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     /* Output code that will emit a label to divide up the exception
 106        table.  */
 107     void (* except_table_label) (FILE *);
 108
 109     /* Emit any directives required to unwind this instruction.  */
 110     void (* unwind_emit) (FILE *, rtx);
 111
 112     /* Output an internal label.  */
 113     void (* internal_label) (FILE *, const char *, unsigned long);
 114
 115     /* Emit a ttype table reference to a typeinfo object.  */
 116     bool (* ttype) (rtx);
 117
 118     /* Emit an assembler directive to set visibility for the symbol
 119        associated with the tree decl.  */
 120     void (* visibility) (tree, int);
 121
 122     /* Output the assembler code for entry to a function.  */
 123     void (* function_prologue) (FILE *, HOST_WIDE_INT);
 124
 125     /* Output the assembler code for end of prologue.  */
 126     void (* function_end_prologue) (FILE *);
 127
 128     /* Output the assembler code for start of epilogue.  */
 129     void (* function_begin_epilogue) (FILE *);
 130
 131     /* Output the assembler code for function exit.  */
 132     void (* function_epilogue) (FILE *, HOST_WIDE_INT);
 133
 134     /* Initialize target-specific sections.  */
 135     void (* init_sections) (void);
 136
 137     /* Tell assembler to change to section NAME with attributes FLAGS.
 138        If DECL is non-NULL, it is the VAR_DECL or FUNCTION_DECL with
 139        which this section is associated.  */
 140     void (* named_section) (const char *name, unsigned int flags, tree decl);
 141
 142     /* Return a section for EXP.  It may be a DECL or a constant.  RELOC
 143        is nonzero if runtime relocations must be applied; bit 1 will be
 144        set if the runtime relocations require non-local name resolution.
 145        ALIGN is the required alignment of the data.  */
 146     section *(* select_section) (tree, int, unsigned HOST_WIDE_INT);
 147
 148     /* Return a section for X.  MODE is X's mode and ALIGN is its
 149        alignment in bits.  */
 150     section *(* select_rtx_section) (enum machine_mode, rtx,
 151                                      unsigned HOST_WIDE_INT);
 152
 153     /* Select a unique section name for DECL.  RELOC is the same as
 154        for SELECT_SECTION.  */
 155     void (* unique_section) (tree, int);
 156
 157     /* Return the readonly data section associated with function DECL.  */
 158     section *(* function_rodata_section) (tree);
 159
 160     /* Output a constructor for a symbol with a given priority.  */
 161     void (* constructor) (rtx, int);
 162
 163     /* Output a destructor for a symbol with a given priority.  */
 164     void (* destructor) (rtx, int);
 165
 166     /* Output the assembler code for a thunk function.  THUNK_DECL is the
 167        declaration for the thunk function itself, FUNCTION is the decl for
 168        the target function.  DELTA is an immediate constant offset to be
 169        added to THIS.  If VCALL_OFFSET is nonzero, the word at
 170        *(*this + vcall_offset) should be added to THIS.  */
 171     void (* output_mi_thunk) (FILE *file, tree thunk_decl,
 172                               HOST_WIDE_INT delta, HOST_WIDE_INT vcall_offset,
 173                               tree function_decl);
 174
 175     /* Determine whether output_mi_thunk would succeed.  */
 176     /* ??? Ideally, this hook would not exist, and success or failure
 177        would be returned from output_mi_thunk directly.  But there's
 178        too much undo-able setup involved in invoking output_mi_thunk.
 179        Could be fixed by making output_mi_thunk emit rtl instead of
 180        text to the output file.  */
 181     bool (* can_output_mi_thunk) (tree thunk_decl, HOST_WIDE_INT delta,
 182                                   HOST_WIDE_INT vcall_offset,
 183                                   tree function_decl);
 184
 185     /* Output any boilerplate text needed at the beginning of a
 186        translation unit.  */
 187     void (*file_start) (void);
 188
 189     /* Output any boilerplate text needed at the end of a
 190        translation unit.  */
 191     void (*file_end) (void);
 192
 193     /* Output an assembler pseudo-op to declare a library function name
 194        external.  */
 195     void (*external_libcall) (rtx);
 196
 197      /* Output an assembler directive to mark decl live. This instructs
 198         linker to not dead code strip this symbol.  */
 199     void (*mark_decl_preserved) (const char *);
 200
 201     /* Output the definition of a section anchor.  */
 202     void (*output_anchor) (rtx);
 203
 204     /* Output a DTP-relative reference to a TLS symbol.  */
 205     void (*output_dwarf_dtprel) (FILE *file, int size, rtx x);
 206
 207   } asm_out;
 208
 209   /* Functions relating to instruction scheduling.  */
 210   struct sched
 211   {
 212     /* Given the current cost, COST, of an insn, INSN, calculate and
 213        return a new cost based on its relationship to DEP_INSN through
 214        the dependence LINK.  The default is to make no adjustment.  */
 215     int (* adjust_cost) (rtx insn, rtx link, rtx def_insn, int cost);
 216
 217     /* Adjust the priority of an insn as you see fit.  Returns the new
 218        priority.  */
 219     int (* adjust_priority) (rtx, int);
 220
 221     /* Function which returns the maximum number of insns that can be
 222        scheduled in the same machine cycle.  This must be constant
 223        over an entire compilation.  The default is 1.  */
 224     int (* issue_rate) (void);
 225
 226     /* Calculate how much this insn affects how many more insns we
 227        can emit this cycle.  Default is they all cost the same.  */
 228     int (* variable_issue) (FILE *, int, rtx, int);
 229
 230     /* Initialize machine-dependent scheduling code.  */
 231     void (* md_init) (FILE *, int, int);
 232
 233     /* Finalize machine-dependent scheduling code.  */
 234     void (* md_finish) (FILE *, int);
 235
 236     /* Initialize machine-dependent function while scheduling code.  */
 237     void (* md_init_global) (FILE *, int, int);
 238
 239     /* Finalize machine-dependent function wide scheduling code.  */
 240     void (* md_finish_global) (FILE *, int);
 241
 242     /* Reorder insns in a machine-dependent fashion, in two different
 243        places.  Default does nothing.  */
 244     int (* reorder) (FILE *, int, rtx *, int *, int);
 245     int (* reorder2) (FILE *, int, rtx *, int *, int);
 246
 247     /* The following member value is a pointer to a function called
 248        after evaluation forward dependencies of insns in chain given
 249        by two parameter values (head and tail correspondingly).  */
 250     void (* dependencies_evaluation_hook) (rtx, rtx);
 251
 252     /* The values of the following four members are pointers to
 253        functions used to simplify the automaton descriptions.
 254        dfa_pre_cycle_insn and dfa_post_cycle_insn give functions
 255        returning insns which are used to change the pipeline hazard
 256        recognizer state when the new simulated processor cycle
 257        correspondingly starts and finishes.  The function defined by
 258        init_dfa_pre_cycle_insn and init_dfa_post_cycle_insn are used
 259        to initialize the corresponding insns.  The default values of
 260        the members result in not changing the automaton state when
 261        the new simulated processor cycle correspondingly starts and
 262        finishes.  */
 263     void (* init_dfa_pre_cycle_insn) (void);
 264     rtx (* dfa_pre_cycle_insn) (void);
 265     void (* init_dfa_post_cycle_insn) (void);
 266     rtx (* dfa_post_cycle_insn) (void);
 267
 268     /* The following member value is a pointer to a function returning value
 269        which defines how many insns in queue `ready' will we try for
 270        multi-pass scheduling.  If the member value is nonzero and the
 271        function returns positive value, the DFA based scheduler will make
 272        multi-pass scheduling for the first cycle.  In other words, we will
 273        try to choose ready insn which permits to start maximum number of
 274        insns on the same cycle.  */
 275     int (* first_cycle_multipass_dfa_lookahead) (void);
 276
 277     /* The following member value is pointer to a function controlling
 278        what insns from the ready insn queue will be considered for the
 279        multipass insn scheduling.  If the hook returns zero for insn
 280        passed as the parameter, the insn will be not chosen to be
 281        issued.  */
 282     int (* first_cycle_multipass_dfa_lookahead_guard) (rtx);
 283
 284     /* The following member value is pointer to a function called by
 285        the insn scheduler before issuing insn passed as the third
 286        parameter on given cycle.  If the hook returns nonzero, the
 287        insn is not issued on given processors cycle.  Instead of that,
 288        the processor cycle is advanced.  If the value passed through
 289        the last parameter is zero, the insn ready queue is not sorted
 290        on the new cycle start as usually.  The first parameter passes
 291        file for debugging output.  The second one passes the scheduler
 292        verbose level of the debugging output.  The forth and the fifth
 293        parameter values are correspondingly processor cycle on which
 294        the previous insn has been issued and the current processor
 295        cycle.  */
 296     int (* dfa_new_cycle) (FILE *, int, rtx, int, int, int *);
 297
 298     /* The following member value is a pointer to a function called
 299        by the insn scheduler.  It should return true if there exists a
 300        dependence which is considered costly by the target, between
 301        the insn passed as the first parameter, and the insn passed as
 302        the second parameter.  The third parameter is the INSN_DEPEND
 303        link that represents the dependence between the two insns.  The
 304        fourth argument is the cost of the dependence as estimated by
 305        the scheduler.  The last argument is the distance in cycles
 306        between the already scheduled insn (first parameter) and the
 307        the second insn (second parameter).  */
 308     bool (* is_costly_dependence) (rtx, rtx, rtx, int, int);
 309   } sched;
 310
 311   /* Functions relating to vectorization.  */
 312   struct vectorize
 313   {
 314     /* The following member value is a pointer to a function called
 315        by the vectorizer, and return the decl of the target builtin
 316        function.  */
 317     tree (* builtin_mask_for_load) (void);
 318   } vectorize;
 319
 320   /* The initial value of target_flags.  */
 321   int default_target_flags;
 322
 323   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
 324      passed to the switch; it is NULL if no argument was.  VALUE is the
 325      value of ARG if CODE specifies a UInteger option, otherwise it is
 326      1 if the positive form of the switch was used and 0 if the negative
 327      form was.  Return true if the switch was valid.  */
 328   bool (* handle_option) (size_t code, const char *arg, int value);
 329
 330   /* Return machine mode for filter value.  */
 331   enum machine_mode (* eh_return_filter_mode) (void);
 332
 333   /* Given two decls, merge their attributes and return the result.  */
 334   tree (* merge_decl_attributes) (tree, tree);
 335
 336   /* Given two types, merge their attributes and return the result.  */
 337   tree (* merge_type_attributes) (tree, tree);
 338
 339   /* Table of machine attributes and functions to handle them.
 340      Ignored if NULL.  */
 341   const struct attribute_spec *attribute_table;
 342
 343   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 344      one if they are compatible and two if they are nearly compatible
 345      (which causes a warning to be generated).  */
 346   int (* comp_type_attributes) (tree type1, tree type2);
 347
 348   /* Assign default attributes to the newly defined TYPE.  */
 349   void (* set_default_type_attributes) (tree type);
 350
 351   /* Insert attributes on the newly created DECL.  */
 352   void (* insert_attributes) (tree decl, tree *attributes);
 353
 354   /* Return true if FNDECL (which has at least one machine attribute)
 355      can be inlined despite its machine attributes, false otherwise.  */
 356   bool (* function_attribute_inlinable_p) (tree fndecl);
 357
 358   /* Return true if bitfields in RECORD_TYPE should follow the
 359      Microsoft Visual C++ bitfield layout rules.  */
 360   bool (* ms_bitfield_layout_p) (tree record_type);
 361
 362   /* True if the target supports decimal floating point.  */
 363   bool (* decimal_float_supported_p) (void);
 364
 365   /* Return true if anonymous bitfields affect structure alignment.  */
 366   bool (* align_anon_bitfield) (void);
 367
 368   /* Set up target-specific built-in functions.  */
 369   void (* init_builtins) (void);
 370
 371   /* Expand a target-specific builtin.  */
 372   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 373                           enum machine_mode mode, int ignore);
 374
 375   /* Expand a target-specific library builtin.  */
 376   rtx (* expand_library_builtin) (tree exp, rtx target, rtx subtarget,
 377                           enum machine_mode mode, int ignore);
 378
 379   /* Select a replacement for a target-specific builtin.  This is done
 380      *before* regular type checking, and so allows the target to implement
 381      a crude form of function overloading.  The result is a complete
 382      expression that implements the operation.  */
 383   tree (*resolve_overloaded_builtin) (tree decl, tree params);
 384
 385   /* Fold a target-specific builtin.  */
 386   tree (* fold_builtin) (tree fndecl, tree arglist, bool ignore);
 387
 388   /* For a vendor-specific fundamental TYPE, return a pointer to
 389      a statically-allocated string containing the C++ mangling for
 390      TYPE.  In all other cases, return NULL.  */
 391   const char * (* mangle_fundamental_type) (tree type);
 392
 393   /* Make any adjustments to libfunc names needed for this target.  */
 394   void (* init_libfuncs) (void);
 395
 396   /* Given a decl, a section name, and whether the decl initializer
 397      has relocs, choose attributes for the section.  */
 398   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 399   unsigned int (* section_type_flags) (tree, const char *, int);
 400
 401   /* True if new jumps cannot be created, to replace existing ones or
 402      not, at the current point in the compilation.  */
 403   bool (* cannot_modify_jumps_p) (void);
 404
 405   /* Return a register class for which branch target register
 406      optimizations should be applied.  */
 407   int (* branch_target_register_class) (void);
 408
 409   /* Return true if branch target register optimizations should include
 410      callee-saved registers that are not already live during the current
 411      function.  AFTER_PE_GEN is true if prologues and epilogues have
 412      already been generated.  */
 413   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 414
 415   /* True if the constant X cannot be placed in the constant pool.  */
 416   bool (* cannot_force_const_mem) (rtx);
 417
 418   /* True if the insn X cannot be duplicated.  */
 419   bool (* cannot_copy_insn_p) (rtx);
 420
 421   /* True if X is considered to be commutative.  */
 422   bool (* commutative_p) (rtx, int);
 423
 424   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 425   rtx (* delegitimize_address) (rtx);
 426
 427   /* True if the given constant can be put into an object_block.  */
 428   bool (* use_blocks_for_constant_p) (enum machine_mode, rtx);
 429
 430   /* The minimum and maximum byte offsets for anchored addresses.  */
 431   HOST_WIDE_INT min_anchor_offset;
 432   HOST_WIDE_INT max_anchor_offset;
 433
 434   /* True if section anchors can be used to access the given symbol.  */
 435   bool (* use_anchors_for_symbol_p) (rtx);
 436
 437   /* True if it is OK to do sibling call optimization for the specified
 438      call expression EXP.  DECL will be the called function, or NULL if
 439      this is an indirect call.  */
 440   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 441
 442   /* True if EXP should be placed in a "small data" section.  */
 443   bool (* in_small_data_p) (tree);
 444
 445   /* True if EXP names an object for which name resolution must resolve
 446      to the current module.  */
 447   bool (* binds_local_p) (tree);
 448
 449   /* Do something target-specific to record properties of the DECL into
 450      the associated SYMBOL_REF.  */
 451   void (* encode_section_info) (tree, rtx, int);
 452
 453   /* Undo the effects of encode_section_info on the symbol string.  */
 454   const char * (* strip_name_encoding) (const char *);
 455
 456   /* If shift optabs for MODE are known to always truncate the shift count,
 457      return the mask that they apply.  Return 0 otherwise.  */
 458   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
 459
 460   /* Return the number of divisions in the given MODE that should be present,
 461      so that it is profitable to turn the division into a multiplication by
 462      the reciprocal.  */
 463   unsigned int (* min_divisions_for_recip_mul) (enum machine_mode mode);
 464
 465   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 466   bool (* valid_pointer_mode) (enum machine_mode mode);
 467
 468   /* True if MODE is valid for the target.  By "valid", we mean able to
 469      be manipulated in non-trivial ways.  In particular, this means all
 470      the arithmetic is supported.  */
 471   bool (* scalar_mode_supported_p) (enum machine_mode mode);
 472
 473   /* Similarly for vector modes.  "Supported" here is less strict.  At
 474      least some operations are supported; need to check optabs or builtins
 475      for further details.  */
 476   bool (* vector_mode_supported_p) (enum machine_mode mode);
 477
 478   /* True if a vector is opaque.  */
 479   bool (* vector_opaque_p) (tree);
 480
 481   /* Compute a (partial) cost for rtx X.  Return true if the complete
 482      cost has been computed, and false if subexpressions should be
 483      scanned.  In either case, *TOTAL contains the cost result.  */
 484   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 485      not necessarily defined at this point.  */
 486   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 487
 488   /* Compute the cost of X, used as an address.  Never called with
 489      invalid addresses.  */
 490   int (* address_cost) (rtx x);
 491
 492   /* Return where to allocate pseudo for a given hard register initial
 493      value.  */
 494   rtx (* allocate_initial_value) (rtx x);
 495
 496   /* Given a register, this hook should return a parallel of registers
 497      to represent where to find the register pieces.  Define this hook
 498      if the register and its mode are represented in Dwarf in
 499      non-contiguous locations, or if the register should be
 500      represented in more than one register in Dwarf.  Otherwise, this
 501      hook should return NULL_RTX.  */
 502   rtx (* dwarf_register_span) (rtx);
 503
 504   /* Fetch the fixed register(s) which hold condition codes, for
 505      targets where it makes sense to look for duplicate assignments to
 506      the condition codes.  This should return true if there is such a
 507      register, false otherwise.  The arguments should be set to the
 508      fixed register numbers.  Up to two condition code registers are
 509      supported.  If there is only one for this target, the int pointed
 510      at by the second argument should be set to -1.  */
 511   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 512
 513   /* If two condition code modes are compatible, return a condition
 514      code mode which is compatible with both, such that a comparison
 515      done in the returned mode will work for both of the original
 516      modes.  If the condition code modes are not compatible, return
 517      VOIDmode.  */
 518   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 519                                              enum machine_mode);
 520
 521   /* Do machine-dependent code transformations.  Called just before
 522      delayed-branch scheduling.  */
 523   void (* machine_dependent_reorg) (void);
 524
 525   /* Create the __builtin_va_list type.  */
 526   tree (* build_builtin_va_list) (void);
 527
 528   /* Gimplifies a VA_ARG_EXPR.  */
 529   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 530                                  tree *post_p);
 531
 532   /* Validity-checking routines for PCH files, target-specific.
 533      get_pch_validity returns a pointer to the data to be stored,
 534      and stores the size in its argument.  pch_valid_p gets the same
 535      information back and returns NULL if the PCH is valid,
 536      or an error message if not.
 537   */
 538   void * (* get_pch_validity) (size_t *);
 539   const char * (* pch_valid_p) (const void *, size_t);
 540
 541   /* If nonnull, this function checks whether a PCH file with the
 542      given set of target flags can be used.  It returns NULL if so,
 543      otherwise it returns an error message.  */
 544   const char *(*check_pch_target_flags) (int);
 545
 546   /* True if the compiler should give an enum type only as many
 547      bytes as it takes to represent the range of possible values of
 548      that type.  */
 549   bool (* default_short_enums) (void);
 550
 551   /* This target hook returns an rtx that is used to store the address
 552      of the current frame into the built-in setjmp buffer.  */
 553   rtx (* builtin_setjmp_frame_value) (void);
 554
 555   /* This target hook should add STRING_CST trees for any hard regs
 556      the port wishes to automatically clobber for an asm.  */
 557   tree (* md_asm_clobbers) (tree, tree, tree);
 558
 559   /* This target hook allows the backend to specify a calling convention
 560      in the debug information.  This function actually returns an
 561      enum dwarf_calling_convention, but because of forward declarations
 562      and not wanting to include dwarf2.h everywhere target.h is included
 563      the function is being declared as an int.  */
 564   int (* dwarf_calling_convention) (tree);
 565
 566   /* This target hook allows the backend to emit frame-related insns that
 567      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
 568      engine will invoke it on insns of the form
 569        (set (reg) (unspec [...] UNSPEC_INDEX))
 570      and
 571        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
 572      to let the backend emit the call frame instructions.  */
 573   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
 574
 575   /* Perform architecture specific checking of statements gimplified
 576      from VA_ARG_EXPR.  LHS is left hand side of MODIFY_EXPR, RHS
 577      is right hand side.  Returns true if the statements doesn't need
 578      to be checked for va_list references.  */
 579   bool (* stdarg_optimize_hook) (struct stdarg_info *ai, tree lhs, tree rhs);
 580
 581   /* This target hook allows the operating system to override the DECL
 582      that represents the external variable that contains the stack
 583      protection guard variable.  The type of this DECL is ptr_type_node.  */
 584   tree (* stack_protect_guard) (void);
 585
 586   /* This target hook allows the operating system to override the CALL_EXPR
 587      that is invoked when a check vs the guard variable fails.  */
 588   tree (* stack_protect_fail) (void);
 589
 590   /* Returns NULL if target supports the insn within a doloop block,
 591      otherwise it returns an error message.  */
 592   const char * (*invalid_within_doloop) (rtx);
 593
 594   /* DECL is a variable or function with __attribute__((dllimport))
 595      specified.  Use this hook if the target needs to add extra validation
 596      checks to  handle_dll_attribute ().  */
 597   bool (* valid_dllimport_attribute_p) (tree decl);
 598
 599   /* Functions relating to calls - argument passing, returns, etc.  */
 600   struct calls {
 601     bool (*promote_function_args) (tree fntype);
 602     bool (*promote_function_return) (tree fntype);
 603     bool (*promote_prototypes) (tree fntype);
 604     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 605     bool (*return_in_memory) (tree type, tree fndecl);
 606     bool (*return_in_msb) (tree type);
 607
 608     /* Return true if a parameter must be passed by reference.  TYPE may
 609        be null if this is a libcall.  CA may be null if this query is
 610        from __builtin_va_arg.  */
 611     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 612                                tree type, bool named_arg);
 613
 614     rtx (*expand_builtin_saveregs) (void);
 615     /* Returns pretend_argument_size.  */
 616     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 617                                     tree type, int *pretend_arg_size,
 618                                     int second_time);
 619     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 620     /* Returns true if we should use
 621        targetm.calls.setup_incoming_varargs() and/or
 622        targetm.calls.strict_argument_naming().  */
 623     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 624
 625     /* Given a complex type T, return true if a parameter of type T
 626        should be passed as two scalars.  */
 627     bool (* split_complex_arg) (tree type);
 628
 629     /* Return true if type T, mode MODE, may not be passed in registers,
 630        but must be passed on the stack.  */
 631     /* ??? This predicate should be applied strictly after pass-by-reference.
 632        Need audit to verify that this is the case.  */
 633     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 634
 635     /* Return true if type TYPE, mode MODE, which is passed by reference,
 636        should have the object copy generated by the callee rather than
 637        the caller.  It is never called for TYPE requiring constructors.  */
 638     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 639                             tree type, bool named);
 640
 641     /* Return zero for arguments passed entirely on the stack or entirely
 642        in registers.  If passed in both, return the number of bytes passed
 643        in registers; the balance is therefore passed on the stack.  */
 644     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 645                                tree type, bool named);
 646
 647     /* Return the diagnostic message string if function without a prototype
 648        is not allowed for this 'val' argument; NULL otherwise. */
 649     const char *(*invalid_arg_for_unprototyped_fn) (tree typelist,
 650                                                     tree funcdecl, tree val);
 651
 652     /* Return an rtx for the return value location of the function
 653        specified by FN_DECL_OR_TYPE with a return type of RET_TYPE.  */
 654     rtx (*function_value) (tree ret_type, tree fn_decl_or_type,
 655                            bool outgoing);
 656
 657     /* Return an rtx for the argument pointer incoming to the
 658        current function.  */
 659     rtx (*internal_arg_pointer) (void);
 660   } calls;
 661
 662   /* Return the diagnostic message string if conversion from FROMTYPE
 663      to TOTYPE is not allowed, NULL otherwise.  */
 664   const char *(*invalid_conversion) (tree fromtype, tree totype);
 665
 666   /* Return the diagnostic message string if the unary operation OP is
 667      not permitted on TYPE, NULL otherwise.  */
 668   const char *(*invalid_unary_op) (int op, tree type);
 669
 670   /* Return the diagnostic message string if the binary operation OP
 671      is not permitted on TYPE1 and TYPE2, NULL otherwise.  */
 672   const char *(*invalid_binary_op) (int op, tree type1, tree type2);
 673
 674   /* Return the class for a secondary reload, and fill in extra information.  */
 675   enum reg_class (*secondary_reload) (bool, rtx, enum reg_class,
 676                                       enum machine_mode,
 677                                       struct secondary_reload_info *);
 678
 679   /* Functions specific to the C++ frontend.  */
 680   struct cxx {
 681     /* Return the integer type used for guard variables.  */
 682     tree (*guard_type) (void);
 683     /* Return true if only the low bit of the guard should be tested.  */
 684     bool (*guard_mask_bit) (void);
 685     /* Returns the size of the array cookie for an array of type.  */
 686     tree (*get_cookie_size) (tree);
 687     /* Returns true if the element size should be stored in the
 688        array cookie.  */
 689     bool (*cookie_has_size) (void);
 690     /* Allows backends to perform additional processing when
 691        deciding if a class should be exported or imported.  */
 692     int (*import_export_class) (tree, int);
 693     /* Returns true if constructors and destructors return "this".  */
 694     bool (*cdtor_returns_this) (void);
 695     /* Returns true if the key method for a class can be an inline
 696        function, so long as it is not declared inline in the class
 697        itself.  Returning true is the behavior required by the Itanium
 698        C++ ABI.  */
 699     bool (*key_method_may_be_inline) (void);
 700     /* DECL is a virtual table, virtual table table, typeinfo object,
 701        or other similar implicit class data object that will be
 702        emitted with external linkage in this translation unit.  No ELF
 703        visibility has been explicitly specified.  If the target needs
 704        to specify a visibility other than that of the containing class,
 705        use this hook to set DECL_VISIBILITY and
 706        DECL_VISIBILITY_SPECIFIED.  */
 707     void (*determine_class_data_visibility) (tree decl);
 708     /* Returns true (the default) if virtual tables and other
 709        similar implicit class data objects are always COMDAT if they
 710        have external linkage.  If this hook returns false, then
 711        class data for classes whose virtual table will be emitted in
 712        only one translation unit will not be COMDAT.  */
 713     bool (*class_data_always_comdat) (void);
 714     /* Returns true if __aeabi_atexit should be used to register static
 715        destructors.  */
 716     bool (*use_aeabi_atexit) (void);
 717     /* TYPE is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that
 718        has just been defined.  Use this hook to make adjustments to the
 719        class  (eg, tweak visibility or perform any other required
 720        target modifications).  */
 721     void (*adjust_class_at_definition) (tree type);
 722   } cxx;
 723
 724   /* For targets that need to mark extra registers as live on entry to
 725      the function, they should define this target hook and set their
 726      bits in the bitmap passed in. */
 727   void (*live_on_entry) (bitmap);
 728
 729   /* True if unwinding tables should be generated by default.  */
 730   bool unwind_tables_default;
 731
 732   /* Leave the boolean fields at the end.  */
 733
 734   /* True if arbitrary sections are supported.  */
 735   bool have_named_sections;
 736
 737   /* True if we can create zeroed data by switching to a BSS section
 738      and then using ASM_OUTPUT_SKIP to allocate the space.  */
 739   bool have_switchable_bss_sections;
 740
 741   /* True if "native" constructors and destructors are supported,
 742      false if we're using collect2 for the job.  */
 743   bool have_ctors_dtors;
 744
 745   /* True if thread-local storage is supported.  */
 746   bool have_tls;
 747
 748   /* True if a small readonly data section is supported.  */
 749   bool have_srodata_section;
 750
 751   /* True if EH frame info sections should be zero-terminated.  */
 752   bool terminate_dw2_eh_frame_info;
 753
 754   /* True if #NO_APP should be emitted at the beginning of
 755      assembly output.  */
 756   bool file_start_app_off;
 757
 758   /* True if output_file_directive should be called for main_input_filename
 759      at the beginning of assembly output.  */
 760   bool file_start_file_directive;
 761
 762   /* True if #pragma redefine_extname is to be supported.  */
 763   bool handle_pragma_redefine_extname;
 764
 765   /* True if #pragma extern_prefix is to be supported.  */
 766   bool handle_pragma_extern_prefix;
 767
 768   /* True if the target is allowed to reorder memory accesses unless
 769      synchronization is explicitly requested.  */
 770   bool relaxed_ordering;
 771
 772   /* Returns true if we should generate exception tables for use with the
 773      ARM EABI.  The effects the encoding of function exception specifications.
 774    */
 775   bool arm_eabi_unwinder;
 776
 777   /* Leave the boolean fields at the end.  */
 778 };
 779
 780 extern struct gcc_target targetm;
 781
 782 #endif /* GCC_TARGET_H */