gcc/target.h

   1 /* Data structure definitions for a generic GCC target.
   2    Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
   3
   4 This program is free software; you can redistribute it and/or modify it
   5 under the terms of the GNU General Public License as published by the
   6 Free Software Foundation; either version 2, or (at your option) any
   7 later version.
   8
   9 This program is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 GNU General Public License for more details.
  13
  14 You should have received a copy of the GNU General Public License
  15 along with this program; if not, write to the Free Software
  16 Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17
  18  In other words, you are welcome to use, share and improve this program.
  19  You are forbidden to forbid anyone else to use, share and improve
  20  what you give them.   Help stamp out software-hoarding!  */
  21
  22 /* This file contains a data structure that describes a GCC target.
  23    At present it is incomplete, but in future it should grow to
  24    contain most or all target machine and target O/S specific
  25    information.
  26
  27    This structure has its initializer declared in target-def.h in the
  28    form of large macro TARGET_INITIALIZER that expands to many smaller
  29    macros.
  30
  31    The smaller macros each initialize one component of the structure,
  32    and each has a default.  Each target should have a file that
  33    includes target.h and target-def.h, and overrides any inappropriate
  34    defaults by undefining the relevant macro and defining a suitable
  35    replacement.  That file should then contain the definition of
  36    "targetm" like so:
  37
  38    struct gcc_target targetm = TARGET_INITIALIZER;
  39
  40    Doing things this way allows us to bring together everything that
  41    defines a GCC target.  By supplying a default that is appropriate
  42    to most targets, we can easily add new items without needing to
  43    edit dozens of target configuration files.  It should also allow us
  44    to gradually reduce the amount of conditional compilation that is
  45    scattered throughout GCC.  */
  46
  47 #ifndef GCC_TARGET_H
  48 #define GCC_TARGET_H
  49
  50 #include "tm.h"
  51 #include "insn-modes.h"
  52
  53 struct gcc_target
  54 {
  55   /* Functions that output assembler for the target.  */
  56   struct asm_out
  57   {
  58     /* Opening and closing parentheses for asm expression grouping.  */
  59     const char *open_paren, *close_paren;
  60
  61     /* Assembler instructions for creating various kinds of integer object.  */
  62     const char *byte_op;
  63     struct asm_int_op
  64     {
  65       const char *hi;
  66       const char *si;
  67       const char *di;
  68       const char *ti;
  69     } aligned_op, unaligned_op;
  70
  71     /* Try to output the assembler code for an integer object whose
  72        value is given by X.  SIZE is the size of the object in bytes and
  73        ALIGNED_P indicates whether it is aligned.  Return true if
  74        successful.  Only handles cases for which BYTE_OP, ALIGNED_OP
  75        and UNALIGNED_OP are NULL.  */
  76     bool (* integer) (rtx x, unsigned int size, int aligned_p);
  77
  78     /* Output code that will globalize a label.  */
  79     void (* globalize_label) (FILE *, const char *);
  80
  81     /* Output code that will emit a label for unwind info, if this
  82        target requires such labels.  Second argument is the decl the
  83        unwind info is associated with, third is a boolean: true if
  84        this is for exception handling, fourth is a boolean: true if
  85        this is only a placeholder for an omitted FDE.  */
  86     void (* unwind_label) (FILE *, tree, int, int);
  87
  88     /* Emit any directives required to unwind this instruction.  */
  89     void (* unwind_emit) (FILE *, rtx);
  90
  91     /* Output an internal label.  */
  92     void (* internal_label) (FILE *, const char *, unsigned long);
  93
  94     /* Emit an assembler directive to set visibility for the symbol
  95        associated with the tree decl.  */
  96     void (* visibility) (tree, int);
  97
  98     /* Output the assembler code for entry to a function.  */
  99     void (* function_prologue) (FILE *, HOST_WIDE_INT);
 100
 101     /* Output the assembler code for end of prologue.  */
 102     void (* function_end_prologue) (FILE *);
 103
 104     /* Output the assembler code for start of epilogue.  */
 105     void (* function_begin_epilogue) (FILE *);
 106
 107     /* Output the assembler code for function exit.  */
 108     void (* function_epilogue) (FILE *, HOST_WIDE_INT);
 109
 110     /* Tell assembler to change to section NAME with attributes FLAGS.
 111        If DECL is non-NULL, it is the VAR_DECL or FUNCTION_DECL with
 112        which this section is associated.  */
 113     void (* named_section) (const char *name, unsigned int flags, tree decl);
 114
 115     /* Switch to the section that holds the exception table.  */
 116     void (* exception_section) (void);
 117
 118     /* Switch to the section that holds the exception frames.  */
 119     void (* eh_frame_section) (void);
 120
 121     /* Select and switch to a section for EXP.  It may be a DECL or a
 122        constant.  RELOC is nonzero if runtime relocations must be applied;
 123        bit 1 will be set if the runtime relocations require non-local
 124        name resolution.  ALIGN is the required alignment of the data.  */
 125     void (* select_section) (tree, int, unsigned HOST_WIDE_INT);
 126
 127     /* Select and switch to a section for X with MODE.  ALIGN is
 128        the desired alignment of the data.  */
 129     void (* select_rtx_section) (enum machine_mode, rtx,
 130                                  unsigned HOST_WIDE_INT);
 131
 132     /* Select a unique section name for DECL.  RELOC is the same as
 133        for SELECT_SECTION.  */
 134     void (* unique_section) (tree, int);
 135
 136     /* Tell assembler to switch to the readonly data section associated
 137        with function DECL.  */
 138     void (* function_rodata_section) (tree);
 139
 140     /* Output a constructor for a symbol with a given priority.  */
 141     void (* constructor) (rtx, int);
 142
 143     /* Output a destructor for a symbol with a given priority.  */
 144     void (* destructor) (rtx, int);
 145
 146     /* Output the assembler code for a thunk function.  THUNK_DECL is the
 147        declaration for the thunk function itself, FUNCTION is the decl for
 148        the target function.  DELTA is an immediate constant offset to be
 149        added to THIS.  If VCALL_OFFSET is nonzero, the word at
 150        *(*this + vcall_offset) should be added to THIS.  */
 151     void (* output_mi_thunk) (FILE *file, tree thunk_decl,
 152                               HOST_WIDE_INT delta, HOST_WIDE_INT vcall_offset,
 153                               tree function_decl);
 154
 155     /* Determine whether output_mi_thunk would succeed.  */
 156     /* ??? Ideally, this hook would not exist, and success or failure
 157        would be returned from output_mi_thunk directly.  But there's
 158        too much undo-able setup involved in invoking output_mi_thunk.
 159        Could be fixed by making output_mi_thunk emit rtl instead of
 160        text to the output file.  */
 161     bool (* can_output_mi_thunk) (tree thunk_decl, HOST_WIDE_INT delta,
 162                                   HOST_WIDE_INT vcall_offset,
 163                                   tree function_decl);
 164
 165     /* Output any boilerplate text needed at the beginning of a
 166        translation unit.  */
 167     void (*file_start) (void);
 168
 169     /* Output any boilerplate text needed at the end of a
 170        translation unit.  */
 171     void (*file_end) (void);
 172
 173     /* Output an assembler pseudo-op to declare a library function name
 174        external.  */
 175     void (*external_libcall) (rtx);
 176
 177      /* Output an assembler directive to mark decl live. This instructs
 178         linker to not dead code strip this symbol.  */
 179     void (*mark_decl_preserved) (const char *);
 180
 181   } asm_out;
 182
 183   /* Functions relating to instruction scheduling.  */
 184   struct sched
 185   {
 186     /* Given the current cost, COST, of an insn, INSN, calculate and
 187        return a new cost based on its relationship to DEP_INSN through
 188        the dependence LINK.  The default is to make no adjustment.  */
 189     int (* adjust_cost) (rtx insn, rtx link, rtx def_insn, int cost);
 190
 191     /* Adjust the priority of an insn as you see fit.  Returns the new
 192        priority.  */
 193     int (* adjust_priority) (rtx, int);
 194
 195     /* Function which returns the maximum number of insns that can be
 196        scheduled in the same machine cycle.  This must be constant
 197        over an entire compilation.  The default is 1.  */
 198     int (* issue_rate) (void);
 199
 200     /* Calculate how much this insn affects how many more insns we
 201        can emit this cycle.  Default is they all cost the same.  */
 202     int (* variable_issue) (FILE *, int, rtx, int);
 203
 204     /* Initialize machine-dependent scheduling code.  */
 205     void (* md_init) (FILE *, int, int);
 206
 207     /* Finalize machine-dependent scheduling code.  */
 208     void (* md_finish) (FILE *, int);
 209
 210     /* Initialize machine-dependent function while scheduling code.  */
 211     void (* md_init_global) (FILE *, int, int);
 212
 213     /* Finalize machine-dependent function wide scheduling code.  */
 214     void (* md_finish_global) (FILE *, int);
 215
 216     /* Reorder insns in a machine-dependent fashion, in two different
 217        places.  Default does nothing.  */
 218     int (* reorder) (FILE *, int, rtx *, int *, int);
 219     int (* reorder2) (FILE *, int, rtx *, int *, int);
 220
 221     /* The following member value is a pointer to a function called
 222        after evaluation forward dependencies of insns in chain given
 223        by two parameter values (head and tail correspondingly).  */
 224     void (* dependencies_evaluation_hook) (rtx, rtx);
 225
 226     /* The values of the following four members are pointers to
 227        functions used to simplify the automaton descriptions.
 228        dfa_pre_cycle_insn and dfa_post_cycle_insn give functions
 229        returning insns which are used to change the pipeline hazard
 230        recognizer state when the new simulated processor cycle
 231        correspondingly starts and finishes.  The function defined by
 232        init_dfa_pre_cycle_insn and init_dfa_post_cycle_insn are used
 233        to initialize the corresponding insns.  The default values of
 234        the members result in not changing the automaton state when
 235        the new simulated processor cycle correspondingly starts and
 236        finishes.  */
 237     void (* init_dfa_pre_cycle_insn) (void);
 238     rtx (* dfa_pre_cycle_insn) (void);
 239     void (* init_dfa_post_cycle_insn) (void);
 240     rtx (* dfa_post_cycle_insn) (void);
 241
 242     /* The following member value is a pointer to a function returning value
 243        which defines how many insns in queue `ready' will we try for
 244        multi-pass scheduling.  If the member value is nonzero and the
 245        function returns positive value, the DFA based scheduler will make
 246        multi-pass scheduling for the first cycle.  In other words, we will
 247        try to choose ready insn which permits to start maximum number of
 248        insns on the same cycle.  */
 249     int (* first_cycle_multipass_dfa_lookahead) (void);
 250
 251     /* The following member value is pointer to a function controlling
 252        what insns from the ready insn queue will be considered for the
 253        multipass insn scheduling.  If the hook returns zero for insn
 254        passed as the parameter, the insn will be not chosen to be
 255        issued.  */
 256     int (* first_cycle_multipass_dfa_lookahead_guard) (rtx);
 257
 258     /* The following member value is pointer to a function called by
 259        the insn scheduler before issuing insn passed as the third
 260        parameter on given cycle.  If the hook returns nonzero, the
 261        insn is not issued on given processors cycle.  Instead of that,
 262        the processor cycle is advanced.  If the value passed through
 263        the last parameter is zero, the insn ready queue is not sorted
 264        on the new cycle start as usually.  The first parameter passes
 265        file for debugging output.  The second one passes the scheduler
 266        verbose level of the debugging output.  The forth and the fifth
 267        parameter values are correspondingly processor cycle on which
 268        the previous insn has been issued and the current processor
 269        cycle.  */
 270     int (* dfa_new_cycle) (FILE *, int, rtx, int, int, int *);
 271
 272     /* The following member value is a pointer to a function called
 273        by the insn scheduler.  It should return true if there exists a
 274        dependence which is considered costly by the target, between
 275        the insn passed as the first parameter, and the insn passed as
 276        the second parameter.  The third parameter is the INSN_DEPEND
 277        link that represents the dependence between the two insns.  The
 278        fourth argument is the cost of the dependence as estimated by
 279        the scheduler.  The last argument is the distance in cycles
 280        between the already scheduled insn (first parameter) and the
 281        the second insn (second parameter).  */
 282     bool (* is_costly_dependence) (rtx, rtx, rtx, int, int);
 283   } sched;
 284
 285   /* Functions relating to vectorization.  */
 286   struct vectorize
 287   {
 288     /* The following member value is a pointer to a function called
 289        by the vectorizer, and return the decl of the target builtin
 290        function.  */
 291     tree (* builtin_mask_for_load) (void);
 292   } vectorize;
 293
 294   /* Return machine mode for filter value.  */
 295   enum machine_mode (* eh_return_filter_mode) (void);
 296
 297   /* Given two decls, merge their attributes and return the result.  */
 298   tree (* merge_decl_attributes) (tree, tree);
 299
 300   /* Given two types, merge their attributes and return the result.  */
 301   tree (* merge_type_attributes) (tree, tree);
 302
 303   /* Table of machine attributes and functions to handle them.
 304      Ignored if NULL.  */
 305   const struct attribute_spec *attribute_table;
 306
 307   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 308      one if they are compatible and two if they are nearly compatible
 309      (which causes a warning to be generated).  */
 310   int (* comp_type_attributes) (tree type1, tree type2);
 311
 312   /* Assign default attributes to the newly defined TYPE.  */
 313   void (* set_default_type_attributes) (tree type);
 314
 315   /* Insert attributes on the newly created DECL.  */
 316   void (* insert_attributes) (tree decl, tree *attributes);
 317
 318   /* Return true if FNDECL (which has at least one machine attribute)
 319      can be inlined despite its machine attributes, false otherwise.  */
 320   bool (* function_attribute_inlinable_p) (tree fndecl);
 321
 322   /* Return true if bitfields in RECORD_TYPE should follow the
 323      Microsoft Visual C++ bitfield layout rules.  */
 324   bool (* ms_bitfield_layout_p) (tree record_type);
 325
 326   /* Return true if anonymous bitfields affect structure alignment.  */
 327   bool (* align_anon_bitfield) (void);
 328
 329   /* Set up target-specific built-in functions.  */
 330   void (* init_builtins) (void);
 331
 332   /* Expand a target-specific builtin.  */
 333   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 334                           enum machine_mode mode, int ignore);
 335
 336   /* Fold a target-specific builtin.  */
 337   tree (* fold_builtin) (tree exp, bool ignore);
 338
 339   /* For a vendor-specific fundamental TYPE, return a pointer to
 340      a statically-allocated string containing the C++ mangling for
 341      TYPE.  In all other cases, return NULL.  */
 342   const char * (* mangle_fundamental_type) (tree type);
 343
 344   /* Make any adjustments to libfunc names needed for this target.  */
 345   void (* init_libfuncs) (void);
 346
 347   /* Given a decl, a section name, and whether the decl initializer
 348      has relocs, choose attributes for the section.  */
 349   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 350   unsigned int (* section_type_flags) (tree, const char *, int);
 351
 352   /* True if new jumps cannot be created, to replace existing ones or
 353      not, at the current point in the compilation.  */
 354   bool (* cannot_modify_jumps_p) (void);
 355
 356   /* Return a register class for which branch target register
 357      optimizations should be applied.  */
 358   int (* branch_target_register_class) (void);
 359
 360   /* Return true if branch target register optimizations should include
 361      callee-saved registers that are not already live during the current
 362      function.  AFTER_PE_GEN is true if prologues and epilogues have
 363      already been generated.  */
 364   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 365
 366   /* True if the constant X cannot be placed in the constant pool.  */
 367   bool (* cannot_force_const_mem) (rtx);
 368
 369   /* True if the insn X cannot be duplicated.  */
 370   bool (* cannot_copy_insn_p) (rtx);
 371
 372   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 373   rtx (* delegitimize_address) (rtx);
 374
 375   /* True if it is OK to do sibling call optimization for the specified
 376      call expression EXP.  DECL will be the called function, or NULL if
 377      this is an indirect call.  */
 378   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 379
 380   /* True if EXP should be placed in a "small data" section.  */
 381   bool (* in_small_data_p) (tree);
 382
 383   /* True if EXP names an object for which name resolution must resolve
 384      to the current module.  */
 385   bool (* binds_local_p) (tree);
 386
 387   /* Do something target-specific to record properties of the DECL into
 388      the associated SYMBOL_REF.  */
 389   void (* encode_section_info) (tree, rtx, int);
 390
 391   /* Undo the effects of encode_section_info on the symbol string.  */
 392   const char * (* strip_name_encoding) (const char *);
 393
 394   /* If shift optabs for MODE are known to always truncate the shift count,
 395      return the mask that they apply.  Return 0 otherwise.  */
 396   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
 397
 398   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 399   bool (* valid_pointer_mode) (enum machine_mode mode);
 400
 401   /* True if MODE is valid for the target.  By "valid", we mean able to
 402      be manipulated in non-trivial ways.  In particular, this means all
 403      the arithmetic is supported.  */
 404   bool (* scalar_mode_supported_p) (enum machine_mode mode);
 405
 406   /* Similarly for vector modes.  "Supported" here is less strict.  At
 407      least some operations are supported; need to check optabs or builtins
 408      for further details.  */
 409   bool (* vector_mode_supported_p) (enum machine_mode mode);
 410
 411   /* True if a vector is opaque.  */
 412   bool (* vector_opaque_p) (tree);
 413
 414   /* Compute a (partial) cost for rtx X.  Return true if the complete
 415      cost has been computed, and false if subexpressions should be
 416      scanned.  In either case, *TOTAL contains the cost result.  */
 417   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 418      not necessarily defined at this point.  */
 419   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 420
 421   /* Compute the cost of X, used as an address.  Never called with
 422      invalid addresses.  */
 423   int (* address_cost) (rtx x);
 424
 425   /* Given a register, this hook should return a parallel of registers
 426      to represent where to find the register pieces.  Define this hook
 427      if the register and its mode are represented in Dwarf in
 428      non-contiguous locations, or if the register should be
 429      represented in more than one register in Dwarf.  Otherwise, this
 430      hook should return NULL_RTX.  */
 431   rtx (* dwarf_register_span) (rtx);
 432
 433   /* Fetch the fixed register(s) which hold condition codes, for
 434      targets where it makes sense to look for duplicate assignments to
 435      the condition codes.  This should return true if there is such a
 436      register, false otherwise.  The arguments should be set to the
 437      fixed register numbers.  Up to two condition code registers are
 438      supported.  If there is only one for this target, the int pointed
 439      at by the second argument should be set to -1.  */
 440   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 441
 442   /* If two condition code modes are compatible, return a condition
 443      code mode which is compatible with both, such that a comparison
 444      done in the returned mode will work for both of the original
 445      modes.  If the condition code modes are not compatible, return
 446      VOIDmode.  */
 447   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 448                                              enum machine_mode);
 449
 450   /* Do machine-dependent code transformations.  Called just before
 451      delayed-branch scheduling.  */
 452   void (* machine_dependent_reorg) (void);
 453
 454   /* Create the __builtin_va_list type.  */
 455   tree (* build_builtin_va_list) (void);
 456
 457   /* Gimplifies a VA_ARG_EXPR.  */
 458   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 459                                  tree *post_p);
 460
 461   /* Validity-checking routines for PCH files, target-specific.
 462      get_pch_validity returns a pointer to the data to be stored,
 463      and stores the size in its argument.  pch_valid_p gets the same
 464      information back and returns NULL if the PCH is valid,
 465      or an error message if not.
 466   */
 467   void * (* get_pch_validity) (size_t *);
 468   const char * (* pch_valid_p) (const void *, size_t);
 469
 470   /* True if the compiler should give an enum type only as many
 471      bytes as it takes to represent the range of possible values of
 472      that type.  */
 473   bool (* default_short_enums) (void);
 474
 475   /* This target hook returns an rtx that is used to store the address
 476      of the current frame into the built-in setjmp buffer.  */
 477   rtx (* builtin_setjmp_frame_value) (void);
 478
 479   /* This target hook should add STRING_CST trees for any hard regs
 480      the port wishes to automatically clobber for all asms.  */
 481   tree (* md_asm_clobbers) (tree);
 482
 483   /* This target hook allows the backend to specify a calling convention
 484      in the debug information.  This function actually returns an
 485      enum dwarf_calling_convention, but because of forward declarations
 486      and not wanting to include dwarf2.h everywhere target.h is included
 487      the function is being declared as an int.  */
 488   int (* dwarf_calling_convention) (tree);
 489
 490   /* This target hook allows the backend to emit frame-related insns that
 491      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
 492      engine will invoke it on insns of the form
 493        (set (reg) (unspec [...] UNSPEC_INDEX))
 494      and
 495        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
 496      to let the backend emit the call frame instructions.  */
 497   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
 498
 499   /* Functions relating to calls - argument passing, returns, etc.  */
 500   struct calls {
 501     bool (*promote_function_args) (tree fntype);
 502     bool (*promote_function_return) (tree fntype);
 503     bool (*promote_prototypes) (tree fntype);
 504     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 505     bool (*return_in_memory) (tree type, tree fndecl);
 506     bool (*return_in_msb) (tree type);
 507
 508     /* Return true if a parameter must be passed by reference.  TYPE may
 509        be null if this is a libcall.  CA may be null if this query is
 510        from __builtin_va_arg.  */
 511     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 512                                tree type, bool named_arg);
 513
 514     rtx (*expand_builtin_saveregs) (void);
 515     /* Returns pretend_argument_size.  */
 516     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 517                                     tree type, int *pretend_arg_size,
 518                                     int second_time);
 519     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 520     /* Returns true if we should use
 521        targetm.calls.setup_incoming_varargs() and/or
 522        targetm.calls.strict_argument_naming().  */
 523     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 524
 525     /* Given a complex type T, return true if a parameter of type T
 526        should be passed as two scalars.  */
 527     bool (* split_complex_arg) (tree type);
 528
 529     /* Return true if type T, mode MODE, may not be passed in registers,
 530        but must be passed on the stack.  */
 531     /* ??? This predicate should be applied strictly after pass-by-reference.
 532        Need audit to verify that this is the case.  */
 533     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 534
 535     /* Return true if type TYPE, mode MODE, which is passed by reference,
 536        should have the object copy generated by the callee rather than
 537        the caller.  It is never called for TYPE requiring constructors.  */
 538     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 539                             tree type, bool named);
 540
 541     /* Return zero for arguments passed entirely on the stack or entirely
 542        in registers.  If passed in both, return the number of bytes passed
 543        in registers; the balance is therefore passed on the stack.  */
 544     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 545                                tree type, bool named);
 546   } calls;
 547
 548   /* Functions specific to the C++ frontend.  */
 549   struct cxx {
 550     /* Return the integer type used for guard variables.  */
 551     tree (*guard_type) (void);
 552     /* Return true if only the low bit of the guard should be tested.  */
 553     bool (*guard_mask_bit) (void);
 554     /* Returns the size of the array cookie for an array of type.  */
 555     tree (*get_cookie_size) (tree);
 556     /* Returns true if the element size should be stored in the
 557        array cookie.  */
 558     bool (*cookie_has_size) (void);
 559     /* Allows backends to perform additional processing when
 560        deciding if a class should be exported or imported.  */
 561     int (*import_export_class) (tree, int);
 562     /* Returns true if constructors and destructors return "this".  */
 563     bool (*cdtor_returns_this) (void);
 564     /* Returns true if the key method for a class can be an inline
 565        function, so long as it is not declared inline in the class
 566        itself.  Returning true is the behavior required by the Itanium
 567        C++ ABI.  */
 568     bool (*key_method_may_be_inline) (void);
 569     /* Returns true if all class data (virtual tables, type info,
 570        etc.) should be exported from the current DLL, even when the
 571        associated class is not exported.  */
 572     bool (*export_class_data) (void);
 573   } cxx;
 574
 575   /* Leave the boolean fields at the end.  */
 576
 577   /* True if arbitrary sections are supported.  */
 578   bool have_named_sections;
 579
 580   /* True if "native" constructors and destructors are supported,
 581      false if we're using collect2 for the job.  */
 582   bool have_ctors_dtors;
 583
 584   /* True if thread-local storage is supported.  */
 585   bool have_tls;
 586
 587   /* True if a small readonly data section is supported.  */
 588   bool have_srodata_section;
 589
 590   /* True if EH frame info sections should be zero-terminated.  */
 591   bool terminate_dw2_eh_frame_info;
 592
 593   /* True if #NO_APP should be emitted at the beginning of
 594      assembly output.  */
 595   bool file_start_app_off;
 596
 597   /* True if output_file_directive should be called for main_input_filename
 598      at the beginning of assembly output.  */
 599   bool file_start_file_directive;
 600
 601   /* True if #pragma redefine_extname is to be supported.  */
 602   bool handle_pragma_redefine_extname;
 603
 604   /* True if #pragma extern_prefix is to be supported.  */
 605   bool handle_pragma_extern_prefix;
 606
 607   /* True if the target is allowed to reorder memory accesses unless
 608      synchronization is explicitly requested.  */
 609   bool relaxed_ordering;
 610
 611   /* Leave the boolean fields at the end.  */
 612 };
 613
 614 extern struct gcc_target targetm;
 615
 616 #endif /* GCC_TARGET_H */