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