gcc/target.h

   1 /* Data structure definitions for a generic GCC target.
   2    Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007
   3    Free Software Foundation, Inc.
   4
   5 This program is free software; you can redistribute it and/or modify it
   6 under the terms of the GNU General Public License as published by the
   7 Free Software Foundation; either version 2, or (at your option) any
   8 later version.
   9
  10 This program is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this program; if not, write to the Free Software
  17 Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18
  19  In other words, you are welcome to use, share and improve this program.
  20  You are forbidden to forbid anyone else to use, share and improve
  21  what you give them.   Help stamp out software-hoarding!  */
  22
  23 /* This file contains a data structure that describes a GCC target.
  24    At present it is incomplete, but in future it should grow to
  25    contain most or all target machine and target O/S specific
  26    information.
  27
  28    This structure has its initializer declared in target-def.h in the
  29    form of large macro TARGET_INITIALIZER that expands to many smaller
  30    macros.
  31
  32    The smaller macros each initialize one component of the structure,
  33    and each has a default.  Each target should have a file that
  34    includes target.h and target-def.h, and overrides any inappropriate
  35    defaults by undefining the relevant macro and defining a suitable
  36    replacement.  That file should then contain the definition of
  37    "targetm" like so:
  38
  39    struct gcc_target targetm = TARGET_INITIALIZER;
  40
  41    Doing things this way allows us to bring together everything that
  42    defines a GCC target.  By supplying a default that is appropriate
  43    to most targets, we can easily add new items without needing to
  44    edit dozens of target configuration files.  It should also allow us
  45    to gradually reduce the amount of conditional compilation that is
  46    scattered throughout GCC.  */
  47
  48 #ifndef GCC_TARGET_H
  49 #define GCC_TARGET_H
  50
  51 #include "tm.h"
  52 #include "insn-modes.h"
  53
  54 struct stdarg_info;
  55 struct spec_info_def;
  56
  57 /* The struct used by the secondary_reload target hook.  */
  58 typedef struct secondary_reload_info
  59 {
  60   /* icode is actually an enum insn_code, but we don't want to force every
  61      file that includes target.h to include optabs.h .  */
  62   int icode;
  63   int extra_cost; /* Cost for using (a) scratch register(s) to be taken
  64                      into account by copy_cost.  */
  65   /* The next two members are for the use of the backward
  66      compatibility hook.  */
  67   struct secondary_reload_info *prev_sri;
  68   int t_icode; /* Actually an enum insn_code - see above.  */
  69 } secondary_reload_info;
  70
  71
  72 struct gcc_target
  73 {
  74   /* Functions that output assembler for the target.  */
  75   struct asm_out
  76   {
  77     /* Opening and closing parentheses for asm expression grouping.  */
  78     const char *open_paren, *close_paren;
  79
  80     /* Assembler instructions for creating various kinds of integer object.  */
  81     const char *byte_op;
  82     struct asm_int_op
  83     {
  84       const char *hi;
  85       const char *si;
  86       const char *di;
  87       const char *ti;
  88     } aligned_op, unaligned_op;
  89
  90     /* Try to output the assembler code for an integer object whose
  91        value is given by X.  SIZE is the size of the object in bytes and
  92        ALIGNED_P indicates whether it is aligned.  Return true if
  93        successful.  Only handles cases for which BYTE_OP, ALIGNED_OP
  94        and UNALIGNED_OP are NULL.  */
  95     bool (* integer) (rtx x, unsigned int size, int aligned_p);
  96
  97     /* Output code that will globalize a label.  */
  98     void (* globalize_label) (FILE *, const char *);
  99
 100     /* Output code that will emit a label for unwind info, if this
 101        target requires such labels.  Second argument is the decl the
 102        unwind info is associated with, third is a boolean: true if
 103        this is for exception handling, fourth is a boolean: true if
 104        this is only a placeholder for an omitted FDE.  */
 105     void (* unwind_label) (FILE *, tree, int, int);
 106
 107     /* Output code that will emit a label to divide up the exception
 108        table.  */
 109     void (* except_table_label) (FILE *);
 110
 111     /* Emit any directives required to unwind this instruction.  */
 112     void (* unwind_emit) (FILE *, rtx);
 113
 114     /* Output an internal label.  */
 115     void (* internal_label) (FILE *, const char *, unsigned long);
 116
 117     /* Emit a ttype table reference to a typeinfo object.  */
 118     bool (* ttype) (rtx);
 119
 120     /* Emit an assembler directive to set visibility for the symbol
 121        associated with the tree decl.  */
 122     void (* visibility) (tree, int);
 123
 124     /* Output the assembler code for entry to a function.  */
 125     void (* function_prologue) (FILE *, HOST_WIDE_INT);
 126
 127     /* Output the assembler code for end of prologue.  */
 128     void (* function_end_prologue) (FILE *);
 129
 130     /* Output the assembler code for start of epilogue.  */
 131     void (* function_begin_epilogue) (FILE *);
 132
 133     /* Output the assembler code for function exit.  */
 134     void (* function_epilogue) (FILE *, HOST_WIDE_INT);
 135
 136     /* Initialize target-specific sections.  */
 137     void (* init_sections) (void);
 138
 139     /* Tell assembler to change to section NAME with attributes FLAGS.
 140        If DECL is non-NULL, it is the VAR_DECL or FUNCTION_DECL with
 141        which this section is associated.  */
 142     void (* named_section) (const char *name, unsigned int flags, tree decl);
 143
 144     /* Return a mask describing how relocations should be treated when
 145        selecting sections.  Bit 1 should be set if global relocations
 146        should be placed in a read-write section; bit 0 should be set if
 147        local relocations should be placed in a read-write section.  */
 148     int (*reloc_rw_mask) (void);
 149
 150     /* Return a section for EXP.  It may be a DECL or a constant.  RELOC
 151        is nonzero if runtime relocations must be applied; bit 1 will be
 152        set if the runtime relocations require non-local name resolution.
 153        ALIGN is the required alignment of the data.  */
 154     section *(* select_section) (tree, int, unsigned HOST_WIDE_INT);
 155
 156     /* Return a section for X.  MODE is X's mode and ALIGN is its
 157        alignment in bits.  */
 158     section *(* select_rtx_section) (enum machine_mode, rtx,
 159                                      unsigned HOST_WIDE_INT);
 160
 161     /* Select a unique section name for DECL.  RELOC is the same as
 162        for SELECT_SECTION.  */
 163     void (* unique_section) (tree, int);
 164
 165     /* Return the readonly data section associated with function DECL.  */
 166     section *(* function_rodata_section) (tree);
 167
 168     /* Output a constructor for a symbol with a given priority.  */
 169     void (* constructor) (rtx, int);
 170
 171     /* Output a destructor for a symbol with a given priority.  */
 172     void (* destructor) (rtx, int);
 173
 174     /* Output the assembler code for a thunk function.  THUNK_DECL is the
 175        declaration for the thunk function itself, FUNCTION is the decl for
 176        the target function.  DELTA is an immediate constant offset to be
 177        added to THIS.  If VCALL_OFFSET is nonzero, the word at
 178        *(*this + vcall_offset) should be added to THIS.  */
 179     void (* output_mi_thunk) (FILE *file, tree thunk_decl,
 180                               HOST_WIDE_INT delta, HOST_WIDE_INT vcall_offset,
 181                               tree function_decl);
 182
 183     /* Determine whether output_mi_thunk would succeed.  */
 184     /* ??? Ideally, this hook would not exist, and success or failure
 185        would be returned from output_mi_thunk directly.  But there's
 186        too much undo-able setup involved in invoking output_mi_thunk.
 187        Could be fixed by making output_mi_thunk emit rtl instead of
 188        text to the output file.  */
 189     bool (* can_output_mi_thunk) (tree thunk_decl, HOST_WIDE_INT delta,
 190                                   HOST_WIDE_INT vcall_offset,
 191                                   tree function_decl);
 192
 193     /* Output any boilerplate text needed at the beginning of a
 194        translation unit.  */
 195     void (*file_start) (void);
 196
 197     /* Output any boilerplate text needed at the end of a
 198        translation unit.  */
 199     void (*file_end) (void);
 200
 201     /* Output an assembler pseudo-op to declare a library function name
 202        external.  */
 203     void (*external_libcall) (rtx);
 204
 205      /* Output an assembler directive to mark decl live. This instructs
 206         linker to not dead code strip this symbol.  */
 207     void (*mark_decl_preserved) (const char *);
 208
 209     /* Output the definition of a section anchor.  */
 210     void (*output_anchor) (rtx);
 211
 212     /* Output a DTP-relative reference to a TLS symbol.  */
 213     void (*output_dwarf_dtprel) (FILE *file, int size, rtx x);
 214
 215   } asm_out;
 216
 217   /* Functions relating to instruction scheduling.  */
 218   struct sched
 219   {
 220     /* Given the current cost, COST, of an insn, INSN, calculate and
 221        return a new cost based on its relationship to DEP_INSN through
 222        the dependence LINK.  The default is to make no adjustment.  */
 223     int (* adjust_cost) (rtx insn, rtx link, rtx def_insn, int cost);
 224
 225     /* Adjust the priority of an insn as you see fit.  Returns the new
 226        priority.  */
 227     int (* adjust_priority) (rtx, int);
 228
 229     /* Function which returns the maximum number of insns that can be
 230        scheduled in the same machine cycle.  This must be constant
 231        over an entire compilation.  The default is 1.  */
 232     int (* issue_rate) (void);
 233
 234     /* Calculate how much this insn affects how many more insns we
 235        can emit this cycle.  Default is they all cost the same.  */
 236     int (* variable_issue) (FILE *, int, rtx, int);
 237
 238     /* Initialize machine-dependent scheduling code.  */
 239     void (* md_init) (FILE *, int, int);
 240
 241     /* Finalize machine-dependent scheduling code.  */
 242     void (* md_finish) (FILE *, int);
 243
 244     /* Initialize machine-dependent function while scheduling code.  */
 245     void (* md_init_global) (FILE *, int, int);
 246
 247     /* Finalize machine-dependent function wide scheduling code.  */
 248     void (* md_finish_global) (FILE *, int);
 249
 250     /* Reorder insns in a machine-dependent fashion, in two different
 251        places.  Default does nothing.  */
 252     int (* reorder) (FILE *, int, rtx *, int *, int);
 253     int (* reorder2) (FILE *, int, rtx *, int *, int);
 254
 255     /* The following member value is a pointer to a function called
 256        after evaluation forward dependencies of insns in chain given
 257        by two parameter values (head and tail correspondingly).  */
 258     void (* dependencies_evaluation_hook) (rtx, rtx);
 259
 260     /* The values of the following four members are pointers to
 261        functions used to simplify the automaton descriptions.
 262        dfa_pre_cycle_insn and dfa_post_cycle_insn give functions
 263        returning insns which are used to change the pipeline hazard
 264        recognizer state when the new simulated processor cycle
 265        correspondingly starts and finishes.  The function defined by
 266        init_dfa_pre_cycle_insn and init_dfa_post_cycle_insn are used
 267        to initialize the corresponding insns.  The default values of
 268        the members result in not changing the automaton state when
 269        the new simulated processor cycle correspondingly starts and
 270        finishes.  */
 271     void (* init_dfa_pre_cycle_insn) (void);
 272     rtx (* dfa_pre_cycle_insn) (void);
 273     void (* init_dfa_post_cycle_insn) (void);
 274     rtx (* dfa_post_cycle_insn) (void);
 275
 276     /* The following member value is a pointer to a function returning value
 277        which defines how many insns in queue `ready' will we try for
 278        multi-pass scheduling.  If the member value is nonzero and the
 279        function returns positive value, the DFA based scheduler will make
 280        multi-pass scheduling for the first cycle.  In other words, we will
 281        try to choose ready insn which permits to start maximum number of
 282        insns on the same cycle.  */
 283     int (* first_cycle_multipass_dfa_lookahead) (void);
 284
 285     /* The following member value is pointer to a function controlling
 286        what insns from the ready insn queue will be considered for the
 287        multipass insn scheduling.  If the hook returns zero for insn
 288        passed as the parameter, the insn will be not chosen to be
 289        issued.  */
 290     int (* first_cycle_multipass_dfa_lookahead_guard) (rtx);
 291
 292     /* The following member value is pointer to a function called by
 293        the insn scheduler before issuing insn passed as the third
 294        parameter on given cycle.  If the hook returns nonzero, the
 295        insn is not issued on given processors cycle.  Instead of that,
 296        the processor cycle is advanced.  If the value passed through
 297        the last parameter is zero, the insn ready queue is not sorted
 298        on the new cycle start as usually.  The first parameter passes
 299        file for debugging output.  The second one passes the scheduler
 300        verbose level of the debugging output.  The forth and the fifth
 301        parameter values are correspondingly processor cycle on which
 302        the previous insn has been issued and the current processor
 303        cycle.  */
 304     int (* dfa_new_cycle) (FILE *, int, rtx, int, int, int *);
 305
 306     /* The following member value is a pointer to a function called
 307        by the insn scheduler.  It should return true if there exists a
 308        dependence which is considered costly by the target, between
 309        the insn passed as the first parameter, and the insn passed as
 310        the second parameter.  The third parameter is the INSN_DEPEND
 311        link that represents the dependence between the two insns.  The
 312        fourth argument is the cost of the dependence as estimated by
 313        the scheduler.  The last argument is the distance in cycles
 314        between the already scheduled insn (first parameter) and the
 315        the second insn (second parameter).  */
 316     bool (* is_costly_dependence) (rtx, rtx, rtx, int, int);
 317
 318     /* Given the current cost, COST, of an insn, INSN, calculate and
 319        return a new cost based on its relationship to DEP_INSN through the
 320        dependence of type DEP_TYPE.  The default is to make no adjustment.  */
 321     int (* adjust_cost_2) (rtx insn, int, rtx def_insn, int cost);
 322
 323     /* The following member value is a pointer to a function called
 324        by the insn scheduler. This hook is called to notify the backend
 325        that new instructions were emitted.  */
 326     void (* h_i_d_extended) (void);
 327
 328     /* The following member value is a pointer to a function called
 329        by the insn scheduler.
 330        The first parameter is an instruction, the second parameter is the type
 331        of the requested speculation, and the third parameter is a pointer to the
 332        speculative pattern of the corresponding type (set if return value == 1).
 333        It should return
 334        -1, if there is no pattern, that will satisfy the requested speculation
 335        type,
 336        0, if current pattern satisfies the requested speculation type,
 337        1, if pattern of the instruction should be changed to the newly
 338        generated one.  */
 339     int (* speculate_insn) (rtx, int, rtx *);
 340
 341     /* The following member value is a pointer to a function called
 342        by the insn scheduler.  It should return true if the check instruction
 343        corresponding to the instruction passed as the parameter needs a
 344        recovery block.  */
 345     bool (* needs_block_p) (rtx);
 346
 347     /* The following member value is a pointer to a function called
 348        by the insn scheduler.  It should return a pattern for the check
 349        instruction.
 350        The first parameter is a speculative instruction, the second parameter
 351        is the label of the corresponding recovery block (or null, if it is a
 352        simple check).  If the mutation of the check is requested (e.g. from
 353        ld.c to chk.a), the third parameter is true - in this case the first
 354        parameter is the previous check.  */
 355     rtx (* gen_check) (rtx, rtx, bool);
 356
 357     /* The following member value is a pointer to a function controlling
 358        what insns from the ready insn queue will be considered for the
 359        multipass insn scheduling.  If the hook returns zero for the insn
 360        passed as the parameter, the insn will not be chosen to be
 361        issued.  This hook is used to discard speculative instructions,
 362        that stand at the first position of the ready list.  */
 363     bool (* first_cycle_multipass_dfa_lookahead_guard_spec) (rtx);
 364
 365     /* The following member value is a pointer to a function that provides
 366        information about the speculation capabilities of the target.
 367        The parameter is a pointer to spec_info variable.  */
 368     void (* set_sched_flags) (struct spec_info_def *);
 369   } sched;
 370
 371   /* Functions relating to vectorization.  */
 372   struct vectorize
 373   {
 374     /* The following member value is a pointer to a function called
 375        by the vectorizer, and return the decl of the target builtin
 376        function.  */
 377     tree (* builtin_mask_for_load) (void);
 378   } vectorize;
 379
 380   /* The initial value of target_flags.  */
 381   int default_target_flags;
 382
 383   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
 384      passed to the switch; it is NULL if no argument was.  VALUE is the
 385      value of ARG if CODE specifies a UInteger option, otherwise it is
 386      1 if the positive form of the switch was used and 0 if the negative
 387      form was.  Return true if the switch was valid.  */
 388   bool (* handle_option) (size_t code, const char *arg, int value);
 389
 390   /* Return machine mode for filter value.  */
 391   enum machine_mode (* eh_return_filter_mode) (void);
 392
 393   /* Given two decls, merge their attributes and return the result.  */
 394   tree (* merge_decl_attributes) (tree, tree);
 395
 396   /* Given two types, merge their attributes and return the result.  */
 397   tree (* merge_type_attributes) (tree, tree);
 398
 399   /* Table of machine attributes and functions to handle them.
 400      Ignored if NULL.  */
 401   const struct attribute_spec *attribute_table;
 402
 403   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 404      one if they are compatible and two if they are nearly compatible
 405      (which causes a warning to be generated).  */
 406   int (* comp_type_attributes) (tree type1, tree type2);
 407
 408   /* Assign default attributes to the newly defined TYPE.  */
 409   void (* set_default_type_attributes) (tree type);
 410
 411   /* Insert attributes on the newly created DECL.  */
 412   void (* insert_attributes) (tree decl, tree *attributes);
 413
 414   /* Return true if FNDECL (which has at least one machine attribute)
 415      can be inlined despite its machine attributes, false otherwise.  */
 416   bool (* function_attribute_inlinable_p) (tree fndecl);
 417
 418   /* Return true if bitfields in RECORD_TYPE should follow the
 419      Microsoft Visual C++ bitfield layout rules.  */
 420   bool (* ms_bitfield_layout_p) (tree record_type);
 421
 422   /* True if the target supports decimal floating point.  */
 423   bool (* decimal_float_supported_p) (void);
 424
 425   /* Return true if anonymous bitfields affect structure alignment.  */
 426   bool (* align_anon_bitfield) (void);
 427
 428   /* Return true if volatile bitfields should use the narrowest type possible.
 429      Return false if they should use the container type.  */
 430   bool (* narrow_volatile_bitfield) (void);
 431
 432   /* Set up target-specific built-in functions.  */
 433   void (* init_builtins) (void);
 434
 435   /* Expand a target-specific builtin.  */
 436   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 437                           enum machine_mode mode, int ignore);
 438
 439   /* Select a replacement for a target-specific builtin.  This is done
 440      *before* regular type checking, and so allows the target to implement
 441      a crude form of function overloading.  The result is a complete
 442      expression that implements the operation.  */
 443   tree (*resolve_overloaded_builtin) (tree decl, tree params);
 444
 445   /* Fold a target-specific builtin.  */
 446   tree (* fold_builtin) (tree fndecl, tree arglist, bool ignore);
 447
 448   /* For a vendor-specific fundamental TYPE, return a pointer to
 449      a statically-allocated string containing the C++ mangling for
 450      TYPE.  In all other cases, return NULL.  */
 451   const char * (* mangle_fundamental_type) (tree type);
 452
 453   /* Make any adjustments to libfunc names needed for this target.  */
 454   void (* init_libfuncs) (void);
 455
 456   /* Given a decl, a section name, and whether the decl initializer
 457      has relocs, choose attributes for the section.  */
 458   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 459   unsigned int (* section_type_flags) (tree, const char *, int);
 460
 461   /* True if new jumps cannot be created, to replace existing ones or
 462      not, at the current point in the compilation.  */
 463   bool (* cannot_modify_jumps_p) (void);
 464
 465   /* Return a register class for which branch target register
 466      optimizations should be applied.  */
 467   int (* branch_target_register_class) (void);
 468
 469   /* Return true if branch target register optimizations should include
 470      callee-saved registers that are not already live during the current
 471      function.  AFTER_PE_GEN is true if prologues and epilogues have
 472      already been generated.  */
 473   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 474
 475   /* True if the constant X cannot be placed in the constant pool.  */
 476   bool (* cannot_force_const_mem) (rtx);
 477
 478   /* True if the insn X cannot be duplicated.  */
 479   bool (* cannot_copy_insn_p) (rtx);
 480
 481   /* True if X is considered to be commutative.  */
 482   bool (* commutative_p) (rtx, int);
 483
 484   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 485   rtx (* delegitimize_address) (rtx);
 486
 487   /* True if the given constant can be put into an object_block.  */
 488   bool (* use_blocks_for_constant_p) (enum machine_mode, rtx);
 489
 490   /* The minimum and maximum byte offsets for anchored addresses.  */
 491   HOST_WIDE_INT min_anchor_offset;
 492   HOST_WIDE_INT max_anchor_offset;
 493
 494   /* True if section anchors can be used to access the given symbol.  */
 495   bool (* use_anchors_for_symbol_p) (rtx);
 496
 497   /* True if it is OK to do sibling call optimization for the specified
 498      call expression EXP.  DECL will be the called function, or NULL if
 499      this is an indirect call.  */
 500   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 501
 502   /* True if EXP should be placed in a "small data" section.  */
 503   bool (* in_small_data_p) (tree);
 504
 505   /* True if EXP names an object for which name resolution must resolve
 506      to the current module.  */
 507   bool (* binds_local_p) (tree);
 508
 509   /* Do something target-specific to record properties of the DECL into
 510      the associated SYMBOL_REF.  */
 511   void (* encode_section_info) (tree, rtx, int);
 512
 513   /* Undo the effects of encode_section_info on the symbol string.  */
 514   const char * (* strip_name_encoding) (const char *);
 515
 516   /* If shift optabs for MODE are known to always truncate the shift count,
 517      return the mask that they apply.  Return 0 otherwise.  */
 518   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
 519
 520   /* Return the number of divisions in the given MODE that should be present,
 521      so that it is profitable to turn the division into a multiplication by
 522      the reciprocal.  */
 523   unsigned int (* min_divisions_for_recip_mul) (enum machine_mode mode);
 524
 525   /* If the representation of integral MODE is such that values are
 526      always sign-extended to a wider mode MODE_REP then return
 527      SIGN_EXTEND.  Return UNKNOWN otherwise.  */
 528   /* Note that the return type ought to be RTX_CODE, but that's not
 529      necessarily defined at this point.  */
 530   int (* mode_rep_extended) (enum machine_mode mode,
 531                              enum machine_mode mode_rep);
 532
 533   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 534   bool (* valid_pointer_mode) (enum machine_mode mode);
 535
 536   /* True if MODE is valid for the target.  By "valid", we mean able to
 537      be manipulated in non-trivial ways.  In particular, this means all
 538      the arithmetic is supported.  */
 539   bool (* scalar_mode_supported_p) (enum machine_mode mode);
 540
 541   /* Similarly for vector modes.  "Supported" here is less strict.  At
 542      least some operations are supported; need to check optabs or builtins
 543      for further details.  */
 544   bool (* vector_mode_supported_p) (enum machine_mode mode);
 545
 546   /* True if a vector is opaque.  */
 547   bool (* vector_opaque_p) (tree);
 548
 549   /* Compute a (partial) cost for rtx X.  Return true if the complete
 550      cost has been computed, and false if subexpressions should be
 551      scanned.  In either case, *TOTAL contains the cost result.  */
 552   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 553      not necessarily defined at this point.  */
 554   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 555
 556   /* Compute the cost of X, used as an address.  Never called with
 557      invalid addresses.  */
 558   int (* address_cost) (rtx x);
 559
 560   /* Return where to allocate pseudo for a given hard register initial
 561      value.  */
 562   rtx (* allocate_initial_value) (rtx x);
 563
 564   /* Given a register, this hook should return a parallel of registers
 565      to represent where to find the register pieces.  Define this hook
 566      if the register and its mode are represented in Dwarf in
 567      non-contiguous locations, or if the register should be
 568      represented in more than one register in Dwarf.  Otherwise, this
 569      hook should return NULL_RTX.  */
 570   rtx (* dwarf_register_span) (rtx);
 571
 572   /* Fetch the fixed register(s) which hold condition codes, for
 573      targets where it makes sense to look for duplicate assignments to
 574      the condition codes.  This should return true if there is such a
 575      register, false otherwise.  The arguments should be set to the
 576      fixed register numbers.  Up to two condition code registers are
 577      supported.  If there is only one for this target, the int pointed
 578      at by the second argument should be set to -1.  */
 579   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 580
 581   /* If two condition code modes are compatible, return a condition
 582      code mode which is compatible with both, such that a comparison
 583      done in the returned mode will work for both of the original
 584      modes.  If the condition code modes are not compatible, return
 585      VOIDmode.  */
 586   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 587                                              enum machine_mode);
 588
 589   /* Do machine-dependent code transformations.  Called just before
 590      delayed-branch scheduling.  */
 591   void (* machine_dependent_reorg) (void);
 592
 593   /* Create the __builtin_va_list type.  */
 594   tree (* build_builtin_va_list) (void);
 595
 596   /* Gimplifies a VA_ARG_EXPR.  */
 597   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 598                                  tree *post_p);
 599
 600   /* Validity-checking routines for PCH files, target-specific.
 601      get_pch_validity returns a pointer to the data to be stored,
 602      and stores the size in its argument.  pch_valid_p gets the same
 603      information back and returns NULL if the PCH is valid,
 604      or an error message if not.
 605   */
 606   void * (* get_pch_validity) (size_t *);
 607   const char * (* pch_valid_p) (const void *, size_t);
 608
 609   /* If nonnull, this function checks whether a PCH file with the
 610      given set of target flags can be used.  It returns NULL if so,
 611      otherwise it returns an error message.  */
 612   const char *(*check_pch_target_flags) (int);
 613
 614   /* True if the compiler should give an enum type only as many
 615      bytes as it takes to represent the range of possible values of
 616      that type.  */
 617   bool (* default_short_enums) (void);
 618
 619   /* This target hook returns an rtx that is used to store the address
 620      of the current frame into the built-in setjmp buffer.  */
 621   rtx (* builtin_setjmp_frame_value) (void);
 622
 623   /* This target hook should add STRING_CST trees for any hard regs
 624      the port wishes to automatically clobber for an asm.  */
 625   tree (* md_asm_clobbers) (tree, tree, tree);
 626
 627   /* This target hook allows the backend to specify a calling convention
 628      in the debug information.  This function actually returns an
 629      enum dwarf_calling_convention, but because of forward declarations
 630      and not wanting to include dwarf2.h everywhere target.h is included
 631      the function is being declared as an int.  */
 632   int (* dwarf_calling_convention) (tree);
 633
 634   /* This target hook allows the backend to emit frame-related insns that
 635      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
 636      engine will invoke it on insns of the form
 637        (set (reg) (unspec [...] UNSPEC_INDEX))
 638      and
 639        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
 640      to let the backend emit the call frame instructions.  */
 641   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
 642
 643   /* Perform architecture specific checking of statements gimplified
 644      from VA_ARG_EXPR.  LHS is left hand side of MODIFY_EXPR, RHS
 645      is right hand side.  Returns true if the statements doesn't need
 646      to be checked for va_list references.  */
 647   bool (* stdarg_optimize_hook) (struct stdarg_info *ai, tree lhs, tree rhs);
 648
 649   /* This target hook allows the operating system to override the DECL
 650      that represents the external variable that contains the stack
 651      protection guard variable.  The type of this DECL is ptr_type_node.  */
 652   tree (* stack_protect_guard) (void);
 653
 654   /* This target hook allows the operating system to override the CALL_EXPR
 655      that is invoked when a check vs the guard variable fails.  */
 656   tree (* stack_protect_fail) (void);
 657
 658   /* Returns NULL if target supports the insn within a doloop block,
 659      otherwise it returns an error message.  */
 660   const char * (*invalid_within_doloop) (rtx);
 661
 662   /* DECL is a variable or function with __attribute__((dllimport))
 663      specified.  Use this hook if the target needs to add extra validation
 664      checks to  handle_dll_attribute ().  */
 665   bool (* valid_dllimport_attribute_p) (tree decl);
 666
 667   /* Functions relating to calls - argument passing, returns, etc.  */
 668   struct calls {
 669     bool (*promote_function_args) (tree fntype);
 670     bool (*promote_function_return) (tree fntype);
 671     bool (*promote_prototypes) (tree fntype);
 672     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 673     bool (*return_in_memory) (tree type, tree fndecl);
 674     bool (*return_in_msb) (tree type);
 675
 676     /* Return true if a parameter must be passed by reference.  TYPE may
 677        be null if this is a libcall.  CA may be null if this query is
 678        from __builtin_va_arg.  */
 679     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 680                                tree type, bool named_arg);
 681
 682     rtx (*expand_builtin_saveregs) (void);
 683     /* Returns pretend_argument_size.  */
 684     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 685                                     tree type, int *pretend_arg_size,
 686                                     int second_time);
 687     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 688     /* Returns true if we should use
 689        targetm.calls.setup_incoming_varargs() and/or
 690        targetm.calls.strict_argument_naming().  */
 691     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 692
 693     /* Given a complex type T, return true if a parameter of type T
 694        should be passed as two scalars.  */
 695     bool (* split_complex_arg) (tree type);
 696
 697     /* Return true if type T, mode MODE, may not be passed in registers,
 698        but must be passed on the stack.  */
 699     /* ??? This predicate should be applied strictly after pass-by-reference.
 700        Need audit to verify that this is the case.  */
 701     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 702
 703     /* Return true if type TYPE, mode MODE, which is passed by reference,
 704        should have the object copy generated by the callee rather than
 705        the caller.  It is never called for TYPE requiring constructors.  */
 706     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 707                             tree type, bool named);
 708
 709     /* Return zero for arguments passed entirely on the stack or entirely
 710        in registers.  If passed in both, return the number of bytes passed
 711        in registers; the balance is therefore passed on the stack.  */
 712     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 713                                tree type, bool named);
 714
 715     /* Return the diagnostic message string if function without a prototype
 716        is not allowed for this 'val' argument; NULL otherwise. */
 717     const char *(*invalid_arg_for_unprototyped_fn) (tree typelist,
 718                                                     tree funcdecl, tree val);
 719
 720     /* Return an rtx for the return value location of the function
 721        specified by FN_DECL_OR_TYPE with a return type of RET_TYPE.  */
 722     rtx (*function_value) (tree ret_type, tree fn_decl_or_type,
 723                            bool outgoing);
 724
 725     /* Return an rtx for the argument pointer incoming to the
 726        current function.  */
 727     rtx (*internal_arg_pointer) (void);
 728   } calls;
 729
 730   /* Return the diagnostic message string if conversion from FROMTYPE
 731      to TOTYPE is not allowed, NULL otherwise.  */
 732   const char *(*invalid_conversion) (tree fromtype, tree totype);
 733
 734   /* Return the diagnostic message string if the unary operation OP is
 735      not permitted on TYPE, NULL otherwise.  */
 736   const char *(*invalid_unary_op) (int op, tree type);
 737
 738   /* Return the diagnostic message string if the binary operation OP
 739      is not permitted on TYPE1 and TYPE2, NULL otherwise.  */
 740   const char *(*invalid_binary_op) (int op, tree type1, tree type2);
 741
 742   /* Return the class for a secondary reload, and fill in extra information.  */
 743   enum reg_class (*secondary_reload) (bool, rtx, enum reg_class,
 744                                       enum machine_mode,
 745                                       struct secondary_reload_info *);
 746
 747   /* Functions specific to the C++ frontend.  */
 748   struct cxx {
 749     /* Return the integer type used for guard variables.  */
 750     tree (*guard_type) (void);
 751     /* Return true if only the low bit of the guard should be tested.  */
 752     bool (*guard_mask_bit) (void);
 753     /* Returns the size of the array cookie for an array of type.  */
 754     tree (*get_cookie_size) (tree);
 755     /* Returns true if the element size should be stored in the
 756        array cookie.  */
 757     bool (*cookie_has_size) (void);
 758     /* Allows backends to perform additional processing when
 759        deciding if a class should be exported or imported.  */
 760     int (*import_export_class) (tree, int);
 761     /* Returns true if constructors and destructors return "this".  */
 762     bool (*cdtor_returns_this) (void);
 763     /* Returns true if the key method for a class can be an inline
 764        function, so long as it is not declared inline in the class
 765        itself.  Returning true is the behavior required by the Itanium
 766        C++ ABI.  */
 767     bool (*key_method_may_be_inline) (void);
 768     /* DECL is a virtual table, virtual table table, typeinfo object,
 769        or other similar implicit class data object that will be
 770        emitted with external linkage in this translation unit.  No ELF
 771        visibility has been explicitly specified.  If the target needs
 772        to specify a visibility other than that of the containing class,
 773        use this hook to set DECL_VISIBILITY and
 774        DECL_VISIBILITY_SPECIFIED.  */
 775     void (*determine_class_data_visibility) (tree decl);
 776     /* Returns true (the default) if virtual tables and other
 777        similar implicit class data objects are always COMDAT if they
 778        have external linkage.  If this hook returns false, then
 779        class data for classes whose virtual table will be emitted in
 780        only one translation unit will not be COMDAT.  */
 781     bool (*class_data_always_comdat) (void);
 782     /* Returns true if __aeabi_atexit should be used to register static
 783        destructors.  */
 784     bool (*use_aeabi_atexit) (void);
 785     /* TYPE is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that
 786        has just been defined.  Use this hook to make adjustments to the
 787        class  (eg, tweak visibility or perform any other required
 788        target modifications).  */
 789     void (*adjust_class_at_definition) (tree type);
 790   } cxx;
 791
 792   /* For targets that need to mark extra registers as live on entry to
 793      the function, they should define this target hook and set their
 794      bits in the bitmap passed in. */
 795   void (*live_on_entry) (bitmap);
 796
 797   /* True if unwinding tables should be generated by default.  */
 798   bool unwind_tables_default;
 799
 800   /* Leave the boolean fields at the end.  */
 801
 802   /* True if arbitrary sections are supported.  */
 803   bool have_named_sections;
 804
 805   /* True if we can create zeroed data by switching to a BSS section
 806      and then using ASM_OUTPUT_SKIP to allocate the space.  */
 807   bool have_switchable_bss_sections;
 808
 809   /* True if "native" constructors and destructors are supported,
 810      false if we're using collect2 for the job.  */
 811   bool have_ctors_dtors;
 812
 813   /* True if thread-local storage is supported.  */
 814   bool have_tls;
 815
 816   /* True if a small readonly data section is supported.  */
 817   bool have_srodata_section;
 818
 819   /* True if EH frame info sections should be zero-terminated.  */
 820   bool terminate_dw2_eh_frame_info;
 821
 822   /* True if #NO_APP should be emitted at the beginning of
 823      assembly output.  */
 824   bool file_start_app_off;
 825
 826   /* True if output_file_directive should be called for main_input_filename
 827      at the beginning of assembly output.  */
 828   bool file_start_file_directive;
 829
 830   /* True if #pragma redefine_extname is to be supported.  */
 831   bool handle_pragma_redefine_extname;
 832
 833   /* True if #pragma extern_prefix is to be supported.  */
 834   bool handle_pragma_extern_prefix;
 835
 836   /* True if the target is allowed to reorder memory accesses unless
 837      synchronization is explicitly requested.  */
 838   bool relaxed_ordering;
 839
 840   /* Returns true if we should generate exception tables for use with the
 841      ARM EABI.  The effects the encoding of function exception specifications.
 842    */
 843   bool arm_eabi_unwinder;
 844
 845   /* Leave the boolean fields at the end.  */
 846 };
 847
 848 extern struct gcc_target targetm;
 849
 850 #endif /* GCC_TARGET_H */