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