gcc/ipa-fnsummary.h

   1 /* IPA function body analysis.
   2    Copyright (C) 2003-2021 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.c.  */
  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.c.   */
  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),
 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     estimated_stack_size (s.estimated_stack_size),
 145     time (s.time), conds (s.conds), size_time_table (),
 146     call_size_time_table (vNULL),
 147     loop_iterations (s.loop_iterations), loop_strides (s.loop_strides),
 148     builtin_constant_p_parms (s.builtin_constant_p_parms),
 149     growth (s.growth), scc_no (s.scc_no)
 150   {}
 151
 152   /* Default constructor.  */
 153   ~ipa_fn_summary ();
 154
 155   /* Information about the function body itself.  */
 156
 157   /* Minimal size increase after inlining.  */
 158   int min_size;
 159
 160   /* False when there something makes inlining impossible (such as va_arg).  */
 161   unsigned inlinable : 1;
 162   /* True wen there is only one caller of the function before small function
 163      inlining.  */
 164   unsigned int single_caller : 1;
 165   /* True if function contains any floating point expressions.  */
 166   unsigned int fp_expressions : 1;
 167
 168   /* Information about function that will result after applying all the
 169      inline decisions present in the callgraph.  Generally kept up to
 170      date only for functions that are not inline clones. */
 171
 172   /* Estimated stack frame consumption by the function.  */
 173   HOST_WIDE_INT estimated_stack_size;
 174   /* Estimated runtime of function after inlining.  */
 175   sreal GTY((skip)) time;
 176
 177   /* Conditional size/time information.  The summaries are being
 178      merged during inlining.  */
 179   conditions conds;
 180   /* Normal code is accounted in size_time_table, while calls are
 181      accounted in call_size_time_table.  This is because calls
 182      are often adjusted by IPA optimizations and thus this summary
 183      is generated from call summary information when needed.  */
 184   auto_vec<size_time_entry> GTY((skip)) size_time_table;
 185   /* Unlike size_time_table that is initialized for all summaries
 186      call_size_time_table is allocated only for functions with
 187      many calls.  Use effecient vl_ptr storage.  */
 188   vec<size_time_entry, va_heap, vl_ptr> GTY((skip)) call_size_time_table;
 189
 190   /* Predicates on when some loops in the function can have known bounds.  */
 191   vec<ipa_freqcounting_predicate, va_gc> *loop_iterations;
 192   /* Predicates on when some loops in the function can have known strides.  */
 193   vec<ipa_freqcounting_predicate, va_gc> *loop_strides;
 194   /* Parameters tested by builtin_constant_p.  */
 195   vec<int, va_heap, vl_ptr> GTY((skip)) builtin_constant_p_parms;
 196   /* Estimated growth for inlining all copies of the function before start
 197      of small functions inlining.
 198      This value will get out of date as the callers are duplicated, but
 199      using up-to-date value in the badness metric mean a lot of extra
 200      expenses.  */
 201   int growth;
 202   /* Number of SCC on the beginning of inlining process.  */
 203   int scc_no;
 204
 205   /* Record time and size under given predicates.  */
 206   void account_size_time (int, sreal, const ipa_predicate &,
 207                           const ipa_predicate &,
 208                           bool call = false);
 209
 210   /* We keep values scaled up, so fractional sizes can be accounted.  */
 211   static const int size_scale = 2;
 212   /* Maximal size of size_time_table before we start to be conservative.  */
 213   static const int max_size_time_table_size = 256;
 214 };
 215
 216 class GTY((user)) ipa_fn_summary_t:
 217   public fast_function_summary <ipa_fn_summary *, va_gc>
 218 {
 219 public:
 220   ipa_fn_summary_t (symbol_table *symtab):
 221     fast_function_summary <ipa_fn_summary *, va_gc> (symtab) {}
 222
 223   static ipa_fn_summary_t *create_ggc (symbol_table *symtab)
 224   {
 225     class ipa_fn_summary_t *summary
 226       = new (ggc_alloc_no_dtor<ipa_fn_summary_t> ()) ipa_fn_summary_t (symtab);
 227     summary->disable_insertion_hook ();
 228     return summary;
 229   }
 230
 231   /* Remove ipa_fn_summary for all callees of NODE.  */
 232   void remove_callees (cgraph_node *node);
 233
 234   virtual void insert (cgraph_node *, ipa_fn_summary *);
 235   virtual void remove (cgraph_node *node, ipa_fn_summary *)
 236   {
 237     remove_callees (node);
 238   }
 239
 240   virtual void duplicate (cgraph_node *src, cgraph_node *dst,
 241                           ipa_fn_summary *src_data, ipa_fn_summary *dst_data);
 242 };
 243
 244 extern GTY(()) fast_function_summary <ipa_fn_summary *, va_gc>
 245   *ipa_fn_summaries;
 246
 247 class ipa_size_summary_t:
 248   public fast_function_summary <ipa_size_summary *, va_heap>
 249 {
 250 public:
 251   ipa_size_summary_t (symbol_table *symtab):
 252     fast_function_summary <ipa_size_summary *, va_heap> (symtab)
 253   {
 254     disable_insertion_hook ();
 255   }
 256
 257   virtual void duplicate (cgraph_node *, cgraph_node *,
 258                           ipa_size_summary *src_data,
 259                           ipa_size_summary *dst_data)
 260   {
 261     *dst_data = *src_data;
 262   }
 263 };
 264 extern fast_function_summary <ipa_size_summary *, va_heap>
 265   *ipa_size_summaries;
 266
 267 /* Information kept about callgraph edges.  */
 268 class ipa_call_summary
 269 {
 270 public:
 271   /* Keep all field empty so summary dumping works during its computation.
 272      This is useful for debugging.  */
 273   ipa_call_summary ()
 274     : predicate (NULL), param (vNULL), call_stmt_size (0), call_stmt_time (0),
 275       loop_depth (0), is_return_callee_uncaptured (false)
 276     {
 277     }
 278
 279   /* Copy constructor.  */
 280   ipa_call_summary (const ipa_call_summary &s):
 281     predicate (s.predicate), param (s.param), call_stmt_size (s.call_stmt_size),
 282     call_stmt_time (s.call_stmt_time), loop_depth (s.loop_depth),
 283     is_return_callee_uncaptured (s.is_return_callee_uncaptured)
 284   {
 285   }
 286
 287   /* Default destructor.  */
 288   ~ipa_call_summary ();
 289
 290   ipa_predicate *predicate;
 291   /* Vector indexed by parameters.  */
 292   vec<inline_param_summary> param;
 293   /* Estimated size and time of the call statement.  */
 294   int call_stmt_size;
 295   int call_stmt_time;
 296   /* Depth of loop nest, 0 means no nesting.  */
 297   unsigned int loop_depth;
 298   /* Indicates whether the caller returns the value of it's callee.  */
 299   bool is_return_callee_uncaptured;
 300 };
 301
 302 class ipa_call_summary_t: public fast_call_summary <ipa_call_summary *, va_heap>
 303 {
 304 public:
 305   ipa_call_summary_t (symbol_table *symtab):
 306     fast_call_summary <ipa_call_summary *, va_heap> (symtab) {}
 307
 308   /* Hook that is called by summary when an edge is duplicated.  */
 309   virtual void duplicate (cgraph_edge *src, cgraph_edge *dst,
 310                           ipa_call_summary *src_data,
 311                           ipa_call_summary *dst_data);
 312 };
 313
 314 /* Estimated execution times, code sizes and other information about the
 315    code executing a call described by ipa_call_context.  */
 316
 317 struct ipa_call_estimates
 318 {
 319   /* Estimated size needed to execute call in the given context. */
 320   int size;
 321
 322   /* Minimal size needed for the call that is + independent on the call context
 323      and can be used for fast estimates.  */
 324   int min_size;
 325
 326   /* Estimated time needed to execute call in the given context. */
 327   sreal time;
 328
 329   /* Estimated time needed to execute the function when not ignoring
 330      computations known to be constant in this context.  */
 331   sreal nonspecialized_time;
 332
 333   /* Further discovered reasons why to inline or specialize the give calls.  */
 334   ipa_hints hints;
 335
 336   /* Frequency how often a loop with known number of iterations is encountered.
 337      Calculated with hints.  */
 338   sreal loops_with_known_iterations;
 339
 340   /* Frequency how often a loop with known strides is encountered.  Calculated
 341      with hints.  */
 342   sreal loops_with_known_strides;
 343 };
 344
 345 class ipa_cached_call_context;
 346
 347 /* This object describe a context of call.  That is a summary of known
 348    information about its parameters.  Main purpose of this context is
 349    to give more realistic estimations of function runtime, size and
 350    inline hints.  */
 351 class ipa_call_context
 352 {
 353 public:
 354   ipa_call_context (cgraph_node *node,
 355                     clause_t possible_truths,
 356                     clause_t nonspec_possible_truths,
 357                     vec<inline_param_summary> inline_param_summary,
 358                     ipa_auto_call_arg_values *arg_values);
 359   ipa_call_context ()
 360   : m_node(NULL)
 361   {
 362   }
 363   void estimate_size_and_time (ipa_call_estimates *estimates,
 364                                bool est_times = true, bool est_hints = true);
 365   bool equal_to (const ipa_call_context &);
 366   bool exists_p ()
 367   {
 368     return m_node != NULL;
 369   }
 370 private:
 371   /* Called function.  */
 372   cgraph_node *m_node;
 373   /* Clause describing what predicate conditionals can be satisfied
 374      in this context if function is inlined/specialized.  */
 375   clause_t m_possible_truths;
 376   /* Clause describing what predicate conditionals can be satisfied
 377      in this context if function is kept offline.  */
 378   clause_t m_nonspec_possible_truths;
 379   /* Inline summary maintains info about change probabilities.  */
 380   vec<inline_param_summary> m_inline_param_summary;
 381
 382   /* Even after having calculated clauses, the information about argument
 383      values is used to resolve indirect calls.  */
 384   ipa_call_arg_values m_avals;
 385
 386   friend ipa_cached_call_context;
 387 };
 388
 389 /* Variant of ipa_call_context that is stored in a cache over a longer period
 390    of time.  */
 391
 392 class ipa_cached_call_context : public ipa_call_context
 393 {
 394 public:
 395   void duplicate_from (const ipa_call_context &ctx);
 396   void release ();
 397 };
 398
 399 extern fast_call_summary <ipa_call_summary *, va_heap> *ipa_call_summaries;
 400
 401 /* In ipa-fnsummary.c  */
 402 void ipa_debug_fn_summary (struct cgraph_node *);
 403 void ipa_dump_fn_summaries (FILE *f);
 404 void ipa_dump_fn_summary (FILE *f, struct cgraph_node *node);
 405 void ipa_dump_hints (FILE *f, ipa_hints);
 406 void ipa_free_fn_summary (void);
 407 void ipa_free_size_summary (void);
 408 void inline_analyze_function (struct cgraph_node *node);
 409 void estimate_ipcp_clone_size_and_time (struct cgraph_node *node,
 410                                         ipa_auto_call_arg_values *avals,
 411                                         ipa_call_estimates *estimates);
 412 void ipa_merge_fn_summary_after_inlining (struct cgraph_edge *edge);
 413 void ipa_update_overall_fn_summary (struct cgraph_node *node, bool reset = true);
 414 void compute_fn_summary (struct cgraph_node *, bool);
 415 bool refs_local_or_readonly_memory_p (tree);
 416 bool points_to_local_or_readonly_memory_p (tree);
 417
 418
 419 void evaluate_properties_for_edge (struct cgraph_edge *e,
 420                                    bool inline_p,
 421                                    clause_t *clause_ptr,
 422                                    clause_t *nonspec_clause_ptr,
 423                                    ipa_auto_call_arg_values *avals,
 424                                    bool compute_contexts);
 425
 426 void ipa_fnsummary_c_finalize (void);
 427 HOST_WIDE_INT ipa_get_stack_frame_offset (struct cgraph_node *node);
 428 void ipa_remove_from_growth_caches (struct cgraph_edge *edge);
 429
 430 /* Return true if EDGE is a cross module call.  */
 431
 432 static inline bool
 433 cross_module_call_p (struct cgraph_edge *edge)
 434 {
 435   /* Here we do not want to walk to alias target becuase ICF may create
 436      cross-unit aliases.  */
 437   if (edge->caller->unit_id == edge->callee->unit_id)
 438     return false;
 439   /* If the call is to a (former) comdat function or s symbol with mutiple
 440      extern inline definitions then treat is as in-module call.  */
 441   if (edge->callee->merged_extern_inline || edge->callee->merged_comdat
 442       || DECL_COMDAT (edge->callee->decl))
 443     return false;
 444   return true;
 445 }
 446
 447 #endif /* GCC_IPA_FNSUMMARY_H */