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