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, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, 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 /* The struct used by the secondary_reload target hook.  */
  56 typedef struct secondary_reload_info
  57 {
  58   /* icode is actually an enum insn_code, but we don't want to force every
  59      file that includes target.h to include optabs.h .  */
  60   int icode;
  61   int extra_cost; /* Cost for using (a) scratch register(s) to be taken
  62                      into account by copy_cost.  */
  63   /* The next two members are for the use of the backward
  64      compatibility hook.  */
  65   struct secondary_reload_info *prev_sri;
  66   int t_icode; /* Actually an enum insn_code - see above.  */
  67 } secondary_reload_info;
  68
  69
  70 struct gcc_target
  71 {
  72   /* Functions that output assembler for the target.  */
  73   struct asm_out
  74   {
  75     /* Opening and closing parentheses for asm expression grouping.  */
  76     const char *open_paren, *close_paren;
  77
  78     /* Assembler instructions for creating various kinds of integer object.  */
  79     const char *byte_op;
  80     struct asm_int_op
  81     {
  82       const char *hi;
  83       const char *si;
  84       const char *di;
  85       const char *ti;
  86     } aligned_op, unaligned_op;
  87
  88     /* Try to output the assembler code for an integer object whose
  89        value is given by X.  SIZE is the size of the object in bytes and
  90        ALIGNED_P indicates whether it is aligned.  Return true if
  91        successful.  Only handles cases for which BYTE_OP, ALIGNED_OP
  92        and UNALIGNED_OP are NULL.  */
  93     bool (* integer) (rtx x, unsigned int size, int aligned_p);
  94
  95     /* Output code that will globalize a label.  */
  96     void (* globalize_label) (FILE *, const char *);
  97
  98     /* Output code that will emit a label for unwind info, if this
  99        target requires such labels.  Second argument is the decl the
 100        unwind info is associated with, third is a boolean: true if
 101        this is for exception handling, fourth is a boolean: true if
 102        this is only a placeholder for an omitted FDE.  */
 103     void (* unwind_label) (FILE *, tree, int, int);
 104
 105     /* Emit any directives required to unwind this instruction.  */
 106     void (* unwind_emit) (FILE *, rtx);
 107
 108     /* Output an internal label.  */
 109     void (* internal_label) (FILE *, const char *, unsigned long);
 110
 111     /* Emit a ttype table reference to a typeinfo object.  */
 112     bool (* ttype) (rtx);
 113
 114     /* Emit an assembler directive to set visibility for the symbol
 115        associated with the tree decl.  */
 116     void (* visibility) (tree, int);
 117
 118     /* Output the assembler code for entry to a function.  */
 119     void (* function_prologue) (FILE *, HOST_WIDE_INT);
 120
 121     /* Output the assembler code for end of prologue.  */
 122     void (* function_end_prologue) (FILE *);
 123
 124     /* Output the assembler code for start of epilogue.  */
 125     void (* function_begin_epilogue) (FILE *);
 126
 127     /* Output the assembler code for function exit.  */
 128     void (* function_epilogue) (FILE *, HOST_WIDE_INT);
 129
 130     /* Initialize target-specific sections.  */
 131     void (* init_sections) (void);
 132
 133     /* Tell assembler to change to section NAME with attributes FLAGS.
 134        If DECL is non-NULL, it is the VAR_DECL or FUNCTION_DECL with
 135        which this section is associated.  */
 136     void (* named_section) (const char *name, unsigned int flags, tree decl);
 137
 138     /* Return a section for EXP.  It may be a DECL or a constant.  RELOC
 139        is nonzero if runtime relocations must be applied; bit 1 will be
 140        set if the runtime relocations require non-local name resolution.
 141        ALIGN is the required alignment of the data.  */
 142     section *(* select_section) (tree, int, unsigned HOST_WIDE_INT);
 143
 144     /* Return a section for X.  MODE is X's mode and ALIGN is its
 145        alignment in bits.  */
 146     section *(* select_rtx_section) (enum machine_mode, rtx,
 147                                      unsigned HOST_WIDE_INT);
 148
 149     /* Select a unique section name for DECL.  RELOC is the same as
 150        for SELECT_SECTION.  */
 151     void (* unique_section) (tree, int);
 152
 153     /* Return the readonly data section associated with function DECL.  */
 154     section *(* function_rodata_section) (tree);
 155
 156     /* Output a constructor for a symbol with a given priority.  */
 157     void (* constructor) (rtx, int);
 158
 159     /* Output a destructor for a symbol with a given priority.  */
 160     void (* destructor) (rtx, int);
 161
 162     /* Output the assembler code for a thunk function.  THUNK_DECL is the
 163        declaration for the thunk function itself, FUNCTION is the decl for
 164        the target function.  DELTA is an immediate constant offset to be
 165        added to THIS.  If VCALL_OFFSET is nonzero, the word at
 166        *(*this + vcall_offset) should be added to THIS.  */
 167     void (* output_mi_thunk) (FILE *file, tree thunk_decl,
 168                               HOST_WIDE_INT delta, HOST_WIDE_INT vcall_offset,
 169                               tree function_decl);
 170
 171     /* Determine whether output_mi_thunk would succeed.  */
 172     /* ??? Ideally, this hook would not exist, and success or failure
 173        would be returned from output_mi_thunk directly.  But there's
 174        too much undo-able setup involved in invoking output_mi_thunk.
 175        Could be fixed by making output_mi_thunk emit rtl instead of
 176        text to the output file.  */
 177     bool (* can_output_mi_thunk) (tree thunk_decl, HOST_WIDE_INT delta,
 178                                   HOST_WIDE_INT vcall_offset,
 179                                   tree function_decl);
 180
 181     /* Output any boilerplate text needed at the beginning of a
 182        translation unit.  */
 183     void (*file_start) (void);
 184
 185     /* Output any boilerplate text needed at the end of a
 186        translation unit.  */
 187     void (*file_end) (void);
 188
 189     /* Output an assembler pseudo-op to declare a library function name
 190        external.  */
 191     void (*external_libcall) (rtx);
 192
 193      /* Output an assembler directive to mark decl live. This instructs
 194         linker to not dead code strip this symbol.  */
 195     void (*mark_decl_preserved) (const char *);
 196
 197     /* Output a DTP-relative reference to a TLS symbol.  */
 198     void (*output_dwarf_dtprel) (FILE *file, int size, rtx x);
 199
 200   } asm_out;
 201
 202   /* Functions relating to instruction scheduling.  */
 203   struct sched
 204   {
 205     /* Given the current cost, COST, of an insn, INSN, calculate and
 206        return a new cost based on its relationship to DEP_INSN through
 207        the dependence LINK.  The default is to make no adjustment.  */
 208     int (* adjust_cost) (rtx insn, rtx link, rtx def_insn, int cost);
 209
 210     /* Adjust the priority of an insn as you see fit.  Returns the new
 211        priority.  */
 212     int (* adjust_priority) (rtx, int);
 213
 214     /* Function which returns the maximum number of insns that can be
 215        scheduled in the same machine cycle.  This must be constant
 216        over an entire compilation.  The default is 1.  */
 217     int (* issue_rate) (void);
 218
 219     /* Calculate how much this insn affects how many more insns we
 220        can emit this cycle.  Default is they all cost the same.  */
 221     int (* variable_issue) (FILE *, int, rtx, int);
 222
 223     /* Initialize machine-dependent scheduling code.  */
 224     void (* md_init) (FILE *, int, int);
 225
 226     /* Finalize machine-dependent scheduling code.  */
 227     void (* md_finish) (FILE *, int);
 228
 229     /* Initialize machine-dependent function while scheduling code.  */
 230     void (* md_init_global) (FILE *, int, int);
 231
 232     /* Finalize machine-dependent function wide scheduling code.  */
 233     void (* md_finish_global) (FILE *, int);
 234
 235     /* Reorder insns in a machine-dependent fashion, in two different
 236        places.  Default does nothing.  */
 237     int (* reorder) (FILE *, int, rtx *, int *, int);
 238     int (* reorder2) (FILE *, int, rtx *, int *, int);
 239
 240     /* The following member value is a pointer to a function called
 241        after evaluation forward dependencies of insns in chain given
 242        by two parameter values (head and tail correspondingly).  */
 243     void (* dependencies_evaluation_hook) (rtx, rtx);
 244
 245     /* The values of the following four members are pointers to
 246        functions used to simplify the automaton descriptions.
 247        dfa_pre_cycle_insn and dfa_post_cycle_insn give functions
 248        returning insns which are used to change the pipeline hazard
 249        recognizer state when the new simulated processor cycle
 250        correspondingly starts and finishes.  The function defined by
 251        init_dfa_pre_cycle_insn and init_dfa_post_cycle_insn are used
 252        to initialize the corresponding insns.  The default values of
 253        the members result in not changing the automaton state when
 254        the new simulated processor cycle correspondingly starts and
 255        finishes.  */
 256     void (* init_dfa_pre_cycle_insn) (void);
 257     rtx (* dfa_pre_cycle_insn) (void);
 258     void (* init_dfa_post_cycle_insn) (void);
 259     rtx (* dfa_post_cycle_insn) (void);
 260
 261     /* The following member value is a pointer to a function returning value
 262        which defines how many insns in queue `ready' will we try for
 263        multi-pass scheduling.  If the member value is nonzero and the
 264        function returns positive value, the DFA based scheduler will make
 265        multi-pass scheduling for the first cycle.  In other words, we will
 266        try to choose ready insn which permits to start maximum number of
 267        insns on the same cycle.  */
 268     int (* first_cycle_multipass_dfa_lookahead) (void);
 269
 270     /* The following member value is pointer to a function controlling
 271        what insns from the ready insn queue will be considered for the
 272        multipass insn scheduling.  If the hook returns zero for insn
 273        passed as the parameter, the insn will be not chosen to be
 274        issued.  */
 275     int (* first_cycle_multipass_dfa_lookahead_guard) (rtx);
 276
 277     /* The following member value is pointer to a function called by
 278        the insn scheduler before issuing insn passed as the third
 279        parameter on given cycle.  If the hook returns nonzero, the
 280        insn is not issued on given processors cycle.  Instead of that,
 281        the processor cycle is advanced.  If the value passed through
 282        the last parameter is zero, the insn ready queue is not sorted
 283        on the new cycle start as usually.  The first parameter passes
 284        file for debugging output.  The second one passes the scheduler
 285        verbose level of the debugging output.  The forth and the fifth
 286        parameter values are correspondingly processor cycle on which
 287        the previous insn has been issued and the current processor
 288        cycle.  */
 289     int (* dfa_new_cycle) (FILE *, int, rtx, int, int, int *);
 290
 291     /* The following member value is a pointer to a function called
 292        by the insn scheduler.  It should return true if there exists a
 293        dependence which is considered costly by the target, between
 294        the insn passed as the first parameter, and the insn passed as
 295        the second parameter.  The third parameter is the INSN_DEPEND
 296        link that represents the dependence between the two insns.  The
 297        fourth argument is the cost of the dependence as estimated by
 298        the scheduler.  The last argument is the distance in cycles
 299        between the already scheduled insn (first parameter) and the
 300        the second insn (second parameter).  */
 301     bool (* is_costly_dependence) (rtx, rtx, rtx, int, int);
 302   } sched;
 303
 304   /* Functions relating to vectorization.  */
 305   struct vectorize
 306   {
 307     /* The following member value is a pointer to a function called
 308        by the vectorizer, and return the decl of the target builtin
 309        function.  */
 310     tree (* builtin_mask_for_load) (void);
 311   } vectorize;
 312
 313   /* The initial value of target_flags.  */
 314   int default_target_flags;
 315
 316   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
 317      passed to the switch; it is NULL if no argument was.  VALUE is the
 318      value of ARG if CODE specifies a UInteger option, otherwise it is
 319      1 if the positive form of the switch was used and 0 if the negative
 320      form was.  Return true if the switch was valid.  */
 321   bool (* handle_option) (size_t code, const char *arg, int value);
 322
 323   /* Return machine mode for filter value.  */
 324   enum machine_mode (* eh_return_filter_mode) (void);
 325
 326   /* Given two decls, merge their attributes and return the result.  */
 327   tree (* merge_decl_attributes) (tree, tree);
 328
 329   /* Given two types, merge their attributes and return the result.  */
 330   tree (* merge_type_attributes) (tree, tree);
 331
 332   /* Table of machine attributes and functions to handle them.
 333      Ignored if NULL.  */
 334   const struct attribute_spec *attribute_table;
 335
 336   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 337      one if they are compatible and two if they are nearly compatible
 338      (which causes a warning to be generated).  */
 339   int (* comp_type_attributes) (tree type1, tree type2);
 340
 341   /* Assign default attributes to the newly defined TYPE.  */
 342   void (* set_default_type_attributes) (tree type);
 343
 344   /* Insert attributes on the newly created DECL.  */
 345   void (* insert_attributes) (tree decl, tree *attributes);
 346
 347   /* Return true if FNDECL (which has at least one machine attribute)
 348      can be inlined despite its machine attributes, false otherwise.  */
 349   bool (* function_attribute_inlinable_p) (tree fndecl);
 350
 351   /* Return true if bitfields in RECORD_TYPE should follow the
 352      Microsoft Visual C++ bitfield layout rules.  */
 353   bool (* ms_bitfield_layout_p) (tree record_type);
 354
 355   /* Return true if anonymous bitfields affect structure alignment.  */
 356   bool (* align_anon_bitfield) (void);
 357
 358   /* Set up target-specific built-in functions.  */
 359   void (* init_builtins) (void);
 360
 361   /* Expand a target-specific builtin.  */
 362   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 363                           enum machine_mode mode, int ignore);
 364
 365   /* Select a replacement for a target-specific builtin.  This is done
 366      *before* regular type checking, and so allows the target to implement
 367      a crude form of function overloading.  The result is a complete
 368      expression that implements the operation.  */
 369   tree (*resolve_overloaded_builtin) (tree decl, tree params);
 370
 371   /* Fold a target-specific builtin.  */
 372   tree (* fold_builtin) (tree fndecl, tree arglist, bool ignore);
 373
 374   /* For a vendor-specific fundamental TYPE, return a pointer to
 375      a statically-allocated string containing the C++ mangling for
 376      TYPE.  In all other cases, return NULL.  */
 377   const char * (* mangle_fundamental_type) (tree type);
 378
 379   /* Make any adjustments to libfunc names needed for this target.  */
 380   void (* init_libfuncs) (void);
 381
 382   /* Given a decl, a section name, and whether the decl initializer
 383      has relocs, choose attributes for the section.  */
 384   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 385   unsigned int (* section_type_flags) (tree, const char *, int);
 386
 387   /* True if new jumps cannot be created, to replace existing ones or
 388      not, at the current point in the compilation.  */
 389   bool (* cannot_modify_jumps_p) (void);
 390
 391   /* Return a register class for which branch target register
 392      optimizations should be applied.  */
 393   int (* branch_target_register_class) (void);
 394
 395   /* Return true if branch target register optimizations should include
 396      callee-saved registers that are not already live during the current
 397      function.  AFTER_PE_GEN is true if prologues and epilogues have
 398      already been generated.  */
 399   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 400
 401   /* True if the constant X cannot be placed in the constant pool.  */
 402   bool (* cannot_force_const_mem) (rtx);
 403
 404   /* True if the insn X cannot be duplicated.  */
 405   bool (* cannot_copy_insn_p) (rtx);
 406
 407   /* True if X is considered to be commutative.  */
 408   bool (* commutative_p) (rtx, int);
 409
 410   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 411   rtx (* delegitimize_address) (rtx);
 412
 413   /* True if it is OK to do sibling call optimization for the specified
 414      call expression EXP.  DECL will be the called function, or NULL if
 415      this is an indirect call.  */
 416   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 417
 418   /* True if EXP should be placed in a "small data" section.  */
 419   bool (* in_small_data_p) (tree);
 420
 421   /* True if EXP names an object for which name resolution must resolve
 422      to the current module.  */
 423   bool (* binds_local_p) (tree);
 424
 425   /* Do something target-specific to record properties of the DECL into
 426      the associated SYMBOL_REF.  */
 427   void (* encode_section_info) (tree, rtx, int);
 428
 429   /* Undo the effects of encode_section_info on the symbol string.  */
 430   const char * (* strip_name_encoding) (const char *);
 431
 432   /* If shift optabs for MODE are known to always truncate the shift count,
 433      return the mask that they apply.  Return 0 otherwise.  */
 434   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
 435
 436   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 437   bool (* valid_pointer_mode) (enum machine_mode mode);
 438
 439   /* True if MODE is valid for the target.  By "valid", we mean able to
 440      be manipulated in non-trivial ways.  In particular, this means all
 441      the arithmetic is supported.  */
 442   bool (* scalar_mode_supported_p) (enum machine_mode mode);
 443
 444   /* Similarly for vector modes.  "Supported" here is less strict.  At
 445      least some operations are supported; need to check optabs or builtins
 446      for further details.  */
 447   bool (* vector_mode_supported_p) (enum machine_mode mode);
 448
 449   /* True if a vector is opaque.  */
 450   bool (* vector_opaque_p) (tree);
 451
 452   /* Compute a (partial) cost for rtx X.  Return true if the complete
 453      cost has been computed, and false if subexpressions should be
 454      scanned.  In either case, *TOTAL contains the cost result.  */
 455   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 456      not necessarily defined at this point.  */
 457   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 458
 459   /* Compute the cost of X, used as an address.  Never called with
 460      invalid addresses.  */
 461   int (* address_cost) (rtx x);
 462
 463   /* Return where to allocate pseudo for a given hard register initial
 464      value.  */
 465   rtx (* allocate_initial_value) (rtx x);
 466
 467   /* Given a register, this hook should return a parallel of registers
 468      to represent where to find the register pieces.  Define this hook
 469      if the register and its mode are represented in Dwarf in
 470      non-contiguous locations, or if the register should be
 471      represented in more than one register in Dwarf.  Otherwise, this
 472      hook should return NULL_RTX.  */
 473   rtx (* dwarf_register_span) (rtx);
 474
 475   /* Fetch the fixed register(s) which hold condition codes, for
 476      targets where it makes sense to look for duplicate assignments to
 477      the condition codes.  This should return true if there is such a
 478      register, false otherwise.  The arguments should be set to the
 479      fixed register numbers.  Up to two condition code registers are
 480      supported.  If there is only one for this target, the int pointed
 481      at by the second argument should be set to -1.  */
 482   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 483
 484   /* If two condition code modes are compatible, return a condition
 485      code mode which is compatible with both, such that a comparison
 486      done in the returned mode will work for both of the original
 487      modes.  If the condition code modes are not compatible, return
 488      VOIDmode.  */
 489   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 490                                              enum machine_mode);
 491
 492   /* Do machine-dependent code transformations.  Called just before
 493      delayed-branch scheduling.  */
 494   void (* machine_dependent_reorg) (void);
 495
 496   /* Create the __builtin_va_list type.  */
 497   tree (* build_builtin_va_list) (void);
 498
 499   /* Gimplifies a VA_ARG_EXPR.  */
 500   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 501                                  tree *post_p);
 502
 503   /* Validity-checking routines for PCH files, target-specific.
 504      get_pch_validity returns a pointer to the data to be stored,
 505      and stores the size in its argument.  pch_valid_p gets the same
 506      information back and returns NULL if the PCH is valid,
 507      or an error message if not.
 508   */
 509   void * (* get_pch_validity) (size_t *);
 510   const char * (* pch_valid_p) (const void *, size_t);
 511
 512   /* If nonnull, this function checks whether a PCH file with the
 513      given set of target flags can be used.  It returns NULL if so,
 514      otherwise it returns an error message.  */
 515   const char *(*check_pch_target_flags) (int);
 516
 517   /* True if the compiler should give an enum type only as many
 518      bytes as it takes to represent the range of possible values of
 519      that type.  */
 520   bool (* default_short_enums) (void);
 521
 522   /* This target hook returns an rtx that is used to store the address
 523      of the current frame into the built-in setjmp buffer.  */
 524   rtx (* builtin_setjmp_frame_value) (void);
 525
 526   /* This target hook should add STRING_CST trees for any hard regs
 527      the port wishes to automatically clobber for an asm.  */
 528   tree (* md_asm_clobbers) (tree, tree, tree);
 529
 530   /* This target hook allows the backend to specify a calling convention
 531      in the debug information.  This function actually returns an
 532      enum dwarf_calling_convention, but because of forward declarations
 533      and not wanting to include dwarf2.h everywhere target.h is included
 534      the function is being declared as an int.  */
 535   int (* dwarf_calling_convention) (tree);
 536
 537   /* This target hook allows the backend to emit frame-related insns that
 538      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
 539      engine will invoke it on insns of the form
 540        (set (reg) (unspec [...] UNSPEC_INDEX))
 541      and
 542        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
 543      to let the backend emit the call frame instructions.  */
 544   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
 545
 546   /* Perform architecture specific checking of statements gimplified
 547      from VA_ARG_EXPR.  LHS is left hand side of MODIFY_EXPR, RHS
 548      is right hand side.  Returns true if the statements doesn't need
 549      to be checked for va_list references.  */
 550   bool (* stdarg_optimize_hook) (struct stdarg_info *ai, tree lhs, tree rhs);
 551
 552   /* This target hook allows the operating system to override the DECL
 553      that represents the external variable that contains the stack
 554      protection guard variable.  The type of this DECL is ptr_type_node.  */
 555   tree (* stack_protect_guard) (void);
 556
 557   /* This target hook allows the operating system to override the CALL_EXPR
 558      that is invoked when a check vs the guard variable fails.  */
 559   tree (* stack_protect_fail) (void);
 560
 561   /* Returns NULL if target supports the insn within a doloop block,
 562      otherwise it returns an error message.  */
 563   const char * (*invalid_within_doloop) (rtx);
 564
 565   /* DECL is a variable or function with __attribute__((dllimport))
 566      specified.  Use this hook if the target needs to add extra validation
 567      checks to  handle_dll_attribute ().  */
 568   bool (* valid_dllimport_attribute_p) (tree decl);
 569
 570   /* Functions relating to calls - argument passing, returns, etc.  */
 571   struct calls {
 572     bool (*promote_function_args) (tree fntype);
 573     bool (*promote_function_return) (tree fntype);
 574     bool (*promote_prototypes) (tree fntype);
 575     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 576     bool (*return_in_memory) (tree type, tree fndecl);
 577     bool (*return_in_msb) (tree type);
 578
 579     /* Return true if a parameter must be passed by reference.  TYPE may
 580        be null if this is a libcall.  CA may be null if this query is
 581        from __builtin_va_arg.  */
 582     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 583                                tree type, bool named_arg);
 584
 585     rtx (*expand_builtin_saveregs) (void);
 586     /* Returns pretend_argument_size.  */
 587     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 588                                     tree type, int *pretend_arg_size,
 589                                     int second_time);
 590     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 591     /* Returns true if we should use
 592        targetm.calls.setup_incoming_varargs() and/or
 593        targetm.calls.strict_argument_naming().  */
 594     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 595
 596     /* Given a complex type T, return true if a parameter of type T
 597        should be passed as two scalars.  */
 598     bool (* split_complex_arg) (tree type);
 599
 600     /* Return true if type T, mode MODE, may not be passed in registers,
 601        but must be passed on the stack.  */
 602     /* ??? This predicate should be applied strictly after pass-by-reference.
 603        Need audit to verify that this is the case.  */
 604     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 605
 606     /* Return true if type TYPE, mode MODE, which is passed by reference,
 607        should have the object copy generated by the callee rather than
 608        the caller.  It is never called for TYPE requiring constructors.  */
 609     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 610                             tree type, bool named);
 611
 612     /* Return zero for arguments passed entirely on the stack or entirely
 613        in registers.  If passed in both, return the number of bytes passed
 614        in registers; the balance is therefore passed on the stack.  */
 615     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 616                                tree type, bool named);
 617
 618     /* Return the diagnostic message string if function without a prototype
 619        is not allowed for this 'val' argument; NULL otherwise. */
 620     const char *(*invalid_arg_for_unprototyped_fn) (tree typelist,
 621                                                     tree funcdecl, tree val);
 622
 623     /* Return an rtx for the return value location of the function
 624        specified by FN_DECL_OR_TYPE with a return type of RET_TYPE.  */
 625     rtx (*function_value) (tree ret_type, tree fn_decl_or_type,
 626                            bool outgoing);
 627
 628     /* Return an rtx for the argument pointer incoming to the
 629        current function.  */
 630     rtx (*internal_arg_pointer) (void);
 631   } calls;
 632
 633   /* Return the diagnostic message string if conversion from FROMTYPE
 634      to TOTYPE is not allowed, NULL otherwise.  */
 635   const char *(*invalid_conversion) (tree fromtype, tree totype);
 636
 637   /* Return the diagnostic message string if the unary operation OP is
 638      not permitted on TYPE, NULL otherwise.  */
 639   const char *(*invalid_unary_op) (int op, tree type);
 640
 641   /* Return the diagnostic message string if the binary operation OP
 642      is not permitted on TYPE1 and TYPE2, NULL otherwise.  */
 643   const char *(*invalid_binary_op) (int op, tree type1, tree type2);
 644
 645   /* Return the class for a secondary reload, and fill in extra information.  */
 646   enum reg_class (*secondary_reload) (bool, rtx, enum reg_class,
 647                                       enum machine_mode,
 648                                       struct secondary_reload_info *);
 649
 650   /* Functions specific to the C++ frontend.  */
 651   struct cxx {
 652     /* Return the integer type used for guard variables.  */
 653     tree (*guard_type) (void);
 654     /* Return true if only the low bit of the guard should be tested.  */
 655     bool (*guard_mask_bit) (void);
 656     /* Returns the size of the array cookie for an array of type.  */
 657     tree (*get_cookie_size) (tree);
 658     /* Returns true if the element size should be stored in the
 659        array cookie.  */
 660     bool (*cookie_has_size) (void);
 661     /* Allows backends to perform additional processing when
 662        deciding if a class should be exported or imported.  */
 663     int (*import_export_class) (tree, int);
 664     /* Returns true if constructors and destructors return "this".  */
 665     bool (*cdtor_returns_this) (void);
 666     /* Returns true if the key method for a class can be an inline
 667        function, so long as it is not declared inline in the class
 668        itself.  Returning true is the behavior required by the Itanium
 669        C++ ABI.  */
 670     bool (*key_method_may_be_inline) (void);
 671     /* DECL is a virtual table, virtual table table, typeinfo object,
 672        or other similar implicit class data object that will be
 673        emitted with external linkage in this translation unit.  No ELF
 674        visibility has been explicitly specified.  If the target needs
 675        to specify a visibility other than that of the containing class,
 676        use this hook to set DECL_VISIBILITY and
 677        DECL_VISIBILITY_SPECIFIED.  */
 678     void (*determine_class_data_visibility) (tree decl);
 679     /* Returns true (the default) if virtual tables and other
 680        similar implicit class data objects are always COMDAT if they
 681        have external linkage.  If this hook returns false, then
 682        class data for classes whose virtual table will be emitted in
 683        only one translation unit will not be COMDAT.  */
 684     bool (*class_data_always_comdat) (void);
 685     /* Returns true if __aeabi_atexit should be used to register static
 686        destructors.  */
 687     bool (*use_aeabi_atexit) (void);
 688     /* TYPE is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that
 689        has just been defined.  Use this hook to make adjustments to the
 690        class  (eg, tweak visibility or perform any other required
 691        target modifications).  */
 692     void (*adjust_class_at_definition) (tree type);
 693   } cxx;
 694
 695   /* True if unwinding tables should be generated by default.  */
 696   bool unwind_tables_default;
 697
 698   /* Leave the boolean fields at the end.  */
 699
 700   /* True if arbitrary sections are supported.  */
 701   bool have_named_sections;
 702
 703   /* True if "native" constructors and destructors are supported,
 704      false if we're using collect2 for the job.  */
 705   bool have_ctors_dtors;
 706
 707   /* True if thread-local storage is supported.  */
 708   bool have_tls;
 709
 710   /* True if a small readonly data section is supported.  */
 711   bool have_srodata_section;
 712
 713   /* True if EH frame info sections should be zero-terminated.  */
 714   bool terminate_dw2_eh_frame_info;
 715
 716   /* True if #NO_APP should be emitted at the beginning of
 717      assembly output.  */
 718   bool file_start_app_off;
 719
 720   /* True if output_file_directive should be called for main_input_filename
 721      at the beginning of assembly output.  */
 722   bool file_start_file_directive;
 723
 724   /* True if #pragma redefine_extname is to be supported.  */
 725   bool handle_pragma_redefine_extname;
 726
 727   /* True if #pragma extern_prefix is to be supported.  */
 728   bool handle_pragma_extern_prefix;
 729
 730   /* True if the target is allowed to reorder memory accesses unless
 731      synchronization is explicitly requested.  */
 732   bool relaxed_ordering;
 733
 734   /* Returns true if we should generate exception tables for use with the
 735      ARM EABI.  The effects the encoding of function exception specifications.
 736    */
 737   bool arm_eabi_unwinder;
 738
 739   /* Leave the boolean fields at the end.  */
 740 };
 741
 742 extern struct gcc_target targetm;
 743
 744 #endif /* GCC_TARGET_H */