gcc/target.h

   1 /* Data structure definitions for a generic GCC target.
   2    Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006
   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 section for EXP.  It may be a DECL or a constant.  RELOC
 145        is nonzero if runtime relocations must be applied; bit 1 will be
 146        set if the runtime relocations require non-local name resolution.
 147        ALIGN is the required alignment of the data.  */
 148     section *(* select_section) (tree, int, unsigned HOST_WIDE_INT);
 149
 150     /* Return a section for X.  MODE is X's mode and ALIGN is its
 151        alignment in bits.  */
 152     section *(* select_rtx_section) (enum machine_mode, rtx,
 153                                      unsigned HOST_WIDE_INT);
 154
 155     /* Select a unique section name for DECL.  RELOC is the same as
 156        for SELECT_SECTION.  */
 157     void (* unique_section) (tree, int);
 158
 159     /* Return the readonly data section associated with function DECL.  */
 160     section *(* function_rodata_section) (tree);
 161
 162     /* Output a constructor for a symbol with a given priority.  */
 163     void (* constructor) (rtx, int);
 164
 165     /* Output a destructor for a symbol with a given priority.  */
 166     void (* destructor) (rtx, int);
 167
 168     /* Output the assembler code for a thunk function.  THUNK_DECL is the
 169        declaration for the thunk function itself, FUNCTION is the decl for
 170        the target function.  DELTA is an immediate constant offset to be
 171        added to THIS.  If VCALL_OFFSET is nonzero, the word at
 172        *(*this + vcall_offset) should be added to THIS.  */
 173     void (* output_mi_thunk) (FILE *file, tree thunk_decl,
 174                               HOST_WIDE_INT delta, HOST_WIDE_INT vcall_offset,
 175                               tree function_decl);
 176
 177     /* Determine whether output_mi_thunk would succeed.  */
 178     /* ??? Ideally, this hook would not exist, and success or failure
 179        would be returned from output_mi_thunk directly.  But there's
 180        too much undo-able setup involved in invoking output_mi_thunk.
 181        Could be fixed by making output_mi_thunk emit rtl instead of
 182        text to the output file.  */
 183     bool (* can_output_mi_thunk) (tree thunk_decl, HOST_WIDE_INT delta,
 184                                   HOST_WIDE_INT vcall_offset,
 185                                   tree function_decl);
 186
 187     /* Output any boilerplate text needed at the beginning of a
 188        translation unit.  */
 189     void (*file_start) (void);
 190
 191     /* Output any boilerplate text needed at the end of a
 192        translation unit.  */
 193     void (*file_end) (void);
 194
 195     /* Output an assembler pseudo-op to declare a library function name
 196        external.  */
 197     void (*external_libcall) (rtx);
 198
 199      /* Output an assembler directive to mark decl live. This instructs
 200         linker to not dead code strip this symbol.  */
 201     void (*mark_decl_preserved) (const char *);
 202
 203     /* Output the definition of a section anchor.  */
 204     void (*output_anchor) (rtx);
 205
 206     /* Output a DTP-relative reference to a TLS symbol.  */
 207     void (*output_dwarf_dtprel) (FILE *file, int size, rtx x);
 208
 209   } asm_out;
 210
 211   /* Functions relating to instruction scheduling.  */
 212   struct sched
 213   {
 214     /* Given the current cost, COST, of an insn, INSN, calculate and
 215        return a new cost based on its relationship to DEP_INSN through
 216        the dependence LINK.  The default is to make no adjustment.  */
 217     int (* adjust_cost) (rtx insn, rtx link, rtx def_insn, int cost);
 218
 219     /* Adjust the priority of an insn as you see fit.  Returns the new
 220        priority.  */
 221     int (* adjust_priority) (rtx, int);
 222
 223     /* Function which returns the maximum number of insns that can be
 224        scheduled in the same machine cycle.  This must be constant
 225        over an entire compilation.  The default is 1.  */
 226     int (* issue_rate) (void);
 227
 228     /* Calculate how much this insn affects how many more insns we
 229        can emit this cycle.  Default is they all cost the same.  */
 230     int (* variable_issue) (FILE *, int, rtx, int);
 231
 232     /* Initialize machine-dependent scheduling code.  */
 233     void (* md_init) (FILE *, int, int);
 234
 235     /* Finalize machine-dependent scheduling code.  */
 236     void (* md_finish) (FILE *, int);
 237
 238     /* Initialize machine-dependent function while scheduling code.  */
 239     void (* md_init_global) (FILE *, int, int);
 240
 241     /* Finalize machine-dependent function wide scheduling code.  */
 242     void (* md_finish_global) (FILE *, int);
 243
 244     /* Reorder insns in a machine-dependent fashion, in two different
 245        places.  Default does nothing.  */
 246     int (* reorder) (FILE *, int, rtx *, int *, int);
 247     int (* reorder2) (FILE *, int, rtx *, int *, int);
 248
 249     /* The following member value is a pointer to a function called
 250        after evaluation forward dependencies of insns in chain given
 251        by two parameter values (head and tail correspondingly).  */
 252     void (* dependencies_evaluation_hook) (rtx, rtx);
 253
 254     /* The values of the following four members are pointers to
 255        functions used to simplify the automaton descriptions.
 256        dfa_pre_cycle_insn and dfa_post_cycle_insn give functions
 257        returning insns which are used to change the pipeline hazard
 258        recognizer state when the new simulated processor cycle
 259        correspondingly starts and finishes.  The function defined by
 260        init_dfa_pre_cycle_insn and init_dfa_post_cycle_insn are used
 261        to initialize the corresponding insns.  The default values of
 262        the members result in not changing the automaton state when
 263        the new simulated processor cycle correspondingly starts and
 264        finishes.  */
 265     void (* init_dfa_pre_cycle_insn) (void);
 266     rtx (* dfa_pre_cycle_insn) (void);
 267     void (* init_dfa_post_cycle_insn) (void);
 268     rtx (* dfa_post_cycle_insn) (void);
 269
 270     /* The following member value is a pointer to a function returning value
 271        which defines how many insns in queue `ready' will we try for
 272        multi-pass scheduling.  If the member value is nonzero and the
 273        function returns positive value, the DFA based scheduler will make
 274        multi-pass scheduling for the first cycle.  In other words, we will
 275        try to choose ready insn which permits to start maximum number of
 276        insns on the same cycle.  */
 277     int (* first_cycle_multipass_dfa_lookahead) (void);
 278
 279     /* The following member value is pointer to a function controlling
 280        what insns from the ready insn queue will be considered for the
 281        multipass insn scheduling.  If the hook returns zero for insn
 282        passed as the parameter, the insn will be not chosen to be
 283        issued.  */
 284     int (* first_cycle_multipass_dfa_lookahead_guard) (rtx);
 285
 286     /* The following member value is pointer to a function called by
 287        the insn scheduler before issuing insn passed as the third
 288        parameter on given cycle.  If the hook returns nonzero, the
 289        insn is not issued on given processors cycle.  Instead of that,
 290        the processor cycle is advanced.  If the value passed through
 291        the last parameter is zero, the insn ready queue is not sorted
 292        on the new cycle start as usually.  The first parameter passes
 293        file for debugging output.  The second one passes the scheduler
 294        verbose level of the debugging output.  The forth and the fifth
 295        parameter values are correspondingly processor cycle on which
 296        the previous insn has been issued and the current processor
 297        cycle.  */
 298     int (* dfa_new_cycle) (FILE *, int, rtx, int, int, int *);
 299
 300     /* The following member value is a pointer to a function called
 301        by the insn scheduler.  It should return true if there exists a
 302        dependence which is considered costly by the target, between
 303        the insn passed as the first parameter, and the insn passed as
 304        the second parameter.  The third parameter is the INSN_DEPEND
 305        link that represents the dependence between the two insns.  The
 306        fourth argument is the cost of the dependence as estimated by
 307        the scheduler.  The last argument is the distance in cycles
 308        between the already scheduled insn (first parameter) and the
 309        the second insn (second parameter).  */
 310     bool (* is_costly_dependence) (rtx, rtx, rtx, int, int);
 311
 312     /* Given the current cost, COST, of an insn, INSN, calculate and
 313        return a new cost based on its relationship to DEP_INSN through the
 314        dependence of type DEP_TYPE.  The default is to make no adjustment.  */
 315     int (* adjust_cost_2) (rtx insn, int, rtx def_insn, int cost);
 316
 317     /* The following member value is a pointer to a function called
 318        by the insn scheduler. This hook is called to notify the backend
 319        that new instructions were emitted.  */
 320     void (* h_i_d_extended) (void);
 321
 322     /* The following member value is a pointer to a function called
 323        by the insn scheduler.
 324        The first parameter is an instruction, the second parameter is the type
 325        of the requested speculation, and the third parameter is a pointer to the
 326        speculative pattern of the corresponding type (set if return value == 1).
 327        It should return
 328        -1, if there is no pattern, that will satisfy the requested speculation
 329        type,
 330        0, if current pattern satisfies the requested speculation type,
 331        1, if pattern of the instruction should be changed to the newly
 332        generated one.  */
 333     int (* speculate_insn) (rtx, int, rtx *);
 334
 335     /* The following member value is a pointer to a function called
 336        by the insn scheduler.  It should return true if the check instruction
 337        corresponding to the instruction passed as the parameter needs a
 338        recovery block.  */
 339     bool (* needs_block_p) (rtx);
 340
 341     /* The following member value is a pointer to a function called
 342        by the insn scheduler.  It should return a pattern for the check
 343        instruction.
 344        The first parameter is a speculative instruction, the second parameter
 345        is the label of the corresponding recovery block (or null, if it is a
 346        simple check).  If the mutation of the check is requested (e.g. from
 347        ld.c to chk.a), the third parameter is true - in this case the first
 348        parameter is the previous check.  */
 349     rtx (* gen_check) (rtx, rtx, bool);
 350
 351     /* The following member value is a pointer to a function controlling
 352        what insns from the ready insn queue will be considered for the
 353        multipass insn scheduling.  If the hook returns zero for the insn
 354        passed as the parameter, the insn will not be chosen to be
 355        issued.  This hook is used to discard speculative instructions,
 356        that stand at the first position of the ready list.  */
 357     bool (* first_cycle_multipass_dfa_lookahead_guard_spec) (rtx);
 358
 359     /* The following member value is a pointer to a function that provides
 360        information about the speculation capabilities of the target.
 361        The parameter is a pointer to spec_info variable.  */
 362     void (* set_sched_flags) (struct spec_info_def *);
 363   } sched;
 364
 365   /* Functions relating to vectorization.  */
 366   struct vectorize
 367   {
 368     /* The following member value is a pointer to a function called
 369        by the vectorizer, and return the decl of the target builtin
 370        function.  */
 371     tree (* builtin_mask_for_load) (void);
 372
 373     /* Target builtin that implements vector widening multiplication.
 374        builtin_mul_widen_eve computes the element-by-element products
 375        for the even elements, and builtin_mul_widen_odd computes the
 376        element-by-element products for the odd elements.  */
 377     tree (* builtin_mul_widen_even) (tree);
 378     tree (* builtin_mul_widen_odd) (tree);
 379   } vectorize;
 380
 381   /* The initial value of target_flags.  */
 382   int default_target_flags;
 383
 384   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
 385      passed to the switch; it is NULL if no argument was.  VALUE is the
 386      value of ARG if CODE specifies a UInteger option, otherwise it is
 387      1 if the positive form of the switch was used and 0 if the negative
 388      form was.  Return true if the switch was valid.  */
 389   bool (* handle_option) (size_t code, const char *arg, int value);
 390
 391   /* Return machine mode for filter value.  */
 392   enum machine_mode (* eh_return_filter_mode) (void);
 393
 394   /* Given two decls, merge their attributes and return the result.  */
 395   tree (* merge_decl_attributes) (tree, tree);
 396
 397   /* Given two types, merge their attributes and return the result.  */
 398   tree (* merge_type_attributes) (tree, tree);
 399
 400   /* Table of machine attributes and functions to handle them.
 401      Ignored if NULL.  */
 402   const struct attribute_spec *attribute_table;
 403
 404   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 405      one if they are compatible and two if they are nearly compatible
 406      (which causes a warning to be generated).  */
 407   int (* comp_type_attributes) (tree type1, tree type2);
 408
 409   /* Assign default attributes to the newly defined TYPE.  */
 410   void (* set_default_type_attributes) (tree type);
 411
 412   /* Insert attributes on the newly created DECL.  */
 413   void (* insert_attributes) (tree decl, tree *attributes);
 414
 415   /* Return true if FNDECL (which has at least one machine attribute)
 416      can be inlined despite its machine attributes, false otherwise.  */
 417   bool (* function_attribute_inlinable_p) (tree fndecl);
 418
 419   /* Return true if bitfields in RECORD_TYPE should follow the
 420      Microsoft Visual C++ bitfield layout rules.  */
 421   bool (* ms_bitfield_layout_p) (tree record_type);
 422
 423   /* True if the target supports decimal floating point.  */
 424   bool (* decimal_float_supported_p) (void);
 425
 426   /* Return true if anonymous bitfields affect structure alignment.  */
 427   bool (* align_anon_bitfield) (void);
 428
 429   /* Return true if volatile bitfields should use the narrowest type possible.
 430      Return false if they should use the container type.  */
 431   bool (* narrow_volatile_bitfield) (void);
 432
 433   /* Set up target-specific built-in functions.  */
 434   void (* init_builtins) (void);
 435
 436   /* Expand a target-specific builtin.  */
 437   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 438                           enum machine_mode mode, int ignore);
 439
 440   /* Select a replacement for a target-specific builtin.  This is done
 441      *before* regular type checking, and so allows the target to implement
 442      a crude form of function overloading.  The result is a complete
 443      expression that implements the operation.  */
 444   tree (*resolve_overloaded_builtin) (tree decl, tree params);
 445
 446   /* Fold a target-specific builtin.  */
 447   tree (* fold_builtin) (tree fndecl, tree arglist, bool ignore);
 448
 449   /* For a vendor-specific fundamental TYPE, return a pointer to
 450      a statically-allocated string containing the C++ mangling for
 451      TYPE.  In all other cases, return NULL.  */
 452   const char * (* mangle_fundamental_type) (tree type);
 453
 454   /* Make any adjustments to libfunc names needed for this target.  */
 455   void (* init_libfuncs) (void);
 456
 457   /* Given a decl, a section name, and whether the decl initializer
 458      has relocs, choose attributes for the section.  */
 459   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 460   unsigned int (* section_type_flags) (tree, const char *, int);
 461
 462   /* True if new jumps cannot be created, to replace existing ones or
 463      not, at the current point in the compilation.  */
 464   bool (* cannot_modify_jumps_p) (void);
 465
 466   /* Return a register class for which branch target register
 467      optimizations should be applied.  */
 468   int (* branch_target_register_class) (void);
 469
 470   /* Return true if branch target register optimizations should include
 471      callee-saved registers that are not already live during the current
 472      function.  AFTER_PE_GEN is true if prologues and epilogues have
 473      already been generated.  */
 474   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 475
 476   /* True if the constant X cannot be placed in the constant pool.  */
 477   bool (* cannot_force_const_mem) (rtx);
 478
 479   /* True if the insn X cannot be duplicated.  */
 480   bool (* cannot_copy_insn_p) (rtx);
 481
 482   /* True if X is considered to be commutative.  */
 483   bool (* commutative_p) (rtx, int);
 484
 485   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 486   rtx (* delegitimize_address) (rtx);
 487
 488   /* True if the given constant can be put into an object_block.  */
 489   bool (* use_blocks_for_constant_p) (enum machine_mode, rtx);
 490
 491   /* The minimum and maximum byte offsets for anchored addresses.  */
 492   HOST_WIDE_INT min_anchor_offset;
 493   HOST_WIDE_INT max_anchor_offset;
 494
 495   /* True if section anchors can be used to access the given symbol.  */
 496   bool (* use_anchors_for_symbol_p) (rtx);
 497
 498   /* True if it is OK to do sibling call optimization for the specified
 499      call expression EXP.  DECL will be the called function, or NULL if
 500      this is an indirect call.  */
 501   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 502
 503   /* True if EXP should be placed in a "small data" section.  */
 504   bool (* in_small_data_p) (tree);
 505
 506   /* True if EXP names an object for which name resolution must resolve
 507      to the current module.  */
 508   bool (* binds_local_p) (tree);
 509
 510   /* Do something target-specific to record properties of the DECL into
 511      the associated SYMBOL_REF.  */
 512   void (* encode_section_info) (tree, rtx, int);
 513
 514   /* Undo the effects of encode_section_info on the symbol string.  */
 515   const char * (* strip_name_encoding) (const char *);
 516
 517   /* If shift optabs for MODE are known to always truncate the shift count,
 518      return the mask that they apply.  Return 0 otherwise.  */
 519   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
 520
 521   /* Return the number of divisions in the given MODE that should be present,
 522      so that it is profitable to turn the division into a multiplication by
 523      the reciprocal.  */
 524   unsigned int (* min_divisions_for_recip_mul) (enum machine_mode mode);
 525
 526   /* If the representation of integral MODE is such that values are
 527      always sign-extended to a wider mode MODE_REP then return
 528      SIGN_EXTEND.  Return UNKNOWN otherwise.  */
 529   /* Note that the return type ought to be RTX_CODE, but that's not
 530      necessarily defined at this point.  */
 531   int (* mode_rep_extended) (enum machine_mode mode,
 532                              enum machine_mode mode_rep);
 533
 534   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 535   bool (* valid_pointer_mode) (enum machine_mode mode);
 536
 537   /* True if MODE is valid for the target.  By "valid", we mean able to
 538      be manipulated in non-trivial ways.  In particular, this means all
 539      the arithmetic is supported.  */
 540   bool (* scalar_mode_supported_p) (enum machine_mode mode);
 541
 542   /* Similarly for vector modes.  "Supported" here is less strict.  At
 543      least some operations are supported; need to check optabs or builtins
 544      for further details.  */
 545   bool (* vector_mode_supported_p) (enum machine_mode mode);
 546
 547   /* True if a vector is opaque.  */
 548   bool (* vector_opaque_p) (tree);
 549
 550   /* Compute a (partial) cost for rtx X.  Return true if the complete
 551      cost has been computed, and false if subexpressions should be
 552      scanned.  In either case, *TOTAL contains the cost result.  */
 553   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 554      not necessarily defined at this point.  */
 555   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 556
 557   /* Compute the cost of X, used as an address.  Never called with
 558      invalid addresses.  */
 559   int (* address_cost) (rtx x);
 560
 561   /* Return where to allocate pseudo for a given hard register initial
 562      value.  */
 563   rtx (* allocate_initial_value) (rtx x);
 564
 565   /* Given a register, this hook should return a parallel of registers
 566      to represent where to find the register pieces.  Define this hook
 567      if the register and its mode are represented in Dwarf in
 568      non-contiguous locations, or if the register should be
 569      represented in more than one register in Dwarf.  Otherwise, this
 570      hook should return NULL_RTX.  */
 571   rtx (* dwarf_register_span) (rtx);
 572
 573   /* Fetch the fixed register(s) which hold condition codes, for
 574      targets where it makes sense to look for duplicate assignments to
 575      the condition codes.  This should return true if there is such a
 576      register, false otherwise.  The arguments should be set to the
 577      fixed register numbers.  Up to two condition code registers are
 578      supported.  If there is only one for this target, the int pointed
 579      at by the second argument should be set to -1.  */
 580   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 581
 582   /* If two condition code modes are compatible, return a condition
 583      code mode which is compatible with both, such that a comparison
 584      done in the returned mode will work for both of the original
 585      modes.  If the condition code modes are not compatible, return
 586      VOIDmode.  */
 587   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 588                                              enum machine_mode);
 589
 590   /* Do machine-dependent code transformations.  Called just before
 591      delayed-branch scheduling.  */
 592   void (* machine_dependent_reorg) (void);
 593
 594   /* Create the __builtin_va_list type.  */
 595   tree (* build_builtin_va_list) (void);
 596
 597   /* Gimplifies a VA_ARG_EXPR.  */
 598   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 599                                  tree *post_p);
 600
 601   /* Validity-checking routines for PCH files, target-specific.
 602      get_pch_validity returns a pointer to the data to be stored,
 603      and stores the size in its argument.  pch_valid_p gets the same
 604      information back and returns NULL if the PCH is valid,
 605      or an error message if not.
 606   */
 607   void * (* get_pch_validity) (size_t *);
 608   const char * (* pch_valid_p) (const void *, size_t);
 609
 610   /* If nonnull, this function checks whether a PCH file with the
 611      given set of target flags can be used.  It returns NULL if so,
 612      otherwise it returns an error message.  */
 613   const char *(*check_pch_target_flags) (int);
 614
 615   /* True if the compiler should give an enum type only as many
 616      bytes as it takes to represent the range of possible values of
 617      that type.  */
 618   bool (* default_short_enums) (void);
 619
 620   /* This target hook returns an rtx that is used to store the address
 621      of the current frame into the built-in setjmp buffer.  */
 622   rtx (* builtin_setjmp_frame_value) (void);
 623
 624   /* This target hook should add STRING_CST trees for any hard regs
 625      the port wishes to automatically clobber for an asm.  */
 626   tree (* md_asm_clobbers) (tree, tree, tree);
 627
 628   /* This target hook allows the backend to specify a calling convention
 629      in the debug information.  This function actually returns an
 630      enum dwarf_calling_convention, but because of forward declarations
 631      and not wanting to include dwarf2.h everywhere target.h is included
 632      the function is being declared as an int.  */
 633   int (* dwarf_calling_convention) (tree);
 634
 635   /* This target hook allows the backend to emit frame-related insns that
 636      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
 637      engine will invoke it on insns of the form
 638        (set (reg) (unspec [...] UNSPEC_INDEX))
 639      and
 640        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
 641      to let the backend emit the call frame instructions.  */
 642   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
 643
 644   /* Perform architecture specific checking of statements gimplified
 645      from VA_ARG_EXPR.  LHS is left hand side of MODIFY_EXPR, RHS
 646      is right hand side.  Returns true if the statements doesn't need
 647      to be checked for va_list references.  */
 648   bool (* stdarg_optimize_hook) (struct stdarg_info *ai, tree lhs, tree rhs);
 649
 650   /* This target hook allows the operating system to override the DECL
 651      that represents the external variable that contains the stack
 652      protection guard variable.  The type of this DECL is ptr_type_node.  */
 653   tree (* stack_protect_guard) (void);
 654
 655   /* This target hook allows the operating system to override the CALL_EXPR
 656      that is invoked when a check vs the guard variable fails.  */
 657   tree (* stack_protect_fail) (void);
 658
 659   /* Returns NULL if target supports the insn within a doloop block,
 660      otherwise it returns an error message.  */
 661   const char * (*invalid_within_doloop) (rtx);
 662
 663   /* DECL is a variable or function with __attribute__((dllimport))
 664      specified.  Use this hook if the target needs to add extra validation
 665      checks to  handle_dll_attribute ().  */
 666   bool (* valid_dllimport_attribute_p) (tree decl);
 667
 668   /* Functions relating to calls - argument passing, returns, etc.  */
 669   struct calls {
 670     bool (*promote_function_args) (tree fntype);
 671     bool (*promote_function_return) (tree fntype);
 672     bool (*promote_prototypes) (tree fntype);
 673     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 674     bool (*return_in_memory) (tree type, tree fndecl);
 675     bool (*return_in_msb) (tree type);
 676
 677     /* Return true if a parameter must be passed by reference.  TYPE may
 678        be null if this is a libcall.  CA may be null if this query is
 679        from __builtin_va_arg.  */
 680     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 681                                tree type, bool named_arg);
 682
 683     rtx (*expand_builtin_saveregs) (void);
 684     /* Returns pretend_argument_size.  */
 685     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 686                                     tree type, int *pretend_arg_size,
 687                                     int second_time);
 688     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 689     /* Returns true if we should use
 690        targetm.calls.setup_incoming_varargs() and/or
 691        targetm.calls.strict_argument_naming().  */
 692     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 693
 694     /* Given a complex type T, return true if a parameter of type T
 695        should be passed as two scalars.  */
 696     bool (* split_complex_arg) (tree type);
 697
 698     /* Return true if type T, mode MODE, may not be passed in registers,
 699        but must be passed on the stack.  */
 700     /* ??? This predicate should be applied strictly after pass-by-reference.
 701        Need audit to verify that this is the case.  */
 702     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 703
 704     /* Return true if type TYPE, mode MODE, which is passed by reference,
 705        should have the object copy generated by the callee rather than
 706        the caller.  It is never called for TYPE requiring constructors.  */
 707     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 708                             tree type, bool named);
 709
 710     /* Return zero for arguments passed entirely on the stack or entirely
 711        in registers.  If passed in both, return the number of bytes passed
 712        in registers; the balance is therefore passed on the stack.  */
 713     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 714                                tree type, bool named);
 715
 716     /* Return the diagnostic message string if function without a prototype
 717        is not allowed for this 'val' argument; NULL otherwise. */
 718     const char *(*invalid_arg_for_unprototyped_fn) (tree typelist,
 719                                                     tree funcdecl, tree val);
 720
 721     /* Return an rtx for the return value location of the function
 722        specified by FN_DECL_OR_TYPE with a return type of RET_TYPE.  */
 723     rtx (*function_value) (tree ret_type, tree fn_decl_or_type,
 724                            bool outgoing);
 725
 726     /* Return an rtx for the argument pointer incoming to the
 727        current function.  */
 728     rtx (*internal_arg_pointer) (void);
 729   } calls;
 730
 731   /* Return the diagnostic message string if conversion from FROMTYPE
 732      to TOTYPE is not allowed, NULL otherwise.  */
 733   const char *(*invalid_conversion) (tree fromtype, tree totype);
 734
 735   /* Return the diagnostic message string if the unary operation OP is
 736      not permitted on TYPE, NULL otherwise.  */
 737   const char *(*invalid_unary_op) (int op, tree type);
 738
 739   /* Return the diagnostic message string if the binary operation OP
 740      is not permitted on TYPE1 and TYPE2, NULL otherwise.  */
 741   const char *(*invalid_binary_op) (int op, tree type1, tree type2);
 742
 743   /* Return the class for a secondary reload, and fill in extra information.  */
 744   enum reg_class (*secondary_reload) (bool, rtx, enum reg_class,
 745                                       enum machine_mode,
 746                                       struct secondary_reload_info *);
 747
 748   /* Functions specific to the C++ frontend.  */
 749   struct cxx {
 750     /* Return the integer type used for guard variables.  */
 751     tree (*guard_type) (void);
 752     /* Return true if only the low bit of the guard should be tested.  */
 753     bool (*guard_mask_bit) (void);
 754     /* Returns the size of the array cookie for an array of type.  */
 755     tree (*get_cookie_size) (tree);
 756     /* Returns true if the element size should be stored in the
 757        array cookie.  */
 758     bool (*cookie_has_size) (void);
 759     /* Allows backends to perform additional processing when
 760        deciding if a class should be exported or imported.  */
 761     int (*import_export_class) (tree, int);
 762     /* Returns true if constructors and destructors return "this".  */
 763     bool (*cdtor_returns_this) (void);
 764     /* Returns true if the key method for a class can be an inline
 765        function, so long as it is not declared inline in the class
 766        itself.  Returning true is the behavior required by the Itanium
 767        C++ ABI.  */
 768     bool (*key_method_may_be_inline) (void);
 769     /* DECL is a virtual table, virtual table table, typeinfo object,
 770        or other similar implicit class data object that will be
 771        emitted with external linkage in this translation unit.  No ELF
 772        visibility has been explicitly specified.  If the target needs
 773        to specify a visibility other than that of the containing class,
 774        use this hook to set DECL_VISIBILITY and
 775        DECL_VISIBILITY_SPECIFIED.  */
 776     void (*determine_class_data_visibility) (tree decl);
 777     /* Returns true (the default) if virtual tables and other
 778        similar implicit class data objects are always COMDAT if they
 779        have external linkage.  If this hook returns false, then
 780        class data for classes whose virtual table will be emitted in
 781        only one translation unit will not be COMDAT.  */
 782     bool (*class_data_always_comdat) (void);
 783     /* Returns true if __aeabi_atexit should be used to register static
 784        destructors.  */
 785     bool (*use_aeabi_atexit) (void);
 786     /* Returns true if target may use atexit in the same manner as
 787     __cxa_atexit  to register static destructors.  */
 788     bool (*use_atexit_for_cxa_atexit) (void);
 789     /* TYPE is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that
 790        has just been defined.  Use this hook to make adjustments to the
 791        class  (eg, tweak visibility or perform any other required
 792        target modifications).  */
 793     void (*adjust_class_at_definition) (tree type);
 794   } cxx;
 795
 796   /* For targets that need to mark extra registers as live on entry to
 797      the function, they should define this target hook and set their
 798      bits in the bitmap passed in. */
 799   void (*live_on_entry) (bitmap);
 800
 801   /* True if unwinding tables should be generated by default.  */
 802   bool unwind_tables_default;
 803
 804   /* Leave the boolean fields at the end.  */
 805
 806   /* True if arbitrary sections are supported.  */
 807   bool have_named_sections;
 808
 809   /* True if we can create zeroed data by switching to a BSS section
 810      and then using ASM_OUTPUT_SKIP to allocate the space.  */
 811   bool have_switchable_bss_sections;
 812
 813   /* True if "native" constructors and destructors are supported,
 814      false if we're using collect2 for the job.  */
 815   bool have_ctors_dtors;
 816
 817   /* True if thread-local storage is supported.  */
 818   bool have_tls;
 819
 820   /* True if a small readonly data section is supported.  */
 821   bool have_srodata_section;
 822
 823   /* True if EH frame info sections should be zero-terminated.  */
 824   bool terminate_dw2_eh_frame_info;
 825
 826   /* True if #NO_APP should be emitted at the beginning of
 827      assembly output.  */
 828   bool file_start_app_off;
 829
 830   /* True if output_file_directive should be called for main_input_filename
 831      at the beginning of assembly output.  */
 832   bool file_start_file_directive;
 833
 834   /* True if #pragma redefine_extname is to be supported.  */
 835   bool handle_pragma_redefine_extname;
 836
 837   /* True if #pragma extern_prefix is to be supported.  */
 838   bool handle_pragma_extern_prefix;
 839
 840   /* True if the target is allowed to reorder memory accesses unless
 841      synchronization is explicitly requested.  */
 842   bool relaxed_ordering;
 843
 844   /* Returns true if we should generate exception tables for use with the
 845      ARM EABI.  The effects the encoding of function exception specifications.
 846    */
 847   bool arm_eabi_unwinder;
 848
 849   /* Leave the boolean fields at the end.  */
 850 };
 851
 852 extern struct gcc_target targetm;
 853
 854 #endif /* GCC_TARGET_H */