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) 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 DEFPARAM (PARAM_MIN_INLINE_RECURSIVE_PROBABILITY,
 120           "min-inline-recursive-probability",
 121           "Inline recursively only when the probability of call being executed exceeds the parameter",
 122           10, 0, 0)
 123
 124 /* Limit the number of expansions created by the variable expansion
 125    optimization to avoid register pressure.  */
 126 DEFPARAM (PARAM_MAX_VARIABLE_EXPANSIONS,
 127           "max-variable-expansions-in-unroller",
 128           "If -fvariable-expansion-in-unroller is used, the maximum number of \
 129            times that an individual variable will be expanded \
 130            during loop unrolling",
 131           1, 0, 0)
 132
 133 /* The maximum number of instructions to consider when looking for an
 134    instruction to fill a delay slot.  If more than this arbitrary
 135    number of instructions is searched, the time savings from filling
 136    the delay slot will be minimal so stop searching.  Increasing
 137    values mean more aggressive optimization, making the compile time
 138    increase with probably small improvement in executable run time.  */
 139 DEFPARAM (PARAM_MAX_DELAY_SLOT_INSN_SEARCH,
 140           "max-delay-slot-insn-search",
 141           "The maximum number of instructions to consider to fill a delay slot",
 142           100, 0, 0)
 143
 144 /* When trying to fill delay slots, the maximum number of instructions
 145    to consider when searching for a block with valid live register
 146    information.  Increasing this arbitrarily chosen value means more
 147    aggressive optimization, increasing the compile time.  This
 148    parameter should be removed when the delay slot code is rewritten
 149    to maintain the control-flow graph.  */
 150 DEFPARAM(PARAM_MAX_DELAY_SLOT_LIVE_SEARCH,
 151          "max-delay-slot-live-search",
 152          "The maximum number of instructions to consider to find accurate live register information",
 153          333, 0, 0)
 154
 155 /* This parameter limits the number of branch elements that the
 156    scheduler will track anti-dependencies through without resetting
 157    the tracking mechanism.  Large functions with few calls or barriers
 158    can generate lists containing many 1000's of dependencies.  Generally
 159    the compiler either uses all available memory, or runs for far too long.  */
 160 DEFPARAM(PARAM_MAX_PENDING_LIST_LENGTH,
 161          "max-pending-list-length",
 162          "The maximum length of scheduling's pending operations list",
 163          32, 0, 0)
 164
 165 DEFPARAM(PARAM_LARGE_FUNCTION_INSNS,
 166          "large-function-insns",
 167          "The size of function body to be considered large",
 168          2700, 0, 0)
 169 DEFPARAM(PARAM_LARGE_FUNCTION_GROWTH,
 170          "large-function-growth",
 171          "Maximal growth due to inlining of large function (in percent)",
 172          100, 0, 0)
 173 DEFPARAM(PARAM_INLINE_UNIT_GROWTH,
 174          "inline-unit-growth",
 175          "how much can given compilation unit grow because of the inlining (in percent)",
 176          50, 0, 0)
 177 DEFPARAM(PARAM_INLINE_CALL_COST,
 178          "inline-call-cost",
 179          "expense of call operation relative to ordinary arithmetic operations",
 180          16, 0, 0)
 181
 182 /* The GCSE optimization will be disabled if it would require
 183    significantly more memory than this value.  */
 184 DEFPARAM(PARAM_MAX_GCSE_MEMORY,
 185          "max-gcse-memory",
 186          "The maximum amount of memory to be allocated by GCSE",
 187          50 * 1024 * 1024, 0, 0)
 188 /* The number of repetitions of copy/const prop and PRE to run.  */
 189 DEFPARAM(PARAM_MAX_GCSE_PASSES,
 190         "max-gcse-passes",
 191         "The maximum number of passes to make when doing GCSE",
 192         1, 1, 0)
 193 /* This is the threshold ratio when to perform partial redundancy
 194    elimination after reload. We perform partial redundancy elimination
 195    when the following holds:
 196    (Redundant load execution count)
 197    ------------------------------- >= GCSE_AFTER_RELOAD_PARTIAL_FRACTION
 198    (Added loads execution count)                                          */
 199 DEFPARAM(PARAM_GCSE_AFTER_RELOAD_PARTIAL_FRACTION,
 200         "gcse-after-reload-partial-fraction",
 201         "The threshold ratio for performing partial redundancy elimination after reload",
 202         3, 0, 0)
 203 /* This is the threshold ratio of the critical edges execution count compared to
 204    the redundant loads execution count that permits performing the load
 205    redundancy elimination in gcse after reload.  */
 206 DEFPARAM(PARAM_GCSE_AFTER_RELOAD_CRITICAL_FRACTION,
 207         "gcse-after-reload-critical-fraction",
 208         "The threshold ratio of critical edges execution count that permit performing redundancy elimination after reload",
 209         10, 0, 0)
 210 /* This parameter limits the number of insns in a loop that will be unrolled,
 211    and by how much the loop is unrolled.
 212
 213    This limit should be at most half of the peeling limits:  loop unroller
 214    decides to not unroll loops that iterate fewer than 2*number of allowed
 215    unrollings and thus we would have loops that are neither peeled or unrolled
 216    otherwise.  */
 217 DEFPARAM(PARAM_MAX_UNROLLED_INSNS,
 218          "max-unrolled-insns",
 219          "The maximum number of instructions to consider to unroll in a loop",
 220          200, 0, 0)
 221 /* This parameter limits how many times the loop is unrolled depending
 222    on number of insns really executed in each iteration.  */
 223 DEFPARAM(PARAM_MAX_AVERAGE_UNROLLED_INSNS,
 224          "max-average-unrolled-insns",
 225          "The maximum number of instructions to consider to unroll in a loop on average",
 226          80, 0, 0)
 227 /* The maximum number of unrollings of a single loop.  */
 228 DEFPARAM(PARAM_MAX_UNROLL_TIMES,
 229         "max-unroll-times",
 230         "The maximum number of unrollings of a single loop",
 231         8, 0, 0)
 232 /* The maximum number of insns of a peeled loop.  */
 233 DEFPARAM(PARAM_MAX_PEELED_INSNS,
 234         "max-peeled-insns",
 235         "The maximum number of insns of a peeled loop",
 236         400, 0, 0)
 237 /* The maximum number of peelings of a single loop.  */
 238 DEFPARAM(PARAM_MAX_PEEL_TIMES,
 239         "max-peel-times",
 240         "The maximum number of peelings of a single loop",
 241         16, 0, 0)
 242 /* The maximum number of insns of a peeled loop.  */
 243 DEFPARAM(PARAM_MAX_COMPLETELY_PEELED_INSNS,
 244         "max-completely-peeled-insns",
 245         "The maximum number of insns of a completely peeled loop",
 246         400, 0, 0)
 247 /* The maximum number of peelings of a single loop that is peeled completely.  */
 248 DEFPARAM(PARAM_MAX_COMPLETELY_PEEL_TIMES,
 249         "max-completely-peel-times",
 250         "The maximum number of peelings of a single loop that is peeled completely",
 251         16, 0, 0)
 252 /* The maximum number of insns of a peeled loop that rolls only once.  */
 253 DEFPARAM(PARAM_MAX_ONCE_PEELED_INSNS,
 254         "max-once-peeled-insns",
 255         "The maximum number of insns of a peeled loop that rolls only once",
 256         400, 0, 0)
 257
 258 /* The maximum number of insns of an unswitched loop.  */
 259 DEFPARAM(PARAM_MAX_UNSWITCH_INSNS,
 260         "max-unswitch-insns",
 261         "The maximum number of insns of an unswitched loop",
 262         50, 0, 0)
 263 /* The maximum level of recursion in unswitch_single_loop.  */
 264 DEFPARAM(PARAM_MAX_UNSWITCH_LEVEL,
 265         "max-unswitch-level",
 266         "The maximum number of unswitchings in a single loop",
 267         3, 0, 0)
 268
 269 /* The maximum number of iterations of a loop the brute force algorithm
 270    for analysis of # of iterations of the loop tries to evaluate.  */
 271 DEFPARAM(PARAM_MAX_ITERATIONS_TO_TRACK,
 272         "max-iterations-to-track",
 273         "Bound on the number of iterations the brute force # of iterations analysis algorithm evaluates",
 274         1000, 0, 0)
 275
 276 DEFPARAM(PARAM_MAX_SMS_LOOP_NUMBER,
 277          "max-sms-loop-number",
 278          "Maximum number of loops to perform swing modulo scheduling on (mainly for debugging)",
 279          -1, -1, -1)
 280
 281 /* This parameter is used to tune SMS MAX II calculations.  */
 282 DEFPARAM(PARAM_SMS_MAX_II_FACTOR,
 283          "sms-max-ii-factor",
 284          "A factor for tuning the upper bound that swing modulo scheduler uses for scheduling a loop",
 285          100, 0, 0)
 286 DEFPARAM(PARAM_SMS_DFA_HISTORY,
 287          "sms-dfa-history",
 288          "The number of cycles the swing modulo scheduler considers when \
 289           checking conflicts using DFA",
 290          0, 0, 0)
 291 DEFPARAM(PARAM_SMS_LOOP_AVERAGE_COUNT_THRESHOLD,
 292          "sms-loop-average-count-threshold",
 293          "A threshold on the average loop count considered by the swing modulo scheduler",
 294          0, 0, 0)
 295
 296 DEFPARAM(HOT_BB_COUNT_FRACTION,
 297          "hot-bb-count-fraction",
 298          "Select fraction of the maximal count of repetitions of basic block in program given basic block needs to have to be considered hot",
 299          10000, 0, 0)
 300 DEFPARAM(HOT_BB_FREQUENCY_FRACTION,
 301          "hot-bb-frequency-fraction",
 302          "Select fraction of the maximal frequency of executions of basic block in function given basic block needs to have to be considered hot",
 303          1000, 0, 0)
 304 DEFPARAM(TRACER_DYNAMIC_COVERAGE_FEEDBACK,
 305          "tracer-dynamic-coverage-feedback",
 306          "The percentage of function, weighted by execution frequency, that must be covered by trace formation. Used when profile feedback is available",
 307          95, 0, 100)
 308 DEFPARAM(TRACER_DYNAMIC_COVERAGE,
 309          "tracer-dynamic-coverage",
 310          "The percentage of function, weighted by execution frequency, that must be covered by trace formation. Used when profile feedback is not available",
 311          75, 0, 100)
 312 DEFPARAM(TRACER_MAX_CODE_GROWTH,
 313          "tracer-max-code-growth",
 314          "Maximal code growth caused by tail duplication (in percent)",
 315          100, 0, 0)
 316 DEFPARAM(TRACER_MIN_BRANCH_RATIO,
 317          "tracer-min-branch-ratio",
 318          "Stop reverse growth if the reverse probability of best edge is less than this threshold (in percent)",
 319          10, 0, 100)
 320 DEFPARAM(TRACER_MIN_BRANCH_PROBABILITY_FEEDBACK,
 321          "tracer-min-branch-probability-feedback",
 322          "Stop forward growth if the probability of best edge is less than this threshold (in percent). Used when profile feedback is available",
 323          80, 0, 100)
 324 DEFPARAM(TRACER_MIN_BRANCH_PROBABILITY,
 325          "tracer-min-branch-probability",
 326          "Stop forward growth if the probability of best edge is less than this threshold (in percent). Used when profile feedback is not available",
 327          50, 0, 100)
 328
 329 /* The maximum number of incoming edges to consider for crossjumping.  */
 330 DEFPARAM(PARAM_MAX_CROSSJUMP_EDGES,
 331          "max-crossjump-edges",
 332          "The maximum number of incoming edges to consider for crossjumping",
 333          100, 0, 0)
 334
 335 /* The minimum number of matching instructions to consider for crossjumping.  */
 336 DEFPARAM(PARAM_MIN_CROSSJUMP_INSNS,
 337      "min-crossjump-insns",
 338      "The minimum number of matching instructions to consider for crossjumping",
 339      5, 0, 0)
 340
 341 /* The maximum number of insns to duplicate when unfactoring computed gotos.  */
 342 DEFPARAM(PARAM_MAX_GOTO_DUPLICATION_INSNS,
 343      "max-goto-duplication-insns",
 344      "The maximum number of insns to duplicate when unfactoring computed gotos",
 345      8, 0, 0)
 346
 347 /* The maximum length of path considered in cse.  */
 348 DEFPARAM(PARAM_MAX_CSE_PATH_LENGTH,
 349          "max-cse-path-length",
 350          "The maximum length of path considered in cse",
 351          10, 0, 0)
 352
 353 /* The cost of expression in loop invariant motion that is considered
 354    expensive.  */
 355 DEFPARAM(PARAM_LIM_EXPENSIVE,
 356          "lim-expensive",
 357          "The minimum cost of an expensive expression in the loop invariant motion",
 358          20, 0, 0)
 359
 360 /* Bound on number of candidates for induction variables below that
 361    all candidates are considered for each use in induction variable
 362    optimizations.  */
 363
 364 DEFPARAM(PARAM_IV_CONSIDER_ALL_CANDIDATES_BOUND,
 365          "iv-consider-all-candidates-bound",
 366          "Bound on number of candidates below that all candidates are considered in iv optimizations",
 367          30, 0, 0)
 368
 369 /* The induction variable optimizations give up on loops that contain more
 370    induction variable uses.  */
 371
 372 DEFPARAM(PARAM_IV_MAX_CONSIDERED_USES,
 373          "iv-max-considered-uses",
 374          "Bound on number of iv uses in loop optimized in iv optimizations",
 375          250, 0, 0)
 376
 377 /* If there are at most this number of ivs in the set, try removing unnecessary
 378    ivs from the set always.  */
 379
 380 DEFPARAM(PARAM_IV_ALWAYS_PRUNE_CAND_SET_BOUND,
 381          "iv-always-prune-cand-set-bound",
 382          "If number of candidates in the set is smaller, we always try to remove unused ivs during its optimization",
 383          10, 0, 0)
 384
 385 DEFPARAM(PARAM_SCEV_MAX_EXPR_SIZE,
 386          "scev-max-expr-size",
 387          "Bound on size of expressions used in the scalar evolutions analyzer",
 388          20, 0, 0)
 389
 390 /* The product of the next two is used to decide whether or not to
 391    use .GLOBAL_VAR.  See tree-dfa.c.  */
 392 DEFPARAM(PARAM_GLOBAL_VAR_THRESHOLD,
 393         "global-var-threshold",
 394         "Given N calls and V call-clobbered vars in a function.  Use .GLOBAL_VAR if NxV is larger than this limit",
 395         500000, 0, 0)
 396
 397 DEFPARAM(PARAM_MAX_CSELIB_MEMORY_LOCATIONS,
 398          "max-cselib-memory-locations",
 399          "The maximum memory locations recorded by cselib",
 400          500, 0, 0)
 401
 402 #ifdef ENABLE_GC_ALWAYS_COLLECT
 403 # define GGC_MIN_EXPAND_DEFAULT 0
 404 # define GGC_MIN_HEAPSIZE_DEFAULT 0
 405 #else
 406 # define GGC_MIN_EXPAND_DEFAULT 30
 407 # define GGC_MIN_HEAPSIZE_DEFAULT 4096
 408 #endif
 409
 410 DEFPARAM(GGC_MIN_EXPAND,
 411          "ggc-min-expand",
 412          "Minimum heap expansion to trigger garbage collection, as a percentage of the total size of the heap",
 413          GGC_MIN_EXPAND_DEFAULT, 0, 0)
 414
 415 DEFPARAM(GGC_MIN_HEAPSIZE,
 416          "ggc-min-heapsize",
 417          "Minimum heap size before we start collecting garbage, in kilobytes",
 418          GGC_MIN_HEAPSIZE_DEFAULT, 0, 0)
 419
 420 #undef GGC_MIN_EXPAND_DEFAULT
 421 #undef GGC_MIN_HEAPSIZE_DEFAULT
 422
 423 DEFPARAM(PARAM_MAX_RELOAD_SEARCH_INSNS,
 424          "max-reload-search-insns",
 425          "The maximum number of instructions to search backward when looking for equivalent reload",
 426          100, 0, 0)
 427
 428 DEFPARAM(PARAM_MAX_ALIASED_VOPS,
 429          "max-aliased-vops",
 430          "The maximum number of virtual operands allowed to represent aliases before triggering alias grouping",
 431          500, 0, 0)
 432
 433 DEFPARAM(PARAM_MAX_SCHED_REGION_BLOCKS,
 434          "max-sched-region-blocks",
 435          "The maximum number of blocks in a region to be considered for interblock scheduling",
 436          10, 0, 0)
 437
 438 DEFPARAM(PARAM_MAX_SCHED_REGION_INSNS,
 439          "max-sched-region-insns",
 440          "The maximum number of insns in a region to be considered for interblock scheduling",
 441          100, 0, 0)
 442
 443 DEFPARAM(PARAM_MAX_LAST_VALUE_RTL,
 444          "max-last-value-rtl",
 445          "The maximum number of RTL nodes that can be recorded as combiner's last value",
 446          10000, 0, 0)
 447
 448 /* INTEGER_CST nodes are shared for values [{-1,0} .. N) for
 449    {signed,unsigned} integral types.  This determines N.
 450    Experimentation shows 256 to be a good value.  */
 451 DEFPARAM (PARAM_INTEGER_SHARE_LIMIT,
 452           "integer-share-limit",
 453           "The upper bound for sharing integer constants",
 454           256, 2, 2)
 455
 456 /* Incremental SSA updates for virtual operands may be very slow if
 457    there is a large number of mappings to process.  In those cases, it
 458    is faster to rewrite the virtual symbols from scratch as if they
 459    had been recently introduced.  This heuristic cannot be applied to
 460    SSA mappings for real SSA names, only symbols kept in FUD chains.
 461
 462    PARAM_MIN_VIRTUAL_MAPPINGS specifies the minimum number of virtual
 463    mappings that should be registered to trigger the heuristic.
 464
 465    PARAM_VIRTUAL_MAPPINGS_TO_SYMS_RATIO specifies the ratio between
 466    mappings and symbols.  If the number of virtual mappings is
 467    PARAM_VIRTUAL_MAPPINGS_TO_SYMS_RATIO bigger than the number of
 468    virtual symbols to be updated, then the updater switches to a full
 469    update for those symbols.  */
 470 DEFPARAM (PARAM_MIN_VIRTUAL_MAPPINGS,
 471           "min-virtual-mappings",
 472           "Minimum number of virtual mappings to consider switching to full virtual renames",
 473           100, 0, 0)
 474
 475 DEFPARAM (PARAM_VIRTUAL_MAPPINGS_TO_SYMS_RATIO,
 476           "virtual-mappings-ratio",
 477           "Ratio between virtual mappings and virtual symbols to do full virtual renames",
 478           3, 0, 0)
 479
 480 DEFPARAM (PARAM_SSP_BUFFER_SIZE,
 481           "ssp-buffer-size",
 482           "The lower bound for a buffer to be considered for stack smashing protection",
 483           8, 1, 0)
 484
 485 /*
 486 Local variables:
 487 mode:c
 488 End: */