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 number of array elements structure aliasing will decompose
  52    an array for.  The default is 4.  */
  53 DEFPARAM (PARAM_SALIAS_MAX_ARRAY_ELEMENTS,
  54           "salias-max-array-elements",
  55           "The maximum number of elements in an array for wich we track its elements separately",
  56           4, 0, 0)
  57
  58 /* The maximum structure size at which the scalar replacement of
  59    aggregates (SRA) pass will perform block copies.  The default
  60    value, 0, implies that GCC will select the most appropriate size
  61    itself.  */
  62 DEFPARAM (PARAM_SRA_MAX_STRUCTURE_SIZE,
  63           "sra-max-structure-size",
  64           "The maximum structure size (in bytes) for which GCC will "
  65           "use by-element copies",
  66           0, 0, 0)
  67
  68 /* The maximum number of structure fields which the SRA pass will
  69    instantiate to avoid block copies.  The default value, 0, implies
  70    that GCC will select the appropriate value itself.  */
  71 DEFPARAM (PARAM_SRA_MAX_STRUCTURE_COUNT,
  72           "sra-max-structure-count",
  73           "The maximum number of structure fields for which GCC will "
  74           "use by-element copies",
  75           0, 0, 0)
  76
  77 /* The ratio between instantiated fields and the complete structure
  78    size.  We say that if the ratio of the number of bytes in
  79    instantiated fields to the number of bytes in the complete
  80    structure exceeds this parameter, or if the number of instantiated
  81    fields to the total number of fields exceeds this parameter, then
  82    block copies are not used.  The default is 75%.  */
  83 DEFPARAM (PARAM_SRA_FIELD_STRUCTURE_RATIO,
  84           "sra-field-structure-ratio",
  85           "The threshold ratio between instantiated fields and the total structure size",
  86           75, 0, 100)
  87
  88 /* The single function inlining limit. This is the maximum size
  89    of a function counted in internal gcc instructions (not in
  90    real machine instructions) that is eligible for inlining
  91    by the tree inliner.
  92    The default value is 450.
  93    Only functions marked inline (or methods defined in the class
  94    definition for C++) are affected by this.
  95    There are more restrictions to inlining: If inlined functions
  96    call other functions, the already inlined instructions are
  97    counted and once the recursive inline limit (see
  98    "max-inline-insns" parameter) is exceeded, the acceptable size
  99    gets decreased.  */
 100 DEFPARAM (PARAM_MAX_INLINE_INSNS_SINGLE,
 101           "max-inline-insns-single",
 102           "The maximum number of instructions in a single function eligible for inlining",
 103           450, 0, 0)
 104
 105 /* The single function inlining limit for functions that are
 106    inlined by virtue of -finline-functions (-O3).
 107    This limit should be chosen to be below or equal to the limit
 108    that is applied to functions marked inlined (or defined in the
 109    class declaration in C++) given by the "max-inline-insns-single"
 110    parameter.
 111    The default value is 90.  */
 112 DEFPARAM (PARAM_MAX_INLINE_INSNS_AUTO,
 113           "max-inline-insns-auto",
 114           "The maximum number of instructions when automatically inlining",
 115           90, 0, 0)
 116
 117 DEFPARAM (PARAM_MAX_INLINE_INSNS_RECURSIVE,
 118           "max-inline-insns-recursive",
 119           "The maximum number of instructions inline function can grow to via recursive inlining",
 120           450, 0, 0)
 121
 122 DEFPARAM (PARAM_MAX_INLINE_INSNS_RECURSIVE_AUTO,
 123           "max-inline-insns-recursive-auto",
 124           "The maximum number of instructions non-inline function can grow to via recursive inlining",
 125           450, 0, 0)
 126
 127 DEFPARAM (PARAM_MAX_INLINE_RECURSIVE_DEPTH,
 128           "max-inline-recursive-depth",
 129           "The maximum depth of recursive inlining for inline functions",
 130           8, 0, 0)
 131
 132 DEFPARAM (PARAM_MAX_INLINE_RECURSIVE_DEPTH_AUTO,
 133           "max-inline-recursive-depth-auto",
 134           "The maximum depth of recursive inlining for non-inline functions",
 135           8, 0, 0)
 136
 137 DEFPARAM (PARAM_MIN_INLINE_RECURSIVE_PROBABILITY,
 138           "min-inline-recursive-probability",
 139           "Inline recursively only when the probability of call being executed exceeds the parameter",
 140           10, 0, 0)
 141
 142 /* Limit the number of expansions created by the variable expansion
 143    optimization to avoid register pressure.  */
 144 DEFPARAM (PARAM_MAX_VARIABLE_EXPANSIONS,
 145           "max-variable-expansions-in-unroller",
 146           "If -fvariable-expansion-in-unroller is used, the maximum number of times that an individual variable will be expanded during loop unrolling",
 147           1, 0, 0)
 148
 149 /* The maximum number of instructions to consider when looking for an
 150    instruction to fill a delay slot.  If more than this arbitrary
 151    number of instructions is searched, the time savings from filling
 152    the delay slot will be minimal so stop searching.  Increasing
 153    values mean more aggressive optimization, making the compile time
 154    increase with probably small improvement in executable run time.  */
 155 DEFPARAM (PARAM_MAX_DELAY_SLOT_INSN_SEARCH,
 156           "max-delay-slot-insn-search",
 157           "The maximum number of instructions to consider to fill a delay slot",
 158           100, 0, 0)
 159
 160 /* When trying to fill delay slots, the maximum number of instructions
 161    to consider when searching for a block with valid live register
 162    information.  Increasing this arbitrarily chosen value means more
 163    aggressive optimization, increasing the compile time.  This
 164    parameter should be removed when the delay slot code is rewritten
 165    to maintain the control-flow graph.  */
 166 DEFPARAM(PARAM_MAX_DELAY_SLOT_LIVE_SEARCH,
 167          "max-delay-slot-live-search",
 168          "The maximum number of instructions to consider to find accurate live register information",
 169          333, 0, 0)
 170
 171 /* This parameter limits the number of branch elements that the
 172    scheduler will track anti-dependencies through without resetting
 173    the tracking mechanism.  Large functions with few calls or barriers
 174    can generate lists containing many 1000's of dependencies.  Generally
 175    the compiler either uses all available memory, or runs for far too long.  */
 176 DEFPARAM(PARAM_MAX_PENDING_LIST_LENGTH,
 177          "max-pending-list-length",
 178          "The maximum length of scheduling's pending operations list",
 179          32, 0, 0)
 180
 181 DEFPARAM(PARAM_LARGE_FUNCTION_INSNS,
 182          "large-function-insns",
 183          "The size of function body to be considered large",
 184          2700, 0, 0)
 185 DEFPARAM(PARAM_LARGE_FUNCTION_GROWTH,
 186          "large-function-growth",
 187          "Maximal growth due to inlining of large function (in percent)",
 188          100, 0, 0)
 189 DEFPARAM(PARAM_LARGE_UNIT_INSNS,
 190          "large-unit-insns",
 191          "The size of translation unit to be considered large",
 192          10000, 0, 0)
 193 DEFPARAM(PARAM_INLINE_UNIT_GROWTH,
 194          "inline-unit-growth",
 195          "how much can given compilation unit grow because of the inlining (in percent)",
 196          50, 0, 0)
 197 DEFPARAM(PARAM_INLINE_CALL_COST,
 198          "inline-call-cost",
 199          "expense of call operation relative to ordinary arithmetic operations",
 200          16, 0, 0)
 201
 202 /* The GCSE optimization will be disabled if it would require
 203    significantly more memory than this value.  */
 204 DEFPARAM(PARAM_MAX_GCSE_MEMORY,
 205          "max-gcse-memory",
 206          "The maximum amount of memory to be allocated by GCSE",
 207          50 * 1024 * 1024, 0, 0)
 208 /* The number of repetitions of copy/const prop and PRE to run.  */
 209 DEFPARAM(PARAM_MAX_GCSE_PASSES,
 210         "max-gcse-passes",
 211         "The maximum number of passes to make when doing GCSE",
 212         1, 1, 0)
 213 /* This is the threshold ratio when to perform partial redundancy
 214    elimination after reload. We perform partial redundancy elimination
 215    when the following holds:
 216    (Redundant load execution count)
 217    ------------------------------- >= GCSE_AFTER_RELOAD_PARTIAL_FRACTION
 218    (Added loads execution count)                                          */
 219 DEFPARAM(PARAM_GCSE_AFTER_RELOAD_PARTIAL_FRACTION,
 220         "gcse-after-reload-partial-fraction",
 221         "The threshold ratio for performing partial redundancy elimination after reload",
 222         3, 0, 0)
 223 /* This is the threshold ratio of the critical edges execution count compared to
 224    the redundant loads execution count that permits performing the load
 225    redundancy elimination in gcse after reload.  */
 226 DEFPARAM(PARAM_GCSE_AFTER_RELOAD_CRITICAL_FRACTION,
 227         "gcse-after-reload-critical-fraction",
 228         "The threshold ratio of critical edges execution count that permit performing redundancy elimination after reload",
 229         10, 0, 0)
 230 /* This parameter limits the number of insns in a loop that will be unrolled,
 231    and by how much the loop is unrolled.
 232
 233    This limit should be at most half of the peeling limits:  loop unroller
 234    decides to not unroll loops that iterate fewer than 2*number of allowed
 235    unrollings and thus we would have loops that are neither peeled or unrolled
 236    otherwise.  */
 237 DEFPARAM(PARAM_MAX_UNROLLED_INSNS,
 238          "max-unrolled-insns",
 239          "The maximum number of instructions to consider to unroll in a loop",
 240          200, 0, 0)
 241 /* This parameter limits how many times the loop is unrolled depending
 242    on number of insns really executed in each iteration.  */
 243 DEFPARAM(PARAM_MAX_AVERAGE_UNROLLED_INSNS,
 244          "max-average-unrolled-insns",
 245          "The maximum number of instructions to consider to unroll in a loop on average",
 246          80, 0, 0)
 247 /* The maximum number of unrollings of a single loop.  */
 248 DEFPARAM(PARAM_MAX_UNROLL_TIMES,
 249         "max-unroll-times",
 250         "The maximum number of unrollings of a single loop",
 251         8, 0, 0)
 252 /* The maximum number of insns of a peeled loop.  */
 253 DEFPARAM(PARAM_MAX_PEELED_INSNS,
 254         "max-peeled-insns",
 255         "The maximum number of insns of a peeled loop",
 256         400, 0, 0)
 257 /* The maximum number of peelings of a single loop.  */
 258 DEFPARAM(PARAM_MAX_PEEL_TIMES,
 259         "max-peel-times",
 260         "The maximum number of peelings of a single loop",
 261         16, 0, 0)
 262 /* The maximum number of insns of a peeled loop.  */
 263 DEFPARAM(PARAM_MAX_COMPLETELY_PEELED_INSNS,
 264         "max-completely-peeled-insns",
 265         "The maximum number of insns of a completely peeled loop",
 266         400, 0, 0)
 267 /* The maximum number of peelings of a single loop that is peeled completely.  */
 268 DEFPARAM(PARAM_MAX_COMPLETELY_PEEL_TIMES,
 269         "max-completely-peel-times",
 270         "The maximum number of peelings of a single loop that is peeled completely",
 271         16, 0, 0)
 272 /* The maximum number of insns of a peeled loop that rolls only once.  */
 273 DEFPARAM(PARAM_MAX_ONCE_PEELED_INSNS,
 274         "max-once-peeled-insns",
 275         "The maximum number of insns of a peeled loop that rolls only once",
 276         400, 0, 0)
 277
 278 /* The maximum number of insns of an unswitched loop.  */
 279 DEFPARAM(PARAM_MAX_UNSWITCH_INSNS,
 280         "max-unswitch-insns",
 281         "The maximum number of insns of an unswitched loop",
 282         50, 0, 0)
 283 /* The maximum level of recursion in unswitch_single_loop.  */
 284 DEFPARAM(PARAM_MAX_UNSWITCH_LEVEL,
 285         "max-unswitch-level",
 286         "The maximum number of unswitchings in a single loop",
 287         3, 0, 0)
 288
 289 /* The maximum number of iterations of a loop the brute force algorithm
 290    for analysis of # of iterations of the loop tries to evaluate.  */
 291 DEFPARAM(PARAM_MAX_ITERATIONS_TO_TRACK,
 292         "max-iterations-to-track",
 293         "Bound on the number of iterations the brute force # of iterations analysis algorithm evaluates",
 294         1000, 0, 0)
 295
 296 DEFPARAM(PARAM_MAX_SMS_LOOP_NUMBER,
 297          "max-sms-loop-number",
 298          "Maximum number of loops to perform swing modulo scheduling on (mainly for debugging)",
 299          -1, -1, -1)
 300
 301 /* This parameter is used to tune SMS MAX II calculations.  */
 302 DEFPARAM(PARAM_SMS_MAX_II_FACTOR,
 303          "sms-max-ii-factor",
 304          "A factor for tuning the upper bound that swing modulo scheduler uses for scheduling a loop",
 305          100, 0, 0)
 306 DEFPARAM(PARAM_SMS_DFA_HISTORY,
 307          "sms-dfa-history",
 308          "The number of cycles the swing modulo scheduler considers when checking conflicts using DFA",
 309          0, 0, 0)
 310 DEFPARAM(PARAM_SMS_LOOP_AVERAGE_COUNT_THRESHOLD,
 311          "sms-loop-average-count-threshold",
 312          "A threshold on the average loop count considered by the swing modulo scheduler",
 313          0, 0, 0)
 314
 315 DEFPARAM(HOT_BB_COUNT_FRACTION,
 316          "hot-bb-count-fraction",
 317          "Select fraction of the maximal count of repetitions of basic block in program given basic block needs to have to be considered hot",
 318          10000, 0, 0)
 319 DEFPARAM(HOT_BB_FREQUENCY_FRACTION,
 320          "hot-bb-frequency-fraction",
 321          "Select fraction of the maximal frequency of executions of basic block in function given basic block needs to have to be considered hot",
 322          1000, 0, 0)
 323
 324 /* For guessed profiles, the loops having unknown number of iterations
 325    are predicted to iterate relatively few (10) times at average.
 326    For functions containing one loop with large known number of iterations
 327    and other loops having unbounded loops we would end up predicting all
 328    the other loops cold that is not usually the case.  So we need to artificially
 329    flatten the profile.
 330
 331    We need to cut the maximal predicted iterations to large enough iterations
 332    so the loop appears important, but safely within HOT_BB_COUNT_FRACTION
 333    range.  */
 334
 335 DEFPARAM(PARAM_MAX_PREDICTED_ITERATIONS,
 336          "max-predicted-iterations",
 337          "The maximum number of loop iterations we predict statically",
 338          100, 0, 0)
 339 DEFPARAM(TRACER_DYNAMIC_COVERAGE_FEEDBACK,
 340          "tracer-dynamic-coverage-feedback",
 341          "The percentage of function, weighted by execution frequency, that must be covered by trace formation. Used when profile feedback is available",
 342          95, 0, 100)
 343 DEFPARAM(TRACER_DYNAMIC_COVERAGE,
 344          "tracer-dynamic-coverage",
 345          "The percentage of function, weighted by execution frequency, that must be covered by trace formation. Used when profile feedback is not available",
 346          75, 0, 100)
 347 DEFPARAM(TRACER_MAX_CODE_GROWTH,
 348          "tracer-max-code-growth",
 349          "Maximal code growth caused by tail duplication (in percent)",
 350          100, 0, 0)
 351 DEFPARAM(TRACER_MIN_BRANCH_RATIO,
 352          "tracer-min-branch-ratio",
 353          "Stop reverse growth if the reverse probability of best edge is less than this threshold (in percent)",
 354          10, 0, 100)
 355 DEFPARAM(TRACER_MIN_BRANCH_PROBABILITY_FEEDBACK,
 356          "tracer-min-branch-probability-feedback",
 357          "Stop forward growth if the probability of best edge is less than this threshold (in percent). Used when profile feedback is available",
 358          80, 0, 100)
 359 DEFPARAM(TRACER_MIN_BRANCH_PROBABILITY,
 360          "tracer-min-branch-probability",
 361          "Stop forward growth if the probability of best edge is less than this threshold (in percent). Used when profile feedback is not available",
 362          50, 0, 100)
 363
 364 /* The maximum number of incoming edges to consider for crossjumping.  */
 365 DEFPARAM(PARAM_MAX_CROSSJUMP_EDGES,
 366          "max-crossjump-edges",
 367          "The maximum number of incoming edges to consider for crossjumping",
 368          100, 0, 0)
 369
 370 /* The minimum number of matching instructions to consider for crossjumping.  */
 371 DEFPARAM(PARAM_MIN_CROSSJUMP_INSNS,
 372      "min-crossjump-insns",
 373      "The minimum number of matching instructions to consider for crossjumping",
 374      5, 0, 0)
 375
 376 /* The maximum number expansion factor when copying basic blocks.  */
 377 DEFPARAM(PARAM_MAX_GROW_COPY_BB_INSNS,
 378      "max-grow-copy-bb-insns",
 379      "The maximum expansion factor when copying basic blocks",
 380      8, 0, 0)
 381
 382 /* The maximum number of insns to duplicate when unfactoring computed gotos.  */
 383 DEFPARAM(PARAM_MAX_GOTO_DUPLICATION_INSNS,
 384      "max-goto-duplication-insns",
 385      "The maximum number of insns to duplicate when unfactoring computed gotos",
 386      8, 0, 0)
 387
 388 /* The maximum length of path considered in cse.  */
 389 DEFPARAM(PARAM_MAX_CSE_PATH_LENGTH,
 390          "max-cse-path-length",
 391          "The maximum length of path considered in cse",
 392          10, 0, 0)
 393 DEFPARAM(PARAM_MAX_CSE_INSNS,
 394          "max-flow-memory-locations",
 395          "The maximum instructions CSE process before flushing",
 396          1000, 0, 0)
 397
 398 /* The cost of expression in loop invariant motion that is considered
 399    expensive.  */
 400 DEFPARAM(PARAM_LIM_EXPENSIVE,
 401          "lim-expensive",
 402          "The minimum cost of an expensive expression in the loop invariant motion",
 403          20, 0, 0)
 404
 405 /* Bound on number of candidates for induction variables below that
 406    all candidates are considered for each use in induction variable
 407    optimizations.  */
 408
 409 DEFPARAM(PARAM_IV_CONSIDER_ALL_CANDIDATES_BOUND,
 410          "iv-consider-all-candidates-bound",
 411          "Bound on number of candidates below that all candidates are considered in iv optimizations",
 412          30, 0, 0)
 413
 414 /* The induction variable optimizations give up on loops that contain more
 415    induction variable uses.  */
 416
 417 DEFPARAM(PARAM_IV_MAX_CONSIDERED_USES,
 418          "iv-max-considered-uses",
 419          "Bound on number of iv uses in loop optimized in iv optimizations",
 420          250, 0, 0)
 421
 422 /* If there are at most this number of ivs in the set, try removing unnecessary
 423    ivs from the set always.  */
 424
 425 DEFPARAM(PARAM_IV_ALWAYS_PRUNE_CAND_SET_BOUND,
 426          "iv-always-prune-cand-set-bound",
 427          "If number of candidates in the set is smaller, we always try to remove unused ivs during its optimization",
 428          10, 0, 0)
 429
 430 DEFPARAM(PARAM_SCEV_MAX_EXPR_SIZE,
 431          "scev-max-expr-size",
 432          "Bound on size of expressions used in the scalar evolutions analyzer",
 433          20, 0, 0)
 434
 435 DEFPARAM(PARAM_VECT_MAX_VERSION_CHECKS,
 436          "vect-max-version-checks",
 437          "Bound on number of runtime checks inserted by the vectorizer's loop versioning",
 438          6, 0, 0)
 439
 440 /* The product of the next two is used to decide whether or not to
 441    use .GLOBAL_VAR.  See tree-dfa.c.  */
 442 DEFPARAM(PARAM_GLOBAL_VAR_THRESHOLD,
 443         "global-var-threshold",
 444         "Given N calls and V call-clobbered vars in a function.  Use .GLOBAL_VAR if NxV is larger than this limit",
 445         500000, 0, 0)
 446
 447 DEFPARAM(PARAM_MAX_CSELIB_MEMORY_LOCATIONS,
 448          "max-cselib-memory-locations",
 449          "The maximum memory locations recorded by cselib",
 450          500, 0, 0)
 451 DEFPARAM(PARAM_MAX_FLOW_MEMORY_LOCATIONS,
 452          "max-flow-memory-locations",
 453          "The maximum memory locations recorded by flow",
 454          100, 0, 0)
 455
 456 #ifdef ENABLE_GC_ALWAYS_COLLECT
 457 # define GGC_MIN_EXPAND_DEFAULT 0
 458 # define GGC_MIN_HEAPSIZE_DEFAULT 0
 459 #else
 460 # define GGC_MIN_EXPAND_DEFAULT 30
 461 # define GGC_MIN_HEAPSIZE_DEFAULT 4096
 462 #endif
 463
 464 DEFPARAM(GGC_MIN_EXPAND,
 465          "ggc-min-expand",
 466          "Minimum heap expansion to trigger garbage collection, as a percentage of the total size of the heap",
 467          GGC_MIN_EXPAND_DEFAULT, 0, 0)
 468
 469 DEFPARAM(GGC_MIN_HEAPSIZE,
 470          "ggc-min-heapsize",
 471          "Minimum heap size before we start collecting garbage, in kilobytes",
 472          GGC_MIN_HEAPSIZE_DEFAULT, 0, 0)
 473
 474 #undef GGC_MIN_EXPAND_DEFAULT
 475 #undef GGC_MIN_HEAPSIZE_DEFAULT
 476
 477 DEFPARAM(PARAM_MAX_RELOAD_SEARCH_INSNS,
 478          "max-reload-search-insns",
 479          "The maximum number of instructions to search backward when looking for equivalent reload",
 480          100, 0, 0)
 481
 482 DEFPARAM(PARAM_MAX_ALIASED_VOPS,
 483          "max-aliased-vops",
 484          "The maximum number of virtual operands allowed to represent aliases before triggering alias grouping",
 485          500, 0, 0)
 486
 487 DEFPARAM(PARAM_MAX_SCHED_REGION_BLOCKS,
 488          "max-sched-region-blocks",
 489          "The maximum number of blocks in a region to be considered for interblock scheduling",
 490          10, 0, 0)
 491
 492 DEFPARAM(PARAM_MAX_SCHED_REGION_INSNS,
 493          "max-sched-region-insns",
 494          "The maximum number of insns in a region to be considered for interblock scheduling",
 495          100, 0, 0)
 496
 497 DEFPARAM(PARAM_MIN_SPEC_PROB,
 498          "min-spec-prob",
 499          "The minimum probability of reaching a source block for interblock speculative scheduling",
 500          40, 0, 0)
 501
 502 DEFPARAM(PARAM_MAX_LAST_VALUE_RTL,
 503          "max-last-value-rtl",
 504          "The maximum number of RTL nodes that can be recorded as combiner's last value",
 505          10000, 0, 0)
 506
 507 /* INTEGER_CST nodes are shared for values [{-1,0} .. N) for
 508    {signed,unsigned} integral types.  This determines N.
 509    Experimentation shows 256 to be a good value.  */
 510 DEFPARAM (PARAM_INTEGER_SHARE_LIMIT,
 511           "integer-share-limit",
 512           "The upper bound for sharing integer constants",
 513           256, 2, 2)
 514
 515 /* Incremental SSA updates for virtual operands may be very slow if
 516    there is a large number of mappings to process.  In those cases, it
 517    is faster to rewrite the virtual symbols from scratch as if they
 518    had been recently introduced.  This heuristic cannot be applied to
 519    SSA mappings for real SSA names, only symbols kept in FUD chains.
 520
 521    PARAM_MIN_VIRTUAL_MAPPINGS specifies the minimum number of virtual
 522    mappings that should be registered to trigger the heuristic.
 523
 524    PARAM_VIRTUAL_MAPPINGS_TO_SYMS_RATIO specifies the ratio between
 525    mappings and symbols.  If the number of virtual mappings is
 526    PARAM_VIRTUAL_MAPPINGS_TO_SYMS_RATIO bigger than the number of
 527    virtual symbols to be updated, then the updater switches to a full
 528    update for those symbols.  */
 529 DEFPARAM (PARAM_MIN_VIRTUAL_MAPPINGS,
 530           "min-virtual-mappings",
 531           "Minimum number of virtual mappings to consider switching to full virtual renames",
 532           100, 0, 0)
 533
 534 DEFPARAM (PARAM_VIRTUAL_MAPPINGS_TO_SYMS_RATIO,
 535           "virtual-mappings-ratio",
 536           "Ratio between virtual mappings and virtual symbols to do full virtual renames",
 537           3, 0, 0)
 538
 539 DEFPARAM (PARAM_SSP_BUFFER_SIZE,
 540           "ssp-buffer-size",
 541           "The lower bound for a buffer to be considered for stack smashing protection",
 542           8, 1, 0)
 543
 544 /* When we thread through a block we have to make copies of the
 545    statements within the block.  Clearly for large blocks the code
 546    duplication is bad.
 547
 548    PARAM_MAX_JUMP_THREAD_DUPLICATION_STMTS specifies the maximum number
 549    of statements and PHI nodes allowed in a block which is going to
 550    be duplicated for thread jumping purposes.
 551
 552    Some simple analysis showed that more than 99% of the jump
 553    threading opportunities are for blocks with less than 15
 554    statements.  So we can get the benefits of jump threading
 555    without excessive code bloat for pathological cases with the
 556    throttle set at 15 statements.  */
 557 DEFPARAM (PARAM_MAX_JUMP_THREAD_DUPLICATION_STMTS,
 558           "max-jump-thread-duplication-stmts",
 559           "Maximum number of statements allowed in a block that needs to be duplicated when threading jumps",
 560           15, 0, 0)
 561
 562 /* This is the maximum number of fields a variable may have before the pointer analysis machinery
 563    will stop trying to treat it in a field-sensitive manner.
 564    There are programs out there with thousands of fields per structure, and handling them
 565    field-sensitively is not worth the cost.  */
 566 DEFPARAM (PARAM_MAX_FIELDS_FOR_FIELD_SENSITIVE,
 567           "max-fields-for-field-sensitive",
 568           "Maximum number of fields in a structure before pointer analysis treats the structure as a single variable",
 569           100, 0, 0)
 570 /*
 571 Local variables:
 572 mode:c
 573 End: */