gcc/params.def

   1 /* params.def - Run-time parameters.
   2    Copyright (C) 2001, 2002, 2004, 2005 Free Software Foundation, Inc.
   3    Written by Mark Mitchell <mark@codesourcery.com>.
   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 2, 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 COPYING.  If not, write to the Free
  19 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  20 02110-1301, USA.
  21
  22 */
  23
  24 /* This file contains definitions for language-independent
  25    parameters.  The DEFPARAM macro takes 6 arguments:
  26
  27      - The enumeral corresponding to this parameter.
  28
  29      - The name that can be used to set this parameter using the
  30        command-line option `--param <name>=<value>'.
  31
  32      - A help string explaining how the parameter is used.
  33
  34      - A default value for the parameter.
  35
  36      - The minimum acceptable value for the parameter.
  37
  38      - The maximum acceptable value for the parameter (if greater than
  39      the minimum).
  40
  41    Be sure to add an entry to invoke.texi summarizing the parameter.  */
  42
  43 /* The maximum number of fields in a variable with only implicit uses
  44    for which structure aliasing will consider trying to track each
  45    field.  The default is 5.  */
  46 DEFPARAM (PARAM_SALIAS_MAX_IMPLICIT_FIELDS,
  47           "salias-max-implicit-fields",
  48           "The maximum number of fields in a structure variable without direct structure accesses that GCC will attempt to track separately",
  49           5, 0, 0)
  50
  51 /* The maximum structure size at which the scalar replacement of
  52    aggregates (SRA) pass will perform block copies.  The default
  53    value, 0, implies that GCC will select the most appropriate size
  54    itself.  */
  55 DEFPARAM (PARAM_SRA_MAX_STRUCTURE_SIZE,
  56           "sra-max-structure-size",
  57           "The maximum structure size (in bytes) for which GCC will "
  58           "use by-element copies",
  59           0, 0, 0)
  60
  61 /* The maximum number of structure fields which the SRA pass will
  62    instantiate to avoid block copies.  The default value, 0, implies
  63    that GCC will select the appropriate value itself.  */
  64 DEFPARAM (PARAM_SRA_MAX_STRUCTURE_COUNT,
  65           "sra-max-structure-count",
  66           "The maximum number of structure fields for which GCC will "
  67           "use by-element copies",
  68           0, 0, 0)
  69
  70 /* The ratio between instantiated fields and the complete structure
  71    size.  We say that if the ratio of the number of bytes in
  72    instantiated fields to the number of bytes in the complete
  73    structure exceeds this parameter, or if the number of instantiated
  74    fields to the total number of fields exceeds this parameter, then
  75    block copies are not used.  The default is 75%.  */
  76 DEFPARAM (PARAM_SRA_FIELD_STRUCTURE_RATIO,
  77           "sra-field-structure-ratio",
  78           "The threshold ratio between instantiated fields and the total structure size",
  79           75, 0, 100)
  80
  81 /* The single function inlining limit. This is the maximum size
  82    of a function counted in internal gcc instructions (not in
  83    real machine instructions) that is eligible for inlining
  84    by the tree inliner.
  85    The default value is 450.
  86    Only functions marked inline (or methods defined in the class
  87    definition for C++) are affected by this.
  88    There are more restrictions to inlining: If inlined functions
  89    call other functions, the already inlined instructions are
  90    counted and once the recursive inline limit (see
  91    "max-inline-insns" parameter) is exceeded, the acceptable size
  92    gets decreased.  */
  93 DEFPARAM (PARAM_MAX_INLINE_INSNS_SINGLE,
  94           "max-inline-insns-single",
  95           "The maximum number of instructions in a single function eligible for inlining",
  96           450, 0, 0)
  97
  98 /* The single function inlining limit for functions that are
  99    inlined by virtue of -finline-functions (-O3).
 100    This limit should be chosen to be below or equal to the limit
 101    that is applied to functions marked inlined (or defined in the
 102    class declaration in C++) given by the "max-inline-insns-single"
 103    parameter.
 104    The default value is 90.  */
 105 DEFPARAM (PARAM_MAX_INLINE_INSNS_AUTO,
 106           "max-inline-insns-auto",
 107           "The maximum number of instructions when automatically inlining",
 108           90, 0, 0)
 109
 110 DEFPARAM (PARAM_MAX_INLINE_INSNS_RECURSIVE,
 111           "max-inline-insns-recursive",
 112           "The maximum number of instructions inline function can grow to via recursive inlining",
 113           450, 0, 0)
 114
 115 DEFPARAM (PARAM_MAX_INLINE_INSNS_RECURSIVE_AUTO,
 116           "max-inline-insns-recursive-auto",
 117           "The maximum number of instructions non-inline function can grow to via recursive inlining",
 118           450, 0, 0)
 119
 120 DEFPARAM (PARAM_MAX_INLINE_RECURSIVE_DEPTH,
 121           "max-inline-recursive-depth",
 122           "The maximum depth of recursive inlining for inline functions",
 123           8, 0, 0)
 124
 125 DEFPARAM (PARAM_MAX_INLINE_RECURSIVE_DEPTH_AUTO,
 126           "max-inline-recursive-depth-auto",
 127           "The maximum depth of recursive inlining for non-inline functions",
 128           8, 0, 0)
 129
 130 DEFPARAM (PARAM_MIN_INLINE_RECURSIVE_PROBABILITY,
 131           "min-inline-recursive-probability",
 132           "Inline recursively only when the probability of call being executed exceeds the parameter",
 133           10, 0, 0)
 134
 135 /* Limit the number of expansions created by the variable expansion
 136    optimization to avoid register pressure.  */
 137 DEFPARAM (PARAM_MAX_VARIABLE_EXPANSIONS,
 138           "max-variable-expansions-in-unroller",
 139           "If -fvariable-expansion-in-unroller is used, the maximum number of times that an individual variable will be expanded during loop unrolling",
 140           1, 0, 0)
 141
 142 /* The maximum number of instructions to consider when looking for an
 143    instruction to fill a delay slot.  If more than this arbitrary
 144    number of instructions is searched, the time savings from filling
 145    the delay slot will be minimal so stop searching.  Increasing
 146    values mean more aggressive optimization, making the compile time
 147    increase with probably small improvement in executable run time.  */
 148 DEFPARAM (PARAM_MAX_DELAY_SLOT_INSN_SEARCH,
 149           "max-delay-slot-insn-search",
 150           "The maximum number of instructions to consider to fill a delay slot",
 151           100, 0, 0)
 152
 153 /* When trying to fill delay slots, the maximum number of instructions
 154    to consider when searching for a block with valid live register
 155    information.  Increasing this arbitrarily chosen value means more
 156    aggressive optimization, increasing the compile time.  This
 157    parameter should be removed when the delay slot code is rewritten
 158    to maintain the control-flow graph.  */
 159 DEFPARAM(PARAM_MAX_DELAY_SLOT_LIVE_SEARCH,
 160          "max-delay-slot-live-search",
 161          "The maximum number of instructions to consider to find accurate live register information",
 162          333, 0, 0)
 163
 164 /* This parameter limits the number of branch elements that the
 165    scheduler will track anti-dependencies through without resetting
 166    the tracking mechanism.  Large functions with few calls or barriers
 167    can generate lists containing many 1000's of dependencies.  Generally
 168    the compiler either uses all available memory, or runs for far too long.  */
 169 DEFPARAM(PARAM_MAX_PENDING_LIST_LENGTH,
 170          "max-pending-list-length",
 171          "The maximum length of scheduling's pending operations list",
 172          32, 0, 0)
 173
 174 DEFPARAM(PARAM_LARGE_FUNCTION_INSNS,
 175          "large-function-insns",
 176          "The size of function body to be considered large",
 177          2700, 0, 0)
 178 DEFPARAM(PARAM_LARGE_FUNCTION_GROWTH,
 179          "large-function-growth",
 180          "Maximal growth due to inlining of large function (in percent)",
 181          100, 0, 0)
 182 DEFPARAM(PARAM_INLINE_UNIT_GROWTH,
 183          "inline-unit-growth",
 184          "how much can given compilation unit grow because of the inlining (in percent)",
 185          50, 0, 0)
 186 DEFPARAM(PARAM_INLINE_CALL_COST,
 187          "inline-call-cost",
 188          "expense of call operation relative to ordinary arithmetic operations",
 189          16, 0, 0)
 190
 191 /* The GCSE optimization will be disabled if it would require
 192    significantly more memory than this value.  */
 193 DEFPARAM(PARAM_MAX_GCSE_MEMORY,
 194          "max-gcse-memory",
 195          "The maximum amount of memory to be allocated by GCSE",
 196          50 * 1024 * 1024, 0, 0)
 197 /* The number of repetitions of copy/const prop and PRE to run.  */
 198 DEFPARAM(PARAM_MAX_GCSE_PASSES,
 199         "max-gcse-passes",
 200         "The maximum number of passes to make when doing GCSE",
 201         1, 1, 0)
 202 /* This is the threshold ratio when to perform partial redundancy
 203    elimination after reload. We perform partial redundancy elimination
 204    when the following holds:
 205    (Redundant load execution count)
 206    ------------------------------- >= GCSE_AFTER_RELOAD_PARTIAL_FRACTION
 207    (Added loads execution count)                                          */
 208 DEFPARAM(PARAM_GCSE_AFTER_RELOAD_PARTIAL_FRACTION,
 209         "gcse-after-reload-partial-fraction",
 210         "The threshold ratio for performing partial redundancy elimination after reload",
 211         3, 0, 0)
 212 /* This is the threshold ratio of the critical edges execution count compared to
 213    the redundant loads execution count that permits performing the load
 214    redundancy elimination in gcse after reload.  */
 215 DEFPARAM(PARAM_GCSE_AFTER_RELOAD_CRITICAL_FRACTION,
 216         "gcse-after-reload-critical-fraction",
 217         "The threshold ratio of critical edges execution count that permit performing redundancy elimination after reload",
 218         10, 0, 0)
 219 /* This parameter limits the number of insns in a loop that will be unrolled,
 220    and by how much the loop is unrolled.
 221
 222    This limit should be at most half of the peeling limits:  loop unroller
 223    decides to not unroll loops that iterate fewer than 2*number of allowed
 224    unrollings and thus we would have loops that are neither peeled or unrolled
 225    otherwise.  */
 226 DEFPARAM(PARAM_MAX_UNROLLED_INSNS,
 227          "max-unrolled-insns",
 228          "The maximum number of instructions to consider to unroll in a loop",
 229          200, 0, 0)
 230 /* This parameter limits how many times the loop is unrolled depending
 231    on number of insns really executed in each iteration.  */
 232 DEFPARAM(PARAM_MAX_AVERAGE_UNROLLED_INSNS,
 233          "max-average-unrolled-insns",
 234          "The maximum number of instructions to consider to unroll in a loop on average",
 235          80, 0, 0)
 236 /* The maximum number of unrollings of a single loop.  */
 237 DEFPARAM(PARAM_MAX_UNROLL_TIMES,
 238         "max-unroll-times",
 239         "The maximum number of unrollings of a single loop",
 240         8, 0, 0)
 241 /* The maximum number of insns of a peeled loop.  */
 242 DEFPARAM(PARAM_MAX_PEELED_INSNS,
 243         "max-peeled-insns",
 244         "The maximum number of insns of a peeled loop",
 245         400, 0, 0)
 246 /* The maximum number of peelings of a single loop.  */
 247 DEFPARAM(PARAM_MAX_PEEL_TIMES,
 248         "max-peel-times",
 249         "The maximum number of peelings of a single loop",
 250         16, 0, 0)
 251 /* The maximum number of insns of a peeled loop.  */
 252 DEFPARAM(PARAM_MAX_COMPLETELY_PEELED_INSNS,
 253         "max-completely-peeled-insns",
 254         "The maximum number of insns of a completely peeled loop",
 255         400, 0, 0)
 256 /* The maximum number of peelings of a single loop that is peeled completely.  */
 257 DEFPARAM(PARAM_MAX_COMPLETELY_PEEL_TIMES,
 258         "max-completely-peel-times",
 259         "The maximum number of peelings of a single loop that is peeled completely",
 260         16, 0, 0)
 261 /* The maximum number of insns of a peeled loop that rolls only once.  */
 262 DEFPARAM(PARAM_MAX_ONCE_PEELED_INSNS,
 263         "max-once-peeled-insns",
 264         "The maximum number of insns of a peeled loop that rolls only once",
 265         400, 0, 0)
 266
 267 /* The maximum number of insns of an unswitched loop.  */
 268 DEFPARAM(PARAM_MAX_UNSWITCH_INSNS,
 269         "max-unswitch-insns",
 270         "The maximum number of insns of an unswitched loop",
 271         50, 0, 0)
 272 /* The maximum level of recursion in unswitch_single_loop.  */
 273 DEFPARAM(PARAM_MAX_UNSWITCH_LEVEL,
 274         "max-unswitch-level",
 275         "The maximum number of unswitchings in a single loop",
 276         3, 0, 0)
 277
 278 /* The maximum number of iterations of a loop the brute force algorithm
 279    for analysis of # of iterations of the loop tries to evaluate.  */
 280 DEFPARAM(PARAM_MAX_ITERATIONS_TO_TRACK,
 281         "max-iterations-to-track",
 282         "Bound on the number of iterations the brute force # of iterations analysis algorithm evaluates",
 283         1000, 0, 0)
 284
 285 DEFPARAM(PARAM_MAX_SMS_LOOP_NUMBER,
 286          "max-sms-loop-number",
 287          "Maximum number of loops to perform swing modulo scheduling on (mainly for debugging)",
 288          -1, -1, -1)
 289
 290 /* This parameter is used to tune SMS MAX II calculations.  */
 291 DEFPARAM(PARAM_SMS_MAX_II_FACTOR,
 292          "sms-max-ii-factor",
 293          "A factor for tuning the upper bound that swing modulo scheduler uses for scheduling a loop",
 294          100, 0, 0)
 295 DEFPARAM(PARAM_SMS_DFA_HISTORY,
 296          "sms-dfa-history",
 297          "The number of cycles the swing modulo scheduler considers when checking conflicts using DFA",
 298          0, 0, 0)
 299 DEFPARAM(PARAM_SMS_LOOP_AVERAGE_COUNT_THRESHOLD,
 300          "sms-loop-average-count-threshold",
 301          "A threshold on the average loop count considered by the swing modulo scheduler",
 302          0, 0, 0)
 303
 304 DEFPARAM(HOT_BB_COUNT_FRACTION,
 305          "hot-bb-count-fraction",
 306          "Select fraction of the maximal count of repetitions of basic block in program given basic block needs to have to be considered hot",
 307          10000, 0, 0)
 308 DEFPARAM(HOT_BB_FREQUENCY_FRACTION,
 309          "hot-bb-frequency-fraction",
 310          "Select fraction of the maximal frequency of executions of basic block in function given basic block needs to have to be considered hot",
 311          1000, 0, 0)
 312
 313 /* For guessed profiles, the loops having unknown number of iterations
 314    are predicted to iterate relatively few (10) times at average.
 315    For functions containing one loop with large known number of iterations
 316    and other loops having unbounded loops we would end up predicting all
 317    the other loops cold that is not usually the case.  So we need to artificially
 318    flatten the profile.
 319
 320    We need to cut the maximal predicted iterations to large enought iterations
 321    so the loop appears important, but safely within HOT_BB_COUNT_FRACTION
 322    range.  */
 323
 324 DEFPARAM(PARAM_MAX_PREDICTED_ITERATIONS,
 325          "max-predicted-iterations",
 326          "The maximum number of loop iterations we predict statically",
 327          100, 0, 0)
 328 DEFPARAM(TRACER_DYNAMIC_COVERAGE_FEEDBACK,
 329          "tracer-dynamic-coverage-feedback",
 330          "The percentage of function, weighted by execution frequency, that must be covered by trace formation. Used when profile feedback is available",
 331          95, 0, 100)
 332 DEFPARAM(TRACER_DYNAMIC_COVERAGE,
 333          "tracer-dynamic-coverage",
 334          "The percentage of function, weighted by execution frequency, that must be covered by trace formation. Used when profile feedback is not available",
 335          75, 0, 100)
 336 DEFPARAM(TRACER_MAX_CODE_GROWTH,
 337          "tracer-max-code-growth",
 338          "Maximal code growth caused by tail duplication (in percent)",
 339          100, 0, 0)
 340 DEFPARAM(TRACER_MIN_BRANCH_RATIO,
 341          "tracer-min-branch-ratio",
 342          "Stop reverse growth if the reverse probability of best edge is less than this threshold (in percent)",
 343          10, 0, 100)
 344 DEFPARAM(TRACER_MIN_BRANCH_PROBABILITY_FEEDBACK,
 345          "tracer-min-branch-probability-feedback",
 346          "Stop forward growth if the probability of best edge is less than this threshold (in percent). Used when profile feedback is available",
 347          80, 0, 100)
 348 DEFPARAM(TRACER_MIN_BRANCH_PROBABILITY,
 349          "tracer-min-branch-probability",
 350          "Stop forward growth if the probability of best edge is less than this threshold (in percent). Used when profile feedback is not available",
 351          50, 0, 100)
 352
 353 /* The maximum number of incoming edges to consider for crossjumping.  */
 354 DEFPARAM(PARAM_MAX_CROSSJUMP_EDGES,
 355          "max-crossjump-edges",
 356          "The maximum number of incoming edges to consider for crossjumping",
 357          100, 0, 0)
 358
 359 /* The minimum number of matching instructions to consider for crossjumping.  */
 360 DEFPARAM(PARAM_MIN_CROSSJUMP_INSNS,
 361      "min-crossjump-insns",
 362      "The minimum number of matching instructions to consider for crossjumping",
 363      5, 0, 0)
 364
 365 /* The maximum number expansion factor when copying basic blocks.  */
 366 DEFPARAM(PARAM_MAX_GROW_COPY_BB_INSNS,
 367      "max-grow-copy-bb-insns",
 368      "The maximum expansion factor when copying basic blocks",
 369      8, 0, 0)
 370
 371 /* The maximum number of insns to duplicate when unfactoring computed gotos.  */
 372 DEFPARAM(PARAM_MAX_GOTO_DUPLICATION_INSNS,
 373      "max-goto-duplication-insns",
 374      "The maximum number of insns to duplicate when unfactoring computed gotos",
 375      8, 0, 0)
 376
 377 /* The maximum length of path considered in cse.  */
 378 DEFPARAM(PARAM_MAX_CSE_PATH_LENGTH,
 379          "max-cse-path-length",
 380          "The maximum length of path considered in cse",
 381          10, 0, 0)
 382 DEFPARAM(PARAM_MAX_CSE_INSNS,
 383          "max-flow-memory-locations",
 384          "The maximum instructions CSE process before flushing",
 385          1000, 0, 0)
 386
 387 /* The cost of expression in loop invariant motion that is considered
 388    expensive.  */
 389 DEFPARAM(PARAM_LIM_EXPENSIVE,
 390          "lim-expensive",
 391          "The minimum cost of an expensive expression in the loop invariant motion",
 392          20, 0, 0)
 393
 394 /* Bound on number of candidates for induction variables below that
 395    all candidates are considered for each use in induction variable
 396    optimizations.  */
 397
 398 DEFPARAM(PARAM_IV_CONSIDER_ALL_CANDIDATES_BOUND,
 399          "iv-consider-all-candidates-bound",
 400          "Bound on number of candidates below that all candidates are considered in iv optimizations",
 401          30, 0, 0)
 402
 403 /* The induction variable optimizations give up on loops that contain more
 404    induction variable uses.  */
 405
 406 DEFPARAM(PARAM_IV_MAX_CONSIDERED_USES,
 407          "iv-max-considered-uses",
 408          "Bound on number of iv uses in loop optimized in iv optimizations",
 409          250, 0, 0)
 410
 411 /* If there are at most this number of ivs in the set, try removing unnecessary
 412    ivs from the set always.  */
 413
 414 DEFPARAM(PARAM_IV_ALWAYS_PRUNE_CAND_SET_BOUND,
 415          "iv-always-prune-cand-set-bound",
 416          "If number of candidates in the set is smaller, we always try to remove unused ivs during its optimization",
 417          10, 0, 0)
 418
 419 DEFPARAM(PARAM_SCEV_MAX_EXPR_SIZE,
 420          "scev-max-expr-size",
 421          "Bound on size of expressions used in the scalar evolutions analyzer",
 422          20, 0, 0)
 423
 424 DEFPARAM(PARAM_VECT_MAX_VERSION_CHECKS,
 425          "vect-max-version-checks",
 426          "Bound on number of runtime checks inserted by the vectorizer's loop versioning",
 427          6, 0, 0)
 428
 429 /* The product of the next two is used to decide whether or not to
 430    use .GLOBAL_VAR.  See tree-dfa.c.  */
 431 DEFPARAM(PARAM_GLOBAL_VAR_THRESHOLD,
 432         "global-var-threshold",
 433         "Given N calls and V call-clobbered vars in a function.  Use .GLOBAL_VAR if NxV is larger than this limit",
 434         500000, 0, 0)
 435
 436 DEFPARAM(PARAM_MAX_CSELIB_MEMORY_LOCATIONS,
 437          "max-cselib-memory-locations",
 438          "The maximum memory locations recorded by cselib",
 439          500, 0, 0)
 440 DEFPARAM(PARAM_MAX_FLOW_MEMORY_LOCATIONS,
 441          "max-flow-memory-locations",
 442          "The maximum memory locations recorded by flow",
 443          100, 0, 0)
 444
 445 #ifdef ENABLE_GC_ALWAYS_COLLECT
 446 # define GGC_MIN_EXPAND_DEFAULT 0
 447 # define GGC_MIN_HEAPSIZE_DEFAULT 0
 448 #else
 449 # define GGC_MIN_EXPAND_DEFAULT 30
 450 # define GGC_MIN_HEAPSIZE_DEFAULT 4096
 451 #endif
 452
 453 DEFPARAM(GGC_MIN_EXPAND,
 454          "ggc-min-expand",
 455          "Minimum heap expansion to trigger garbage collection, as a percentage of the total size of the heap",
 456          GGC_MIN_EXPAND_DEFAULT, 0, 0)
 457
 458 DEFPARAM(GGC_MIN_HEAPSIZE,
 459          "ggc-min-heapsize",
 460          "Minimum heap size before we start collecting garbage, in kilobytes",
 461          GGC_MIN_HEAPSIZE_DEFAULT, 0, 0)
 462
 463 #undef GGC_MIN_EXPAND_DEFAULT
 464 #undef GGC_MIN_HEAPSIZE_DEFAULT
 465
 466 DEFPARAM(PARAM_MAX_RELOAD_SEARCH_INSNS,
 467          "max-reload-search-insns",
 468          "The maximum number of instructions to search backward when looking for equivalent reload",
 469          100, 0, 0)
 470
 471 DEFPARAM(PARAM_MAX_ALIASED_VOPS,
 472          "max-aliased-vops",
 473          "The maximum number of virtual operands allowed to represent aliases before triggering alias grouping",
 474          500, 0, 0)
 475
 476 DEFPARAM(PARAM_MAX_SCHED_REGION_BLOCKS,
 477          "max-sched-region-blocks",
 478          "The maximum number of blocks in a region to be considered for interblock scheduling",
 479          10, 0, 0)
 480
 481 DEFPARAM(PARAM_MAX_SCHED_REGION_INSNS,
 482          "max-sched-region-insns",
 483          "The maximum number of insns in a region to be considered for interblock scheduling",
 484          100, 0, 0)
 485
 486 DEFPARAM(PARAM_MIN_SPEC_PROB,
 487          "min-spec-prob",
 488          "The minimum probability of reaching a source block for interblock speculative scheduling",
 489          40, 0, 0)
 490
 491 DEFPARAM(PARAM_MAX_LAST_VALUE_RTL,
 492          "max-last-value-rtl",
 493          "The maximum number of RTL nodes that can be recorded as combiner's last value",
 494          10000, 0, 0)
 495
 496 /* INTEGER_CST nodes are shared for values [{-1,0} .. N) for
 497    {signed,unsigned} integral types.  This determines N.
 498    Experimentation shows 256 to be a good value.  */
 499 DEFPARAM (PARAM_INTEGER_SHARE_LIMIT,
 500           "integer-share-limit",
 501           "The upper bound for sharing integer constants",
 502           256, 2, 2)
 503
 504 /* Incremental SSA updates for virtual operands may be very slow if
 505    there is a large number of mappings to process.  In those cases, it
 506    is faster to rewrite the virtual symbols from scratch as if they
 507    had been recently introduced.  This heuristic cannot be applied to
 508    SSA mappings for real SSA names, only symbols kept in FUD chains.
 509
 510    PARAM_MIN_VIRTUAL_MAPPINGS specifies the minimum number of virtual
 511    mappings that should be registered to trigger the heuristic.
 512
 513    PARAM_VIRTUAL_MAPPINGS_TO_SYMS_RATIO specifies the ratio between
 514    mappings and symbols.  If the number of virtual mappings is
 515    PARAM_VIRTUAL_MAPPINGS_TO_SYMS_RATIO bigger than the number of
 516    virtual symbols to be updated, then the updater switches to a full
 517    update for those symbols.  */
 518 DEFPARAM (PARAM_MIN_VIRTUAL_MAPPINGS,
 519           "min-virtual-mappings",
 520           "Minimum number of virtual mappings to consider switching to full virtual renames",
 521           100, 0, 0)
 522
 523 DEFPARAM (PARAM_VIRTUAL_MAPPINGS_TO_SYMS_RATIO,
 524           "virtual-mappings-ratio",
 525           "Ratio between virtual mappings and virtual symbols to do full virtual renames",
 526           3, 0, 0)
 527
 528 DEFPARAM (PARAM_SSP_BUFFER_SIZE,
 529           "ssp-buffer-size",
 530           "The lower bound for a buffer to be considered for stack smashing protection",
 531           8, 1, 0)
 532
 533 /* When we thread through a block we have to make copies of the
 534    statements within the block.  Clearly for large blocks the code
 535    duplication is bad.
 536
 537    PARAM_MAX_JUMP_THREAD_DUPLICATION_STMTS specifies the maximum number
 538    of statements and PHI nodes allowed in a block which is going to
 539    be duplicated for thread jumping purposes.
 540
 541    Some simple analysis showed that more than 99% of the jump
 542    threading opportunities are for blocks with less than 15
 543    statements.  So we can get the benefits of jump threading
 544    without excessive code bloat for pathological cases with the
 545    throttle set at 15 statements.  */
 546 DEFPARAM (PARAM_MAX_JUMP_THREAD_DUPLICATION_STMTS,
 547           "max-jump-thread-duplication-stmts",
 548           "Maximum number of statements allowed in a block that needs to be duplicated when threading jumps",
 549           15, 0, 0)
 550
 551 /*
 552 Local variables:
 553 mode:c
 554 End: */