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, 59 Temple Place - Suite 330, Boston, MA
  20 02111-1307, USA.
  21
  22 */
  23
  24 /* This file contains definitions for language-independent
  25    parameters.  The DEFPARAM macro takes 4 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    Be sure to add an entry to invoke.texi summarizing the parameter.  */
  37
  38 /* The maximum structure size at which the scalar replacement of
  39    aggregates (SRA) pass will perform block copies.  The default
  40    value, 0, implies that GCC will select the most appropriate size
  41    itself.  */
  42 DEFPARAM (PARAM_SRA_MAX_STRUCTURE_SIZE,
  43           "sra-max-structure-size",
  44           "The maximum structure size (in bytes) at which GCC will do block copies",
  45           0, 0, 0)
  46
  47 /* The ratio between instantiated fields and the complete structure
  48    size.  We say that if the ratio of the number of bytes in
  49    instantiated fields to the number of bytes in the complete
  50    structure exceeds this parameter, then block copies are not used.
  51    The default is 75%.  */
  52 DEFPARAM (PARAM_SRA_FIELD_STRUCTURE_RATIO,
  53           "sra-field-structure-ratio",
  54           "The threshold ratio between instantiated fields and the total structure size",
  55           75, 0, 100)
  56
  57 /* The single function inlining limit. This is the maximum size
  58    of a function counted in internal gcc instructions (not in
  59    real machine instructions) that is eligible for inlining
  60    by the tree inliner.
  61    The default value is 450.
  62    Only functions marked inline (or methods defined in the class
  63    definition for C++) are affected by this.
  64    There are more restrictions to inlining: If inlined functions
  65    call other functions, the already inlined instructions are
  66    counted and once the recursive inline limit (see
  67    "max-inline-insns" parameter) is exceeded, the acceptable size
  68    gets decreased.  */
  69 DEFPARAM (PARAM_MAX_INLINE_INSNS_SINGLE,
  70           "max-inline-insns-single",
  71           "The maximum number of instructions in a single function eligible for inlining",
  72           450, 0, 0)
  73
  74 /* The single function inlining limit for functions that are
  75    inlined by virtue of -finline-functions (-O3).
  76    This limit should be chosen to be below or equal to the limit
  77    that is applied to functions marked inlined (or defined in the
  78    class declaration in C++) given by the "max-inline-insns-single"
  79    parameter.
  80    The default value is 90.  */
  81 DEFPARAM (PARAM_MAX_INLINE_INSNS_AUTO,
  82           "max-inline-insns-auto",
  83           "The maximum number of instructions when automatically inlining",
  84           90, 0, 0)
  85
  86 DEFPARAM (PARAM_MAX_INLINE_INSNS_RECURSIVE,
  87           "max-inline-insns-recursive",
  88           "The maximum number of instructions inline function can grow to via recursive inlining",
  89           450, 0, 0)
  90
  91 DEFPARAM (PARAM_MAX_INLINE_INSNS_RECURSIVE_AUTO,
  92           "max-inline-insns-recursive-auto",
  93           "The maximum number of instructions non-inline function can grow to via recursive inlining",
  94           450, 0, 0)
  95
  96 DEFPARAM (PARAM_MAX_INLINE_RECURSIVE_DEPTH,
  97           "max-inline-recursive-depth",
  98           "The maximum depth of recursive inlining for inline functions",
  99           8, 0, 0)
 100
 101 DEFPARAM (PARAM_MAX_INLINE_RECURSIVE_DEPTH_AUTO,
 102           "max-inline-recursive-depth-auto",
 103           "The maximum depth of recursive inlining for non-inline functions",
 104           8, 0, 0)
 105
 106 /* Limit the number of expansions created by the variable expansion
 107    optimization to avoid register pressure.  */
 108 DEFPARAM (PARAM_MAX_VARIABLE_EXPANSIONS,
 109           "max-variable-expansions-in-unroller",
 110           "If -fvariable-expansion-in-unroller is used, the maximum number of \
 111            times that an individual variable will be expanded \
 112            during loop unrolling",
 113           1, 0, 0)
 114
 115 /* The maximum number of instructions to consider when looking for an
 116    instruction to fill a delay slot.  If more than this arbitrary
 117    number of instructions is searched, the time savings from filling
 118    the delay slot will be minimal so stop searching.  Increasing
 119    values mean more aggressive optimization, making the compile time
 120    increase with probably small improvement in executable run time.  */
 121 DEFPARAM (PARAM_MAX_DELAY_SLOT_INSN_SEARCH,
 122           "max-delay-slot-insn-search",
 123           "The maximum number of instructions to consider to fill a delay slot",
 124           100, 0, 0)
 125
 126 /* When trying to fill delay slots, the maximum number of instructions
 127    to consider when searching for a block with valid live register
 128    information.  Increasing this arbitrarily chosen value means more
 129    aggressive optimization, increasing the compile time.  This
 130    parameter should be removed when the delay slot code is rewritten
 131    to maintain the control-flow graph.  */
 132 DEFPARAM(PARAM_MAX_DELAY_SLOT_LIVE_SEARCH,
 133          "max-delay-slot-live-search",
 134          "The maximum number of instructions to consider to find accurate live register information",
 135          333, 0, 0)
 136
 137 /* This parameter limits the number of branch elements that the
 138    scheduler will track anti-dependencies through without resetting
 139    the tracking mechanism.  Large functions with few calls or barriers
 140    can generate lists containing many 1000's of dependencies.  Generally
 141    the compiler either uses all available memory, or runs for far too long.  */
 142 DEFPARAM(PARAM_MAX_PENDING_LIST_LENGTH,
 143          "max-pending-list-length",
 144          "The maximum length of scheduling's pending operations list",
 145          32, 0, 0)
 146
 147 DEFPARAM(PARAM_LARGE_FUNCTION_INSNS,
 148          "large-function-insns",
 149          "The size of function body to be considered large",
 150          2700, 0, 0)
 151 DEFPARAM(PARAM_LARGE_FUNCTION_GROWTH,
 152          "large-function-growth",
 153          "Maximal growth due to inlining of large function (in percent)",
 154          100, 0, 0)
 155 DEFPARAM(PARAM_INLINE_UNIT_GROWTH,
 156          "inline-unit-growth",
 157          "how much can given compilation unit grow because of the inlining (in percent)",
 158          50, 0, 0)
 159 DEFPARAM(PARAM_INLINE_CALL_COST,
 160          "inline-call-cost",
 161          "expense of call operation relative to ordinary arithmetic operations",
 162          16, 0, 0)
 163
 164 /* The GCSE optimization will be disabled if it would require
 165    significantly more memory than this value.  */
 166 DEFPARAM(PARAM_MAX_GCSE_MEMORY,
 167          "max-gcse-memory",
 168          "The maximum amount of memory to be allocated by GCSE",
 169          50 * 1024 * 1024, 0, 0)
 170 /* The number of repetitions of copy/const prop and PRE to run.  */
 171 DEFPARAM(PARAM_MAX_GCSE_PASSES,
 172         "max-gcse-passes",
 173         "The maximum number of passes to make when doing GCSE",
 174         1, 1, 0)
 175 /* This is the threshold ratio when to perform partial redundancy
 176    elimination after reload. We perform partial redundancy elimination
 177    when the following holds:
 178    (Redundant load execution count)
 179    ------------------------------- >= GCSE_AFTER_RELOAD_PARTIAL_FRACTION
 180    (Added loads execution count)                                          */
 181 DEFPARAM(PARAM_GCSE_AFTER_RELOAD_PARTIAL_FRACTION,
 182         "gcse-after-reload-partial-fraction",
 183         "The threshold ratio for performing partial redundancy elimination after reload.",
 184         3, 0, 0)
 185 /* This is the threshold ratio of the critical edges execution count compared to
 186    the redundant loads execution count that permits performing the load
 187    redundancy elimination in gcse after reload.  */
 188 DEFPARAM(PARAM_GCSE_AFTER_RELOAD_CRITICAL_FRACTION,
 189         "gcse-after-reload-critical-fraction",
 190         "The threshold ratio of critical edges execution count that permit performing redundancy elimination after reload.",
 191         10, 0, 0)
 192 /* This parameter limits the number of insns in a loop that will be unrolled,
 193    and by how much the loop is unrolled.
 194
 195    This limit should be at most half of the peeling limits:  loop unroller
 196    decides to not unroll loops that iterate fewer than 2*number of allowed
 197    unrollings and thus we would have loops that are neither peeled or unrolled
 198    otherwise.  */
 199 DEFPARAM(PARAM_MAX_UNROLLED_INSNS,
 200          "max-unrolled-insns",
 201          "The maximum number of instructions to consider to unroll in a loop",
 202          200, 0, 0)
 203 /* This parameter limits how many times the loop is unrolled depending
 204    on number of insns really executed in each iteration.  */
 205 DEFPARAM(PARAM_MAX_AVERAGE_UNROLLED_INSNS,
 206          "max-average-unrolled-insns",
 207          "The maximum number of instructions to consider to unroll in a loop on average",
 208          80, 0, 0)
 209 /* The maximum number of unrollings of a single loop.  */
 210 DEFPARAM(PARAM_MAX_UNROLL_TIMES,
 211         "max-unroll-times",
 212         "The maximum number of unrollings of a single loop",
 213         8, 0, 0)
 214 /* The maximum number of insns of a peeled loop.  */
 215 DEFPARAM(PARAM_MAX_PEELED_INSNS,
 216         "max-peeled-insns",
 217         "The maximum number of insns of a peeled loop",
 218         400, 0, 0)
 219 /* The maximum number of peelings of a single loop.  */
 220 DEFPARAM(PARAM_MAX_PEEL_TIMES,
 221         "max-peel-times",
 222         "The maximum number of peelings of a single loop",
 223         16, 0, 0)
 224 /* The maximum number of insns of a peeled loop.  */
 225 DEFPARAM(PARAM_MAX_COMPLETELY_PEELED_INSNS,
 226         "max-completely-peeled-insns",
 227         "The maximum number of insns of a completely peeled loop",
 228         400, 0, 0)
 229 /* The maximum number of peelings of a single loop that is peeled completely.  */
 230 DEFPARAM(PARAM_MAX_COMPLETELY_PEEL_TIMES,
 231         "max-completely-peel-times",
 232         "The maximum number of peelings of a single loop that is peeled completely",
 233         16, 0, 0)
 234 /* The maximum number of insns of a peeled loop that rolls only once.  */
 235 DEFPARAM(PARAM_MAX_ONCE_PEELED_INSNS,
 236         "max-once-peeled-insns",
 237         "The maximum number of insns of a peeled loop that rolls only once",
 238         400, 0, 0)
 239
 240 /* The maximum number of insns of an unswitched loop.  */
 241 DEFPARAM(PARAM_MAX_UNSWITCH_INSNS,
 242         "max-unswitch-insns",
 243         "The maximum number of insns of an unswitched loop",
 244         50, 0, 0)
 245 /* The maximum level of recursion in unswitch_single_loop.  */
 246 DEFPARAM(PARAM_MAX_UNSWITCH_LEVEL,
 247         "max-unswitch-level",
 248         "The maximum number of unswitchings in a single loop",
 249         3, 0, 0)
 250
 251 /* The maximum number of iterations of a loop the brute force algorithm
 252    for analysis of # of iterations of the loop tries to evaluate.  */
 253 DEFPARAM(PARAM_MAX_ITERATIONS_TO_TRACK,
 254         "max-iterations-to-track",
 255         "Bound on the number of iterations the brute force # of iterations analysis algorithm evaluates",
 256         1000, 0, 0)
 257
 258 DEFPARAM(PARAM_MAX_SMS_LOOP_NUMBER,
 259          "max-sms-loop-number",
 260          "Maximum number of loops to perform swing modulo scheduling on (mainly for debugging)",
 261          -1, -1, -1)
 262
 263 /* This parameter is used to tune SMS MAX II calculations.  */
 264 DEFPARAM(PARAM_SMS_MAX_II_FACTOR,
 265          "sms-max-ii-factor",
 266          "A factor for tuning the upper bound that swing modulo scheduler uses for scheduling a loop",
 267          100, 0, 0)
 268 DEFPARAM(PARAM_SMS_DFA_HISTORY,
 269          "sms-dfa-history",
 270          "The number of cycles the swing modulo scheduler considers when \
 271           checking conflicts using DFA",
 272          0, 0, 0)
 273 DEFPARAM(PARAM_SMS_LOOP_AVERAGE_COUNT_THRESHOLD,
 274          "sms-loop-average-count-threshold",
 275          "A threshold on the average loop count considered by the swing modulo scheduler",
 276          0, 0, 0)
 277
 278 DEFPARAM(HOT_BB_COUNT_FRACTION,
 279          "hot-bb-count-fraction",
 280          "Select fraction of the maximal count of repetitions of basic block in program given basic block needs to have to be considered hot",
 281          10000, 0, 0)
 282 DEFPARAM(HOT_BB_FREQUENCY_FRACTION,
 283          "hot-bb-frequency-fraction",
 284          "Select fraction of the maximal frequency of executions of basic block in function given basic block needs to have to be considered hot",
 285          1000, 0, 0)
 286 DEFPARAM(TRACER_DYNAMIC_COVERAGE_FEEDBACK,
 287          "tracer-dynamic-coverage-feedback",
 288          "The percentage of function, weighted by execution frequency, that must be covered by trace formation. Used when profile feedback is available",
 289          95, 0, 100)
 290 DEFPARAM(TRACER_DYNAMIC_COVERAGE,
 291          "tracer-dynamic-coverage",
 292          "The percentage of function, weighted by execution frequency, that must be covered by trace formation. Used when profile feedback is not available",
 293          75, 0, 100)
 294 DEFPARAM(TRACER_MAX_CODE_GROWTH,
 295          "tracer-max-code-growth",
 296          "Maximal code growth caused by tail duplication (in percent)",
 297          100, 0, 0)
 298 DEFPARAM(TRACER_MIN_BRANCH_RATIO,
 299          "tracer-min-branch-ratio",
 300          "Stop reverse growth if the reverse probability of best edge is less than this threshold (in percent)",
 301          10, 0, 100)
 302 DEFPARAM(TRACER_MIN_BRANCH_PROBABILITY_FEEDBACK,
 303          "tracer-min-branch-probability-feedback",
 304          "Stop forward growth if the probability of best edge is less than this threshold (in percent). Used when profile feedback is available",
 305          80, 0, 100)
 306 DEFPARAM(TRACER_MIN_BRANCH_PROBABILITY,
 307          "tracer-min-branch-probability",
 308          "Stop forward growth if the probability of best edge is less than this threshold (in percent). Used when profile feedback is not available",
 309          50, 0, 100)
 310
 311 /* The maximum number of incoming edges to consider for crossjumping.  */
 312 DEFPARAM(PARAM_MAX_CROSSJUMP_EDGES,
 313          "max-crossjump-edges",
 314          "The maximum number of incoming edges to consider for crossjumping",
 315          100, 0, 0)
 316
 317 /* The minimum number of matching instructions to consider for crossjumping.  */
 318 DEFPARAM(PARAM_MIN_CROSSJUMP_INSNS,
 319      "min-crossjump-insns",
 320      "The minimum number of matching instructions to consider for crossjumping",
 321      5, 0, 0)
 322
 323 /* The maximum number of insns to duplicate when unfactoring computed gotos.  */
 324 DEFPARAM(PARAM_MAX_GOTO_DUPLICATION_INSNS,
 325      "max-goto-duplication-insns",
 326      "The maximum number of insns to duplicate when unfactoring computed gotos",
 327      8, 0, 0)
 328
 329 /* The maximum length of path considered in cse.  */
 330 DEFPARAM(PARAM_MAX_CSE_PATH_LENGTH,
 331          "max-cse-path-length",
 332          "The maximum length of path considered in cse",
 333          10, 0, 0)
 334
 335 /* The cost of expression in loop invariant motion that is considered
 336    expensive.  */
 337 DEFPARAM(PARAM_LIM_EXPENSIVE,
 338          "lim-expensive",
 339          "The minimum cost of an expensive expression in the loop invariant motion",
 340          20, 0, 0)
 341
 342 /* Bound on number of candidates for induction variables below that
 343    all candidates are considered for each use in induction variable
 344    optimizations.  */
 345
 346 DEFPARAM(PARAM_IV_CONSIDER_ALL_CANDIDATES_BOUND,
 347          "iv-consider-all-candidates-bound",
 348          "Bound on number of candidates below that all candidates are considered in iv optimizations",
 349          30, 0, 0)
 350
 351 /* The induction variable optimizations give up on loops that contain more
 352    induction variable uses.  */
 353
 354 DEFPARAM(PARAM_IV_MAX_CONSIDERED_USES,
 355          "iv-max-considered-uses",
 356          "Bound on number of iv uses in loop optimized in iv optimizations",
 357          250, 0, 0)
 358
 359 /* If there are at most this number of ivs in the set, try removing unnecessary
 360    ivs from the set always.  */
 361
 362 DEFPARAM(PARAM_IV_ALWAYS_PRUNE_CAND_SET_BOUND,
 363          "iv-always-prune-cand-set-bound",
 364          "If number of candidates in the set is smaller, we always try to remove unused ivs during its optimization",
 365          10, 0, 0)
 366
 367 /* The product of the next two is used to decide whether or not to
 368    use .GLOBAL_VAR.  See tree-dfa.c.  */
 369 DEFPARAM(PARAM_GLOBAL_VAR_THRESHOLD,
 370         "global-var-threshold",
 371         "Given N calls and V call-clobbered vars in a function.  Use .GLOBAL_VAR if NxV is larger than this limit",
 372         500000, 0, 0)
 373
 374 DEFPARAM(PARAM_MAX_CSELIB_MEMORY_LOCATIONS,
 375          "max-cselib-memory-locations",
 376          "The maximum memory locations recorded by cselib",
 377          500, 0, 0)
 378
 379 #ifdef ENABLE_GC_ALWAYS_COLLECT
 380 # define GGC_MIN_EXPAND_DEFAULT 0
 381 # define GGC_MIN_HEAPSIZE_DEFAULT 0
 382 #else
 383 # define GGC_MIN_EXPAND_DEFAULT 30
 384 # define GGC_MIN_HEAPSIZE_DEFAULT 4096
 385 #endif
 386
 387 DEFPARAM(GGC_MIN_EXPAND,
 388          "ggc-min-expand",
 389          "Minimum heap expansion to trigger garbage collection, as a percentage of the total size of the heap",
 390          GGC_MIN_EXPAND_DEFAULT, 0, 0)
 391
 392 DEFPARAM(GGC_MIN_HEAPSIZE,
 393          "ggc-min-heapsize",
 394          "Minimum heap size before we start collecting garbage, in kilobytes",
 395          GGC_MIN_HEAPSIZE_DEFAULT, 0, 0)
 396
 397 #undef GGC_MIN_EXPAND_DEFAULT
 398 #undef GGC_MIN_HEAPSIZE_DEFAULT
 399
 400 DEFPARAM(PARAM_MAX_RELOAD_SEARCH_INSNS,
 401          "max-reload-search-insns",
 402          "The maximum number of instructions to search backward when looking for equivalent reload",
 403          100, 0, 0)
 404
 405 DEFPARAM(PARAM_MAX_ALIASED_VOPS,
 406          "max-aliased-vops",
 407          "The maximum number of virtual operands allowed to represent aliases before triggering alias grouping.",
 408          500, 0, 0)
 409
 410 DEFPARAM(PARAM_MAX_SCHED_REGION_BLOCKS,
 411          "max-sched-region-blocks",
 412          "The maximum number of blocks in a region to be considered for interblock scheduling",
 413          10, 0, 0)
 414
 415 DEFPARAM(PARAM_MAX_SCHED_REGION_INSNS,
 416          "max-sched-region-insns",
 417          "The maximum number of insns in a region to be considered for interblock scheduling",
 418          100, 0, 0)
 419
 420 DEFPARAM(PARAM_MAX_LAST_VALUE_RTL,
 421          "max-last-value-rtl",
 422          "The maximum number of RTL nodes that can be recorded as combiner's last value",
 423          10000, 0, 0)
 424
 425 /* INTEGER_CST nodes are shared for values [{-1,0} .. N) for
 426    {signed,unsigned} integral types.  This determines N.
 427    Experimentation shows 256 to be a good value.  */
 428 DEFPARAM (PARAM_INTEGER_SHARE_LIMIT,
 429           "integer-share-limit",
 430           "The upper bound for sharing integer constants",
 431           256, 2, 2)
 432
 433 /*
 434 Local variables:
 435 mode:c
 436 End: */