gcc/target.h

   1 /* Data structure definitions for a generic GCC target.
   2    Copyright (C) 2001, 2002, 2003, 2004, 2005 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 stdarg_info;
  54
  55 struct gcc_target
  56 {
  57   /* Functions that output assembler for the target.  */
  58   struct asm_out
  59   {
  60     /* Opening and closing parentheses for asm expression grouping.  */
  61     const char *open_paren, *close_paren;
  62
  63     /* Assembler instructions for creating various kinds of integer object.  */
  64     const char *byte_op;
  65     struct asm_int_op
  66     {
  67       const char *hi;
  68       const char *si;
  69       const char *di;
  70       const char *ti;
  71     } aligned_op, unaligned_op;
  72
  73     /* Try to output the assembler code for an integer object whose
  74        value is given by X.  SIZE is the size of the object in bytes and
  75        ALIGNED_P indicates whether it is aligned.  Return true if
  76        successful.  Only handles cases for which BYTE_OP, ALIGNED_OP
  77        and UNALIGNED_OP are NULL.  */
  78     bool (* integer) (rtx x, unsigned int size, int aligned_p);
  79
  80     /* Output code that will globalize a label.  */
  81     void (* globalize_label) (FILE *, const char *);
  82
  83     /* Output code that will emit a label for unwind info, if this
  84        target requires such labels.  Second argument is the decl the
  85        unwind info is associated with, third is a boolean: true if
  86        this is for exception handling, fourth is a boolean: true if
  87        this is only a placeholder for an omitted FDE.  */
  88     void (* unwind_label) (FILE *, tree, int, int);
  89
  90     /* Emit any directives required to unwind this instruction.  */
  91     void (* unwind_emit) (FILE *, rtx);
  92
  93     /* Output an internal label.  */
  94     void (* internal_label) (FILE *, const char *, unsigned long);
  95
  96     /* Emit an assembler directive to set visibility for the symbol
  97        associated with the tree decl.  */
  98     void (* visibility) (tree, int);
  99
 100     /* Output the assembler code for entry to a function.  */
 101     void (* function_prologue) (FILE *, HOST_WIDE_INT);
 102
 103     /* Output the assembler code for end of prologue.  */
 104     void (* function_end_prologue) (FILE *);
 105
 106     /* Output the assembler code for start of epilogue.  */
 107     void (* function_begin_epilogue) (FILE *);
 108
 109     /* Output the assembler code for function exit.  */
 110     void (* function_epilogue) (FILE *, HOST_WIDE_INT);
 111
 112     /* Tell assembler to change to section NAME with attributes FLAGS.
 113        If DECL is non-NULL, it is the VAR_DECL or FUNCTION_DECL with
 114        which this section is associated.  */
 115     void (* named_section) (const char *name, unsigned int flags, tree decl);
 116
 117     /* Switch to the section that holds the exception table.  */
 118     void (* exception_section) (void);
 119
 120     /* Switch to the section that holds the exception frames.  */
 121     void (* eh_frame_section) (void);
 122
 123     /* Select and switch to a section for EXP.  It may be a DECL or a
 124        constant.  RELOC is nonzero if runtime relocations must be applied;
 125        bit 1 will be set if the runtime relocations require non-local
 126        name resolution.  ALIGN is the required alignment of the data.  */
 127     void (* select_section) (tree, int, unsigned HOST_WIDE_INT);
 128
 129     /* Select and switch to a section for X with MODE.  ALIGN is
 130        the desired alignment of the data.  */
 131     void (* select_rtx_section) (enum machine_mode, rtx,
 132                                  unsigned HOST_WIDE_INT);
 133
 134     /* Select a unique section name for DECL.  RELOC is the same as
 135        for SELECT_SECTION.  */
 136     void (* unique_section) (tree, int);
 137
 138     /* Tell assembler to switch to the readonly data section associated
 139        with function DECL.  */
 140     void (* function_rodata_section) (tree);
 141
 142     /* Output a constructor for a symbol with a given priority.  */
 143     void (* constructor) (rtx, int);
 144
 145     /* Output a destructor for a symbol with a given priority.  */
 146     void (* destructor) (rtx, int);
 147
 148     /* Output the assembler code for a thunk function.  THUNK_DECL is the
 149        declaration for the thunk function itself, FUNCTION is the decl for
 150        the target function.  DELTA is an immediate constant offset to be
 151        added to THIS.  If VCALL_OFFSET is nonzero, the word at
 152        *(*this + vcall_offset) should be added to THIS.  */
 153     void (* output_mi_thunk) (FILE *file, tree thunk_decl,
 154                               HOST_WIDE_INT delta, HOST_WIDE_INT vcall_offset,
 155                               tree function_decl);
 156
 157     /* Determine whether output_mi_thunk would succeed.  */
 158     /* ??? Ideally, this hook would not exist, and success or failure
 159        would be returned from output_mi_thunk directly.  But there's
 160        too much undo-able setup involved in invoking output_mi_thunk.
 161        Could be fixed by making output_mi_thunk emit rtl instead of
 162        text to the output file.  */
 163     bool (* can_output_mi_thunk) (tree thunk_decl, HOST_WIDE_INT delta,
 164                                   HOST_WIDE_INT vcall_offset,
 165                                   tree function_decl);
 166
 167     /* Output any boilerplate text needed at the beginning of a
 168        translation unit.  */
 169     void (*file_start) (void);
 170
 171     /* Output any boilerplate text needed at the end of a
 172        translation unit.  */
 173     void (*file_end) (void);
 174
 175     /* Output an assembler pseudo-op to declare a library function name
 176        external.  */
 177     void (*external_libcall) (rtx);
 178
 179      /* Output an assembler directive to mark decl live. This instructs
 180         linker to not dead code strip this symbol.  */
 181     void (*mark_decl_preserved) (const char *);
 182
 183   } asm_out;
 184
 185   /* Functions relating to instruction scheduling.  */
 186   struct sched
 187   {
 188     /* Given the current cost, COST, of an insn, INSN, calculate and
 189        return a new cost based on its relationship to DEP_INSN through
 190        the dependence LINK.  The default is to make no adjustment.  */
 191     int (* adjust_cost) (rtx insn, rtx link, rtx def_insn, int cost);
 192
 193     /* Adjust the priority of an insn as you see fit.  Returns the new
 194        priority.  */
 195     int (* adjust_priority) (rtx, int);
 196
 197     /* Function which returns the maximum number of insns that can be
 198        scheduled in the same machine cycle.  This must be constant
 199        over an entire compilation.  The default is 1.  */
 200     int (* issue_rate) (void);
 201
 202     /* Calculate how much this insn affects how many more insns we
 203        can emit this cycle.  Default is they all cost the same.  */
 204     int (* variable_issue) (FILE *, int, rtx, int);
 205
 206     /* Initialize machine-dependent scheduling code.  */
 207     void (* md_init) (FILE *, int, int);
 208
 209     /* Finalize machine-dependent scheduling code.  */
 210     void (* md_finish) (FILE *, int);
 211
 212     /* Initialize machine-dependent function while scheduling code.  */
 213     void (* md_init_global) (FILE *, int, int);
 214
 215     /* Finalize machine-dependent function wide scheduling code.  */
 216     void (* md_finish_global) (FILE *, int);
 217
 218     /* Reorder insns in a machine-dependent fashion, in two different
 219        places.  Default does nothing.  */
 220     int (* reorder) (FILE *, int, rtx *, int *, int);
 221     int (* reorder2) (FILE *, int, rtx *, int *, int);
 222
 223     /* The following member value is a pointer to a function called
 224        after evaluation forward dependencies of insns in chain given
 225        by two parameter values (head and tail correspondingly).  */
 226     void (* dependencies_evaluation_hook) (rtx, rtx);
 227
 228     /* The values of the following four members are pointers to
 229        functions used to simplify the automaton descriptions.
 230        dfa_pre_cycle_insn and dfa_post_cycle_insn give functions
 231        returning insns which are used to change the pipeline hazard
 232        recognizer state when the new simulated processor cycle
 233        correspondingly starts and finishes.  The function defined by
 234        init_dfa_pre_cycle_insn and init_dfa_post_cycle_insn are used
 235        to initialize the corresponding insns.  The default values of
 236        the members result in not changing the automaton state when
 237        the new simulated processor cycle correspondingly starts and
 238        finishes.  */
 239     void (* init_dfa_pre_cycle_insn) (void);
 240     rtx (* dfa_pre_cycle_insn) (void);
 241     void (* init_dfa_post_cycle_insn) (void);
 242     rtx (* dfa_post_cycle_insn) (void);
 243
 244     /* The following member value is a pointer to a function returning value
 245        which defines how many insns in queue `ready' will we try for
 246        multi-pass scheduling.  If the member value is nonzero and the
 247        function returns positive value, the DFA based scheduler will make
 248        multi-pass scheduling for the first cycle.  In other words, we will
 249        try to choose ready insn which permits to start maximum number of
 250        insns on the same cycle.  */
 251     int (* first_cycle_multipass_dfa_lookahead) (void);
 252
 253     /* The following member value is pointer to a function controlling
 254        what insns from the ready insn queue will be considered for the
 255        multipass insn scheduling.  If the hook returns zero for insn
 256        passed as the parameter, the insn will be not chosen to be
 257        issued.  */
 258     int (* first_cycle_multipass_dfa_lookahead_guard) (rtx);
 259
 260     /* The following member value is pointer to a function called by
 261        the insn scheduler before issuing insn passed as the third
 262        parameter on given cycle.  If the hook returns nonzero, the
 263        insn is not issued on given processors cycle.  Instead of that,
 264        the processor cycle is advanced.  If the value passed through
 265        the last parameter is zero, the insn ready queue is not sorted
 266        on the new cycle start as usually.  The first parameter passes
 267        file for debugging output.  The second one passes the scheduler
 268        verbose level of the debugging output.  The forth and the fifth
 269        parameter values are correspondingly processor cycle on which
 270        the previous insn has been issued and the current processor
 271        cycle.  */
 272     int (* dfa_new_cycle) (FILE *, int, rtx, int, int, int *);
 273
 274     /* The following member value is a pointer to a function called
 275        by the insn scheduler.  It should return true if there exists a
 276        dependence which is considered costly by the target, between
 277        the insn passed as the first parameter, and the insn passed as
 278        the second parameter.  The third parameter is the INSN_DEPEND
 279        link that represents the dependence between the two insns.  The
 280        fourth argument is the cost of the dependence as estimated by
 281        the scheduler.  The last argument is the distance in cycles
 282        between the already scheduled insn (first parameter) and the
 283        the second insn (second parameter).  */
 284     bool (* is_costly_dependence) (rtx, rtx, rtx, int, int);
 285   } sched;
 286
 287   /* Functions relating to vectorization.  */
 288   struct vectorize
 289   {
 290     /* The following member value is a pointer to a function called
 291        by the vectorizer, and return the decl of the target builtin
 292        function.  */
 293     tree (* builtin_mask_for_load) (void);
 294   } vectorize;
 295
 296   /* The initial value of target_flags.  */
 297   int default_target_flags;
 298
 299   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
 300      passed to the switch; it is NULL if no argument was.  VALUE is the
 301      value of ARG if CODE specifies a UInteger option, otherwise it is
 302      1 if the positive form of the switch was used and 0 if the negative
 303      form was.  Return true if the switch was valid.  */
 304   bool (* handle_option) (size_t code, const char *arg, int value);
 305
 306   /* Return machine mode for filter value.  */
 307   enum machine_mode (* eh_return_filter_mode) (void);
 308
 309   /* Given two decls, merge their attributes and return the result.  */
 310   tree (* merge_decl_attributes) (tree, tree);
 311
 312   /* Given two types, merge their attributes and return the result.  */
 313   tree (* merge_type_attributes) (tree, tree);
 314
 315   /* Table of machine attributes and functions to handle them.
 316      Ignored if NULL.  */
 317   const struct attribute_spec *attribute_table;
 318
 319   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 320      one if they are compatible and two if they are nearly compatible
 321      (which causes a warning to be generated).  */
 322   int (* comp_type_attributes) (tree type1, tree type2);
 323
 324   /* Assign default attributes to the newly defined TYPE.  */
 325   void (* set_default_type_attributes) (tree type);
 326
 327   /* Insert attributes on the newly created DECL.  */
 328   void (* insert_attributes) (tree decl, tree *attributes);
 329
 330   /* Return true if FNDECL (which has at least one machine attribute)
 331      can be inlined despite its machine attributes, false otherwise.  */
 332   bool (* function_attribute_inlinable_p) (tree fndecl);
 333
 334   /* Return true if bitfields in RECORD_TYPE should follow the
 335      Microsoft Visual C++ bitfield layout rules.  */
 336   bool (* ms_bitfield_layout_p) (tree record_type);
 337
 338   /* Return true if anonymous bitfields affect structure alignment.  */
 339   bool (* align_anon_bitfield) (void);
 340
 341   /* Set up target-specific built-in functions.  */
 342   void (* init_builtins) (void);
 343
 344   /* Expand a target-specific builtin.  */
 345   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 346                           enum machine_mode mode, int ignore);
 347
 348   /* Fold a target-specific builtin.  */
 349   tree (* fold_builtin) (tree fndecl, tree arglist, bool ignore);
 350
 351   /* For a vendor-specific fundamental TYPE, return a pointer to
 352      a statically-allocated string containing the C++ mangling for
 353      TYPE.  In all other cases, return NULL.  */
 354   const char * (* mangle_fundamental_type) (tree type);
 355
 356   /* Make any adjustments to libfunc names needed for this target.  */
 357   void (* init_libfuncs) (void);
 358
 359   /* Given a decl, a section name, and whether the decl initializer
 360      has relocs, choose attributes for the section.  */
 361   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 362   unsigned int (* section_type_flags) (tree, const char *, int);
 363
 364   /* True if new jumps cannot be created, to replace existing ones or
 365      not, at the current point in the compilation.  */
 366   bool (* cannot_modify_jumps_p) (void);
 367
 368   /* Return a register class for which branch target register
 369      optimizations should be applied.  */
 370   int (* branch_target_register_class) (void);
 371
 372   /* Return true if branch target register optimizations should include
 373      callee-saved registers that are not already live during the current
 374      function.  AFTER_PE_GEN is true if prologues and epilogues have
 375      already been generated.  */
 376   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 377
 378   /* True if the constant X cannot be placed in the constant pool.  */
 379   bool (* cannot_force_const_mem) (rtx);
 380
 381   /* True if the insn X cannot be duplicated.  */
 382   bool (* cannot_copy_insn_p) (rtx);
 383
 384   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 385   rtx (* delegitimize_address) (rtx);
 386
 387   /* True if it is OK to do sibling call optimization for the specified
 388      call expression EXP.  DECL will be the called function, or NULL if
 389      this is an indirect call.  */
 390   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 391
 392   /* True if EXP should be placed in a "small data" section.  */
 393   bool (* in_small_data_p) (tree);
 394
 395   /* True if EXP names an object for which name resolution must resolve
 396      to the current module.  */
 397   bool (* binds_local_p) (tree);
 398
 399   /* Do something target-specific to record properties of the DECL into
 400      the associated SYMBOL_REF.  */
 401   void (* encode_section_info) (tree, rtx, int);
 402
 403   /* Undo the effects of encode_section_info on the symbol string.  */
 404   const char * (* strip_name_encoding) (const char *);
 405
 406   /* If shift optabs for MODE are known to always truncate the shift count,
 407      return the mask that they apply.  Return 0 otherwise.  */
 408   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
 409
 410   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 411   bool (* valid_pointer_mode) (enum machine_mode mode);
 412
 413   /* True if MODE is valid for the target.  By "valid", we mean able to
 414      be manipulated in non-trivial ways.  In particular, this means all
 415      the arithmetic is supported.  */
 416   bool (* scalar_mode_supported_p) (enum machine_mode mode);
 417
 418   /* Similarly for vector modes.  "Supported" here is less strict.  At
 419      least some operations are supported; need to check optabs or builtins
 420      for further details.  */
 421   bool (* vector_mode_supported_p) (enum machine_mode mode);
 422
 423   /* True if a vector is opaque.  */
 424   bool (* vector_opaque_p) (tree);
 425
 426   /* Compute a (partial) cost for rtx X.  Return true if the complete
 427      cost has been computed, and false if subexpressions should be
 428      scanned.  In either case, *TOTAL contains the cost result.  */
 429   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 430      not necessarily defined at this point.  */
 431   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 432
 433   /* Compute the cost of X, used as an address.  Never called with
 434      invalid addresses.  */
 435   int (* address_cost) (rtx x);
 436
 437   /* Given a register, this hook should return a parallel of registers
 438      to represent where to find the register pieces.  Define this hook
 439      if the register and its mode are represented in Dwarf in
 440      non-contiguous locations, or if the register should be
 441      represented in more than one register in Dwarf.  Otherwise, this
 442      hook should return NULL_RTX.  */
 443   rtx (* dwarf_register_span) (rtx);
 444
 445   /* Fetch the fixed register(s) which hold condition codes, for
 446      targets where it makes sense to look for duplicate assignments to
 447      the condition codes.  This should return true if there is such a
 448      register, false otherwise.  The arguments should be set to the
 449      fixed register numbers.  Up to two condition code registers are
 450      supported.  If there is only one for this target, the int pointed
 451      at by the second argument should be set to -1.  */
 452   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 453
 454   /* If two condition code modes are compatible, return a condition
 455      code mode which is compatible with both, such that a comparison
 456      done in the returned mode will work for both of the original
 457      modes.  If the condition code modes are not compatible, return
 458      VOIDmode.  */
 459   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 460                                              enum machine_mode);
 461
 462   /* Do machine-dependent code transformations.  Called just before
 463      delayed-branch scheduling.  */
 464   void (* machine_dependent_reorg) (void);
 465
 466   /* Create the __builtin_va_list type.  */
 467   tree (* build_builtin_va_list) (void);
 468
 469   /* Gimplifies a VA_ARG_EXPR.  */
 470   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 471                                  tree *post_p);
 472
 473   /* Validity-checking routines for PCH files, target-specific.
 474      get_pch_validity returns a pointer to the data to be stored,
 475      and stores the size in its argument.  pch_valid_p gets the same
 476      information back and returns NULL if the PCH is valid,
 477      or an error message if not.
 478   */
 479   void * (* get_pch_validity) (size_t *);
 480   const char * (* pch_valid_p) (const void *, size_t);
 481
 482   /* True if the compiler should give an enum type only as many
 483      bytes as it takes to represent the range of possible values of
 484      that type.  */
 485   bool (* default_short_enums) (void);
 486
 487   /* This target hook returns an rtx that is used to store the address
 488      of the current frame into the built-in setjmp buffer.  */
 489   rtx (* builtin_setjmp_frame_value) (void);
 490
 491   /* This target hook should add STRING_CST trees for any hard regs
 492      the port wishes to automatically clobber for an asm.  */
 493   tree (* md_asm_clobbers) (tree, tree, tree);
 494
 495   /* This target hook allows the backend to specify a calling convention
 496      in the debug information.  This function actually returns an
 497      enum dwarf_calling_convention, but because of forward declarations
 498      and not wanting to include dwarf2.h everywhere target.h is included
 499      the function is being declared as an int.  */
 500   int (* dwarf_calling_convention) (tree);
 501
 502   /* This target hook allows the backend to emit frame-related insns that
 503      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
 504      engine will invoke it on insns of the form
 505        (set (reg) (unspec [...] UNSPEC_INDEX))
 506      and
 507        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
 508      to let the backend emit the call frame instructions.  */
 509   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
 510
 511   /* Perform architecture specific checking of statements gimplified
 512      from VA_ARG_EXPR.  LHS is left hand side of MODIFY_EXPR, RHS
 513      is right hand side.  Returns true if the statements doesn't need
 514      to be checked for va_list references.  */
 515   bool (*stdarg_optimize_hook) (struct stdarg_info *ai, tree lhs, tree rhs);
 516
 517   /* Functions relating to calls - argument passing, returns, etc.  */
 518   struct calls {
 519     bool (*promote_function_args) (tree fntype);
 520     bool (*promote_function_return) (tree fntype);
 521     bool (*promote_prototypes) (tree fntype);
 522     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 523     bool (*return_in_memory) (tree type, tree fndecl);
 524     bool (*return_in_msb) (tree type);
 525
 526     /* Return true if a parameter must be passed by reference.  TYPE may
 527        be null if this is a libcall.  CA may be null if this query is
 528        from __builtin_va_arg.  */
 529     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 530                                tree type, bool named_arg);
 531
 532     rtx (*expand_builtin_saveregs) (void);
 533     /* Returns pretend_argument_size.  */
 534     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 535                                     tree type, int *pretend_arg_size,
 536                                     int second_time);
 537     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 538     /* Returns true if we should use
 539        targetm.calls.setup_incoming_varargs() and/or
 540        targetm.calls.strict_argument_naming().  */
 541     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 542
 543     /* Given a complex type T, return true if a parameter of type T
 544        should be passed as two scalars.  */
 545     bool (* split_complex_arg) (tree type);
 546
 547     /* Return true if type T, mode MODE, may not be passed in registers,
 548        but must be passed on the stack.  */
 549     /* ??? This predicate should be applied strictly after pass-by-reference.
 550        Need audit to verify that this is the case.  */
 551     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 552
 553     /* Return true if type TYPE, mode MODE, which is passed by reference,
 554        should have the object copy generated by the callee rather than
 555        the caller.  It is never called for TYPE requiring constructors.  */
 556     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 557                             tree type, bool named);
 558
 559     /* Return zero for arguments passed entirely on the stack or entirely
 560        in registers.  If passed in both, return the number of bytes passed
 561        in registers; the balance is therefore passed on the stack.  */
 562     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 563                                tree type, bool named);
 564
 565     /* Return the diagnostic message string if function without a prototype
 566        is not allowed for this 'val' argument; NULL otherwise. */
 567     const char *(*invalid_arg_for_unprototyped_fn) (tree typelist,
 568                                                     tree funcdecl, tree val);
 569   } calls;
 570
 571   /* Functions specific to the C++ frontend.  */
 572   struct cxx {
 573     /* Return the integer type used for guard variables.  */
 574     tree (*guard_type) (void);
 575     /* Return true if only the low bit of the guard should be tested.  */
 576     bool (*guard_mask_bit) (void);
 577     /* Returns the size of the array cookie for an array of type.  */
 578     tree (*get_cookie_size) (tree);
 579     /* Returns true if the element size should be stored in the
 580        array cookie.  */
 581     bool (*cookie_has_size) (void);
 582     /* Allows backends to perform additional processing when
 583        deciding if a class should be exported or imported.  */
 584     int (*import_export_class) (tree, int);
 585     /* Returns true if constructors and destructors return "this".  */
 586     bool (*cdtor_returns_this) (void);
 587     /* Returns true if the key method for a class can be an inline
 588        function, so long as it is not declared inline in the class
 589        itself.  Returning true is the behavior required by the Itanium
 590        C++ ABI.  */
 591     bool (*key_method_may_be_inline) (void);
 592     /* DECL is a virtual table, virtual table table, typeinfo object,
 593        or other similar implicit class data object that will be
 594        emitted with external linkage in this translation unit.  No ELF
 595        visibility has been explicitly specified.  If the target needs
 596        to specify a visibility other than that of the containing class,
 597        use this hook to set DECL_VISIBILITY and
 598        DECL_VISIBILITY_SPECIFIED.  */
 599     void (*determine_class_data_visibility) (tree decl);
 600     /* Returns true (the default) if virtual tables and other
 601        similar implicit class data objects are always COMDAT if they
 602        have external linkage.  If this hook returns false, then
 603        class data for classes whose virtual table will be emitted in
 604        only one translation unit will not be COMDAT.  */
 605     bool (*class_data_always_comdat) (void);
 606     /* Returns true if __aeabi_atexit should be used to register static
 607        destructors.  */
 608     bool (*use_aeabi_atexit) (void);
 609   } cxx;
 610
 611   /* Leave the boolean fields at the end.  */
 612
 613   /* True if arbitrary sections are supported.  */
 614   bool have_named_sections;
 615
 616   /* True if "native" constructors and destructors are supported,
 617      false if we're using collect2 for the job.  */
 618   bool have_ctors_dtors;
 619
 620   /* True if thread-local storage is supported.  */
 621   bool have_tls;
 622
 623   /* True if a small readonly data section is supported.  */
 624   bool have_srodata_section;
 625
 626   /* True if EH frame info sections should be zero-terminated.  */
 627   bool terminate_dw2_eh_frame_info;
 628
 629   /* True if #NO_APP should be emitted at the beginning of
 630      assembly output.  */
 631   bool file_start_app_off;
 632
 633   /* True if output_file_directive should be called for main_input_filename
 634      at the beginning of assembly output.  */
 635   bool file_start_file_directive;
 636
 637   /* True if #pragma redefine_extname is to be supported.  */
 638   bool handle_pragma_redefine_extname;
 639
 640   /* True if #pragma extern_prefix is to be supported.  */
 641   bool handle_pragma_extern_prefix;
 642
 643   /* True if the target is allowed to reorder memory accesses unless
 644      synchronization is explicitly requested.  */
 645   bool relaxed_ordering;
 646
 647   /* Leave the boolean fields at the end.  */
 648 };
 649
 650 extern struct gcc_target targetm;
 651
 652 #endif /* GCC_TARGET_H */