_possible_truths;
 382   /* Clause describing what predicate conditionals can be satisfied
 383      in this context if function is kept offline.  */
 384   clause_t m_nonspec_possible_truths;
 385   /* Inline summary maintains info about change probabilities.  */
 386   vec<inline_param_summary> m_inline_param_summary;
 387
 388   /* Even after having calculated clauses, the information about argument
 389      values is used to resolve indirect calls.  */
 390   ipa_call_arg_values m_avals;
 391
 392   friend ipa_cached_call_context;
 393 };
 394
 395 /* Variant of ipa_call_context that is stored in a cache over a longer period
 396    of time.  */
 397
 398 class ipa_cached_call_context : public ipa_call_context
 399 {
 400 public:
 401   void duplicate_from (const ipa_call_context &ctx);
 402   void release ();
 403 };
 404
 405 extern fast_call_summary <ipa_call_summary *, va_heap> *ipa_call_summaries;
 406
 407 /* In ipa-fnsummary.cc  */
 408 void ipa_debug_fn_summary (struct cgraph_node *);
 409 void ipa_dump_fn_summaries (FILE *f);
 410 void ipa_dump_fn_summary (FILE *f, struct cgraph_node *node);
 411 void ipa_dump_hints (FILE *f, ipa_hints);
 412 void ipa_free_fn_summary (void);
 413 void ipa_free_size_summary (void);
 414 void inline_analyze_function (struct cgraph_node *node);
 415 void estimate_ipcp_clone_size_and_time (struct cgraph_node *node,
 416                                         ipa_auto_call_arg_values *avals,
 417                                         ipa_call_estimates *estimates);
 418 void ipa_merge_fn_summary_after_inlining (struct cgraph_edge *edge);
 419 void ipa_update_overall_fn_summary (struct cgraph_node *node, bool reset = true);
 420 void compute_fn_summary (struct cgraph_node *, bool);
 421 bool refs_local_or_readonly_memory_p (tree);
 422 bool points_to_local_or_readonly_memory_p (tree);
 423
 424
 425 void evaluate_properties_for_edge (struct cgraph_edge *e,
 426                                    bool inline_p,
 427                                    clause_t *clause_ptr,
 428                                    clause_t *nonspec_clause_ptr,
 429                                    ipa_auto_call_arg_values *avals,
 430                                    bool compute_contexts);
 431
 432 void ipa_fnsummary_cc_finalize (void);
 433 HOST_WIDE_INT ipa_get_stack_frame_offset (struct cgraph_node *node);
 434 void ipa_remove_from_growth_caches (struct cgraph_edge *edge);
 435
 436 /* Return true if EDGE is a cross module call.  */
 437
 438 static inline bool
 439 cross_module_call_p (struct cgraph_edge *edge)
 440 {
 441   /* Here we do not want to walk to alias target becuase ICF may create
 442      cross-unit aliases.  */
 443   if (edge->caller->unit_id == edge->callee->unit_id)
 444     return false;
 445   /* If the call is to a (former) comdat function or s symbol with mutiple
 446      extern inline definitions then treat is as in-module call.  */
 447   if (edge->callee->merged_extern_inline || edge->callee->merged_comdat
 448       || DECL_COMDAT (edge->callee->decl))
 449     return false;
 450   return true;
 451 }
 452
 453 #endif /* GCC_IPA_FNSUMMARY_H */