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   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   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   class 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 predicate &, const predicate &,
 207                           bool call = false);
 208
 209   /* We keep values scaled up, so fractional sizes can be accounted.  */
 210   static const int size_scale = 2;
 211   /* Maximal size of size_time_table before we start to be conservative.  */
 212   static const int max_size_time_table_size = 256;
 213 };
 214
 215 class GTY((user)) ipa_fn_summary_t:
 216   public fast_function_summary <ipa_fn_summary *, va_gc>
 217 {
 218 public:
 219   ipa_fn_summary_t (symbol_table *symtab):
 220     fast_function_summary <ipa_fn_summary *, va_gc> (symtab) {}
 221
 222   static ipa_fn_summary_t *create_ggc (symbol_table *symtab)
 223   {
 224     class ipa_fn_summary_t *summary
 225       = new (ggc_alloc_no_dtor<ipa_fn_summary_t> ()) ipa_fn_summary_t (symtab);
 226     summary->disable_insertion_hook ();
 227     return summary;
 228   }
 229
 230   /* Remove ipa_fn_summary for all callees of NODE.  */
 231   void remove_callees (cgraph_node *node);
 232
 233   virtual void insert (cgraph_node *, ipa_fn_summary *);
 234   virtual void remove (cgraph_node *node, ipa_fn_summary *)
 235   {
 236     remove_callees (node);
 237   }
 238
 239   virtual void duplicate (cgraph_node *src, cgraph_node *dst,
 240                           ipa_fn_summary *src_data, ipa_fn_summary *dst_data);
 241 };
 242
 243 extern GTY(()) fast_function_summary <ipa_fn_summary *, va_gc>
 244   *ipa_fn_summaries;
 245
 246 class ipa_size_summary_t:
 247   public fast_function_summary <ipa_size_summary *, va_heap>
 248 {
 249 public:
 250   ipa_size_summary_t (symbol_table *symtab):
 251     fast_function_summary <ipa_size_summary *, va_heap> (symtab)
 252   {
 253     disable_insertion_hook ();
 254   }
 255
 256   virtual void duplicate (cgraph_node *, cgraph_node *,
 257                           ipa_size_summary *src_data,
 258                           ipa_size_summary *dst_data)
 259   {
 260     *dst_data = *src_data;
 261   }
 262 };
 263 extern fast_function_summary <ipa_size_summary *, va_heap>
 264   *ipa_size_summaries;
 265
 266 /* Information kept about callgraph edges.  */
 267 class ipa_call_summary
 268 {
 269 public:
 270   /* Keep all field empty so summary dumping works during its computation.
 271      This is useful for debugging.  */
 272   ipa_call_summary ()
 273     : predicate (NULL), param (vNULL), call_stmt_size (0), call_stmt_time (0),
 274       loop_depth (0), is_return_callee_uncaptured (false)
 275     {
 276     }
 277
 278   /* Copy constructor.  */
 279   ipa_call_summary (const ipa_call_summary &s):
 280     predicate (s.predicate), param (s.param), call_stmt_size (s.call_stmt_size),
 281     call_stmt_time (s.call_stmt_time), loop_depth (s.loop_depth),
 282     is_return_callee_uncaptured (s.is_return_callee_uncaptured)
 283   {
 284   }
 285
 286   /* Default destructor.  */
 287   ~ipa_call_summary ();
 288
 289   class predicate *predicate;
 290   /* Vector indexed by parameters.  */
 291   vec<inline_param_summary> param;
 292   /* Estimated size and time of the call statement.  */
 293   int call_stmt_size;
 294   int call_stmt_time;
 295   /* Depth of loop nest, 0 means no nesting.  */
 296   unsigned int loop_depth;
 297   /* Indicates whether the caller returns the value of it's callee.  */
 298   bool is_return_callee_uncaptured;
 299 };
 300
 301 class ipa_call_summary_t: public fast_call_summary <ipa_call_summary *, va_heap>
 302 {
 303 public:
 304   ipa_call_summary_t (symbol_table *symtab):
 305     fast_call_summary <ipa_call_summary *, va_heap> (symtab) {}
 306
 307   /* Hook that is called by summary when an edge is duplicated.  */
 308   virtual void duplicate (cgraph_edge *src, cgraph_edge *dst,
 309                           ipa_call_summary *src_data,
 310                           ipa_call_summary *dst_data);
 311 };
 312
 313 /* Estimated execution times, code sizes and other information about the
 314    code executing a call described by ipa_call_context.  */
 315
 316 struct ipa_call_estimates
 317 {
 318   /* Estimated size needed to execute call in the given context. */
 319   int size;
 320
 321   /* Minimal size needed for the call that is + independent on the call context
 322      and can be used for fast estimates.  */
 323   int min_size;
 324
 325   /* Estimated time needed to execute call in the given context. */
 326   sreal time;
 327
 328   /* Estimated time needed to execute the function when not ignoring
 329      computations known to be constant in this context.  */
 330   sreal nonspecialized_time;
 331
 332   /* Further discovered reasons why to inline or specialize the give calls.  */
 333   ipa_hints hints;
 334
 335   /* Frequency how often a loop with known number of iterations is encountered.
 336      Calculated with hints.  */
 337   sreal loops_with_known_iterations;
 338
 339   /* Frequency how often a loop with known strides is encountered.  Calculated
 340      with hints.  */
 341   sreal loops_with_known_strides;
 342 };
 343
 344 class ipa_cached_call_context;
 345
 346 /* This object describe a context of call.  That is a summary of known
 347    information about its parameters.  Main purpose of this context is
 348    to give more realistic estimations of function runtime, size and
 349    inline hints.  */
 350 class ipa_call_context
 351 {
 352 public:
 353   ipa_call_context (cgraph_node *node,
 354                     clause_t possible_truths,
 355                     clause_t nonspec_possible_truths,
 356                     vec<inline_param_summary> inline_param_summary,
 357                     ipa_auto_call_arg_values *arg_values);
 358   ipa_call_context ()
 359   : m_node(NULL)
 360   {
 361   }
 362   void estimate_size_and_time (ipa_call_estimates *estimates,
 363                                bool est_times = true, bool est_hints = true);
 364   bool equal_to (const ipa_call_context &);
 365   bool exists_p ()
 366   {
 367     return m_node != NULL;
 368   }
 369 private:
 370   /* Called function.  */
 371   cgraph_node *m_node;
 372   /* Clause describing what predicate conditionals can be satisfied
 373      in this context if function is inlined/specialized.  */
 374   clause_t m_possible_truths;
 375   /* Clause describing what predicate conditionals can be satisfied
 376      in this context if function is kept offline.  */
 377   clause_t m_nonspec_possible_truths;
 378   /* Inline summary maintains info about change probabilities.  */
 379   vec<inline_param_summary> m_inline_param_summary;
 380
 381   /* Even after having calculated clauses, the information about argument
 382      values is used to resolve indirect calls.  */
 383   ipa_call_arg_values m_avals;
 384
 385   friend ipa_cached_call_context;
 386 };
 387
 388 /* Variant of ipa_call_context that is stored in a cache over a longer period
 389    of time.  */
 390
 391 class ipa_cached_call_context : public ipa_call_context
 392 {
 393 public:
 394   void duplicate_from (const ipa_call_context &ctx);
 395   void release ();
 396 };
 397
 398 extern fast_call_summary <ipa_call_summary *, va_heap> *ipa_call_summaries;
 399
 400 /* In ipa-fnsummary.c  */
 401 void ipa_debug_fn_summary (struct cgraph_node *);
 402 void ipa_dump_fn_summaries (FILE *f);
 403 void ipa_dump_fn_summary (FILE *f, struct cgraph_node *node);
 404 void ipa_dump_hints (FILE *f, ipa_hints);
 405 void ipa_free_fn_summary (void);
 406 void ipa_free_size_summary (void);
 407 void inline_analyze_function (struct cgraph_node *node);
 408 void estimate_ipcp_clone_size_and_time (struct cgraph_node *node,
 409                                         ipa_auto_call_arg_values *avals,
 410                                         ipa_call_estimates *estimates);
 411 void ipa_merge_fn_summary_after_inlining (struct cgraph_edge *edge);
 412 void ipa_update_overall_fn_summary (struct cgraph_node *node, bool reset = true);
 413 void compute_fn_summary (struct cgraph_node *, bool);
 414 bool refs_local_or_readonly_memory_p (tree);
 415 bool points_to_local_or_readonly_memory_p (tree);
 416
 417
 418 void evaluate_properties_for_edge (struct cgraph_edge *e,
 419                                    bool inline_p,
 420                                    clause_t *clause_ptr,
 421                                    clause_t *nonspec_clause_ptr,
 422                                    ipa_auto_call_arg_values *avals,
 423                                    bool compute_contexts);
 424
 425 void ipa_fnsummary_c_finalize (void);
 426 HOST_WIDE_INT ipa_get_stack_frame_offset (struct cgraph_node *node);
 427 void ipa_remove_from_growth_caches (struct cgraph_edge *edge);
 428
 429 /* Return true if EDGE is a cross module call.  */
 430
 431 static inline bool
 432 cross_module_call_p (struct cgraph_edge *edge)
 433 {
 434   /* Here we do not want to walk to alias target becuase ICF may create
 435      cross-unit aliases.  */
 436   if (edge->caller->unit_id == edge->callee->unit_id)
 437     return false;
 438   /* If the call is to a (former) comdat function or s symbol with mutiple
 439      extern inline definitions then treat is as in-module call.  */
 440   if (edge->callee->merged_extern_inline || edge->callee->merged_comdat
 441       || DECL_COMDAT (edge->callee->decl))
 442     return false;
 443   return true;
 444 }
 445
 446 #endif /* GCC_IPA_FNSUMMARY_H */