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   } vectorize;
 373
 374   /* The initial value of target_flags.  */
 375   int default_target_flags;
 376
 377   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
 378      passed to the switch; it is NULL if no argument was.  VALUE is the
 379      value of ARG if CODE specifies a UInteger option, otherwise it is
 380      1 if the positive form of the switch was used and 0 if the negative
 381      form was.  Return true if the switch was valid.  */
 382   bool (* handle_option) (size_t code, const char *arg, int value);
 383
 384   /* Return machine mode for filter value.  */
 385   enum machine_mode (* eh_return_filter_mode) (void);
 386
 387   /* Given two decls, merge their attributes and return the result.  */
 388   tree (* merge_decl_attributes) (tree, tree);
 389
 390   /* Given two types, merge their attributes and return the result.  */
 391   tree (* merge_type_attributes) (tree, tree);
 392
 393   /* Table of machine attributes and functions to handle them.
 394      Ignored if NULL.  */
 395   const struct attribute_spec *attribute_table;
 396
 397   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 398      one if they are compatible and two if they are nearly compatible
 399      (which causes a warning to be generated).  */
 400   int (* comp_type_attributes) (tree type1, tree type2);
 401
 402   /* Assign default attributes to the newly defined TYPE.  */
 403   void (* set_default_type_attributes) (tree type);
 404
 405   /* Insert attributes on the newly created DECL.  */
 406   void (* insert_attributes) (tree decl, tree *attributes);
 407
 408   /* Return true if FNDECL (which has at least one machine attribute)
 409      can be inlined despite its machine attributes, false otherwise.  */
 410   bool (* function_attribute_inlinable_p) (tree fndecl);
 411
 412   /* Return true if bitfields in RECORD_TYPE should follow the
 413      Microsoft Visual C++ bitfield layout rules.  */
 414   bool (* ms_bitfield_layout_p) (tree record_type);
 415
 416   /* True if the target supports decimal floating point.  */
 417   bool (* decimal_float_supported_p) (void);
 418
 419   /* Return true if anonymous bitfields affect structure alignment.  */
 420   bool (* align_anon_bitfield) (void);
 421
 422   /* Return true if volatile bitfields should use the narrowest type possible.
 423      Return false if they should use the container type.  */
 424   bool (* narrow_volatile_bitfield) (void);
 425
 426   /* Set up target-specific built-in functions.  */
 427   void (* init_builtins) (void);
 428
 429   /* Expand a target-specific builtin.  */
 430   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 431                           enum machine_mode mode, int ignore);
 432
 433   /* Select a replacement for a target-specific builtin.  This is done
 434      *before* regular type checking, and so allows the target to implement
 435      a crude form of function overloading.  The result is a complete
 436      expression that implements the operation.  */
 437   tree (*resolve_overloaded_builtin) (tree decl, tree params);
 438
 439   /* Fold a target-specific builtin.  */
 440   tree (* fold_builtin) (tree fndecl, tree arglist, bool ignore);
 441
 442   /* For a vendor-specific fundamental TYPE, return a pointer to
 443      a statically-allocated string containing the C++ mangling for
 444      TYPE.  In all other cases, return NULL.  */
 445   const char * (* mangle_fundamental_type) (tree type);
 446
 447   /* Make any adjustments to libfunc names needed for this target.  */
 448   void (* init_libfuncs) (void);
 449
 450   /* Given a decl, a section name, and whether the decl initializer
 451      has relocs, choose attributes for the section.  */
 452   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 453   unsigned int (* section_type_flags) (tree, const char *, int);
 454
 455   /* True if new jumps cannot be created, to replace existing ones or
 456      not, at the current point in the compilation.  */
 457   bool (* cannot_modify_jumps_p) (void);
 458
 459   /* Return a register class for which branch target register
 460      optimizations should be applied.  */
 461   int (* branch_target_register_class) (void);
 462
 463   /* Return true if branch target register optimizations should include
 464      callee-saved registers that are not already live during the current
 465      function.  AFTER_PE_GEN is true if prologues and epilogues have
 466      already been generated.  */
 467   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 468
 469   /* True if the constant X cannot be placed in the constant pool.  */
 470   bool (* cannot_force_const_mem) (rtx);
 471
 472   /* True if the insn X cannot be duplicated.  */
 473   bool (* cannot_copy_insn_p) (rtx);
 474
 475   /* True if X is considered to be commutative.  */
 476   bool (* commutative_p) (rtx, int);
 477
 478   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 479   rtx (* delegitimize_address) (rtx);
 480
 481   /* True if the given constant can be put into an object_block.  */
 482   bool (* use_blocks_for_constant_p) (enum machine_mode, rtx);
 483
 484   /* The minimum and maximum byte offsets for anchored addresses.  */
 485   HOST_WIDE_INT min_anchor_offset;
 486   HOST_WIDE_INT max_anchor_offset;
 487
 488   /* True if section anchors can be used to access the given symbol.  */
 489   bool (* use_anchors_for_symbol_p) (rtx);
 490
 491   /* True if it is OK to do sibling call optimization for the specified
 492      call expression EXP.  DECL will be the called function, or NULL if
 493      this is an indirect call.  */
 494   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 495
 496   /* True if EXP should be placed in a "small data" section.  */
 497   bool (* in_small_data_p) (tree);
 498
 499   /* True if EXP names an object for which name resolution must resolve
 500      to the current module.  */
 501   bool (* binds_local_p) (tree);
 502
 503   /* Do something target-specific to record properties of the DECL into
 504      the associated SYMBOL_REF.  */
 505   void (* encode_section_info) (tree, rtx, int);
 506
 507   /* Undo the effects of encode_section_info on the symbol string.  */
 508   const char * (* strip_name_encoding) (const char *);
 509
 510   /* If shift optabs for MODE are known to always truncate the shift count,
 511      return the mask that they apply.  Return 0 otherwise.  */
 512   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
 513
 514   /* Return the number of divisions in the given MODE that should be present,
 515      so that it is profitable to turn the division into a multiplication by
 516      the reciprocal.  */
 517   unsigned int (* min_divisions_for_recip_mul) (enum machine_mode mode);
 518
 519   /* If the representation of integral MODE is such that values are
 520      always sign-extended to a wider mode MODE_REP then return
 521      SIGN_EXTEND.  Return UNKNOWN otherwise.  */
 522   /* Note that the return type ought to be RTX_CODE, but that's not
 523      necessarily defined at this point.  */
 524   int (* mode_rep_extended) (enum machine_mode mode,
 525                              enum machine_mode mode_rep);
 526
 527   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 528   bool (* valid_pointer_mode) (enum machine_mode mode);
 529
 530   /* True if MODE is valid for the target.  By "valid", we mean able to
 531      be manipulated in non-trivial ways.  In particular, this means all
 532      the arithmetic is supported.  */
 533   bool (* scalar_mode_supported_p) (enum machine_mode mode);
 534
 535   /* Similarly for vector modes.  "Supported" here is less strict.  At
 536      least some operations are supported; need to check optabs or builtins
 537      for further details.  */
 538   bool (* vector_mode_supported_p) (enum machine_mode mode);
 539
 540   /* True if a vector is opaque.  */
 541   bool (* vector_opaque_p) (tree);
 542
 543   /* Compute a (partial) cost for rtx X.  Return true if the complete
 544      cost has been computed, and false if subexpressions should be
 545      scanned.  In either case, *TOTAL contains the cost result.  */
 546   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 547      not necessarily defined at this point.  */
 548   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 549
 550   /* Compute the cost of X, used as an address.  Never called with
 551      invalid addresses.  */
 552   int (* address_cost) (rtx x);
 553
 554   /* Return where to allocate pseudo for a given hard register initial
 555      value.  */
 556   rtx (* allocate_initial_value) (rtx x);
 557
 558   /* Given a register, this hook should return a parallel of registers
 559      to represent where to find the register pieces.  Define this hook
 560      if the register and its mode are represented in Dwarf in
 561      non-contiguous locations, or if the register should be
 562      represented in more than one register in Dwarf.  Otherwise, this
 563      hook should return NULL_RTX.  */
 564   rtx (* dwarf_register_span) (rtx);
 565
 566   /* Fetch the fixed register(s) which hold condition codes, for
 567      targets where it makes sense to look for duplicate assignments to
 568      the condition codes.  This should return true if there is such a
 569      register, false otherwise.  The arguments should be set to the
 570      fixed register numbers.  Up to two condition code registers are
 571      supported.  If there is only one for this target, the int pointed
 572      at by the second argument should be set to -1.  */
 573   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 574
 575   /* If two condition code modes are compatible, return a condition
 576      code mode which is compatible with both, such that a comparison
 577      done in the returned mode will work for both of the original
 578      modes.  If the condition code modes are not compatible, return
 579      VOIDmode.  */
 580   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 581                                              enum machine_mode);
 582
 583   /* Do machine-dependent code transformations.  Called just before
 584      delayed-branch scheduling.  */
 585   void (* machine_dependent_reorg) (void);
 586
 587   /* Create the __builtin_va_list type.  */
 588   tree (* build_builtin_va_list) (void);
 589
 590   /* Gimplifies a VA_ARG_EXPR.  */
 591   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 592                                  tree *post_p);
 593
 594   /* Validity-checking routines for PCH files, target-specific.
 595      get_pch_validity returns a pointer to the data to be stored,
 596      and stores the size in its argument.  pch_valid_p gets the same
 597      information back and returns NULL if the PCH is valid,
 598      or an error message if not.
 599   */
 600   void * (* get_pch_validity) (size_t *);
 601   const char * (* pch_valid_p) (const void *, size_t);
 602
 603   /* If nonnull, this function checks whether a PCH file with the
 604      given set of target flags can be used.  It returns NULL if so,
 605      otherwise it returns an error message.  */
 606   const char *(*check_pch_target_flags) (int);
 607
 608   /* True if the compiler should give an enum type only as many
 609      bytes as it takes to represent the range of possible values of
 610      that type.  */
 611   bool (* default_short_enums) (void);
 612
 613   /* This target hook returns an rtx that is used to store the address
 614      of the current frame into the built-in setjmp buffer.  */
 615   rtx (* builtin_setjmp_frame_value) (void);
 616
 617   /* This target hook should add STRING_CST trees for any hard regs
 618      the port wishes to automatically clobber for an asm.  */
 619   tree (* md_asm_clobbers) (tree, tree, tree);
 620
 621   /* This target hook allows the backend to specify a calling convention
 622      in the debug information.  This function actually returns an
 623      enum dwarf_calling_convention, but because of forward declarations
 624      and not wanting to include dwarf2.h everywhere target.h is included
 625      the function is being declared as an int.  */
 626   int (* dwarf_calling_convention) (tree);
 627
 628   /* This target hook allows the backend to emit frame-related insns that
 629      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
 630      engine will invoke it on insns of the form
 631        (set (reg) (unspec [...] UNSPEC_INDEX))
 632      and
 633        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
 634      to let the backend emit the call frame instructions.  */
 635   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
 636
 637   /* Perform architecture specific checking of statements gimplified
 638      from VA_ARG_EXPR.  LHS is left hand side of MODIFY_EXPR, RHS
 639      is right hand side.  Returns true if the statements doesn't need
 640      to be checked for va_list references.  */
 641   bool (* stdarg_optimize_hook) (struct stdarg_info *ai, tree lhs, tree rhs);
 642
 643   /* This target hook allows the operating system to override the DECL
 644      that represents the external variable that contains the stack
 645      protection guard variable.  The type of this DECL is ptr_type_node.  */
 646   tree (* stack_protect_guard) (void);
 647
 648   /* This target hook allows the operating system to override the CALL_EXPR
 649      that is invoked when a check vs the guard variable fails.  */
 650   tree (* stack_protect_fail) (void);
 651
 652   /* Returns NULL if target supports the insn within a doloop block,
 653      otherwise it returns an error message.  */
 654   const char * (*invalid_within_doloop) (rtx);
 655
 656   /* DECL is a variable or function with __attribute__((dllimport))
 657      specified.  Use this hook if the target needs to add extra validation
 658      checks to  handle_dll_attribute ().  */
 659   bool (* valid_dllimport_attribute_p) (tree decl);
 660
 661   /* Functions relating to calls - argument passing, returns, etc.  */
 662   struct calls {
 663     bool (*promote_function_args) (tree fntype);
 664     bool (*promote_function_return) (tree fntype);
 665     bool (*promote_prototypes) (tree fntype);
 666     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 667     bool (*return_in_memory) (tree type, tree fndecl);
 668     bool (*return_in_msb) (tree type);
 669
 670     /* Return true if a parameter must be passed by reference.  TYPE may
 671        be null if this is a libcall.  CA may be null if this query is
 672        from __builtin_va_arg.  */
 673     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 674                                tree type, bool named_arg);
 675
 676     rtx (*expand_builtin_saveregs) (void);
 677     /* Returns pretend_argument_size.  */
 678     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 679                                     tree type, int *pretend_arg_size,
 680                                     int second_time);
 681     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 682     /* Returns true if we should use
 683        targetm.calls.setup_incoming_varargs() and/or
 684        targetm.calls.strict_argument_naming().  */
 685     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 686
 687     /* Given a complex type T, return true if a parameter of type T
 688        should be passed as two scalars.  */
 689     bool (* split_complex_arg) (tree type);
 690
 691     /* Return true if type T, mode MODE, may not be passed in registers,
 692        but must be passed on the stack.  */
 693     /* ??? This predicate should be applied strictly after pass-by-reference.
 694        Need audit to verify that this is the case.  */
 695     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 696
 697     /* Return true if type TYPE, mode MODE, which is passed by reference,
 698        should have the object copy generated by the callee rather than
 699        the caller.  It is never called for TYPE requiring constructors.  */
 700     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 701                             tree type, bool named);
 702
 703     /* Return zero for arguments passed entirely on the stack or entirely
 704        in registers.  If passed in both, return the number of bytes passed
 705        in registers; the balance is therefore passed on the stack.  */
 706     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 707                                tree type, bool named);
 708
 709     /* Return the diagnostic message string if function without a prototype
 710        is not allowed for this 'val' argument; NULL otherwise. */
 711     const char *(*invalid_arg_for_unprototyped_fn) (tree typelist,
 712                                                     tree funcdecl, tree val);
 713
 714     /* Return an rtx for the return value location of the function
 715        specified by FN_DECL_OR_TYPE with a return type of RET_TYPE.  */
 716     rtx (*function_value) (tree ret_type, tree fn_decl_or_type,
 717                            bool outgoing);
 718
 719     /* Return an rtx for the argument pointer incoming to the
 720        current function.  */
 721     rtx (*internal_arg_pointer) (void);
 722   } calls;
 723
 724   /* Return the diagnostic message string if conversion from FROMTYPE
 725      to TOTYPE is not allowed, NULL otherwise.  */
 726   const char *(*invalid_conversion) (tree fromtype, tree totype);
 727
 728   /* Return the diagnostic message string if the unary operation OP is
 729      not permitted on TYPE, NULL otherwise.  */
 730   const char *(*invalid_unary_op) (int op, tree type);
 731
 732   /* Return the diagnostic message string if the binary operation OP
 733      is not permitted on TYPE1 and TYPE2, NULL otherwise.  */
 734   const char *(*invalid_binary_op) (int op, tree type1, tree type2);
 735
 736   /* Return the class for a secondary reload, and fill in extra information.  */
 737   enum reg_class (*secondary_reload) (bool, rtx, enum reg_class,
 738                                       enum machine_mode,
 739                                       struct secondary_reload_info *);
 740
 741   /* Functions specific to the C++ frontend.  */
 742   struct cxx {
 743     /* Return the integer type used for guard variables.  */
 744     tree (*guard_type) (void);
 745     /* Return true if only the low bit of the guard should be tested.  */
 746     bool (*guard_mask_bit) (void);
 747     /* Returns the size of the array cookie for an array of type.  */
 748     tree (*get_cookie_size) (tree);
 749     /* Returns true if the element size should be stored in the
 750        array cookie.  */
 751     bool (*cookie_has_size) (void);
 752     /* Allows backends to perform additional processing when
 753        deciding if a class should be exported or imported.  */
 754     int (*import_export_class) (tree, int);
 755     /* Returns true if constructors and destructors return "this".  */
 756     bool (*cdtor_returns_this) (void);
 757     /* Returns true if the key method for a class can be an inline
 758        function, so long as it is not declared inline in the class
 759        itself.  Returning true is the behavior required by the Itanium
 760        C++ ABI.  */
 761     bool (*key_method_may_be_inline) (void);
 762     /* DECL is a virtual table, virtual table table, typeinfo object,
 763        or other similar implicit class data object that will be
 764        emitted with external linkage in this translation unit.  No ELF
 765        visibility has been explicitly specified.  If the target needs
 766        to specify a visibility other than that of the containing class,
 767        use this hook to set DECL_VISIBILITY and
 768        DECL_VISIBILITY_SPECIFIED.  */
 769     void (*determine_class_data_visibility) (tree decl);
 770     /* Returns true (the default) if virtual tables and other
 771        similar implicit class data objects are always COMDAT if they
 772        have external linkage.  If this hook returns false, then
 773        class data for classes whose virtual table will be emitted in
 774        only one translation unit will not be COMDAT.  */
 775     bool (*class_data_always_comdat) (void);
 776     /* Returns true if __aeabi_atexit should be used to register static
 777        destructors.  */
 778     bool (*use_aeabi_atexit) (void);
 779     /* TYPE is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that
 780        has just been defined.  Use this hook to make adjustments to the
 781        class  (eg, tweak visibility or perform any other required
 782        target modifications).  */
 783     void (*adjust_class_at_definition) (tree type);
 784   } cxx;
 785
 786   /* For targets that need to mark extra registers as live on entry to
 787      the function, they should define this target hook and set their
 788      bits in the bitmap passed in. */
 789   void (*live_on_entry) (bitmap);
 790
 791   /* True if unwinding tables should be generated by default.  */
 792   bool unwind_tables_default;
 793
 794   /* Leave the boolean fields at the end.  */
 795
 796   /* True if arbitrary sections are supported.  */
 797   bool have_named_sections;
 798
 799   /* True if we can create zeroed data by switching to a BSS section
 800      and then using ASM_OUTPUT_SKIP to allocate the space.  */
 801   bool have_switchable_bss_sections;
 802
 803   /* True if "native" constructors and destructors are supported,
 804      false if we're using collect2 for the job.  */
 805   bool have_ctors_dtors;
 806
 807   /* True if thread-local storage is supported.  */
 808   bool have_tls;
 809
 810   /* True if a small readonly data section is supported.  */
 811   bool have_srodata_section;
 812
 813   /* True if EH frame info sections should be zero-terminated.  */
 814   bool terminate_dw2_eh_frame_info;
 815
 816   /* True if #NO_APP should be emitted at the beginning of
 817      assembly output.  */
 818   bool file_start_app_off;
 819
 820   /* True if output_file_directive should be called for main_input_filename
 821      at the beginning of assembly output.  */
 822   bool file_start_file_directive;
 823
 824   /* True if #pragma redefine_extname is to be supported.  */
 825   bool handle_pragma_redefine_extname;
 826
 827   /* True if #pragma extern_prefix is to be supported.  */
 828   bool handle_pragma_extern_prefix;
 829
 830   /* True if the target is allowed to reorder memory accesses unless
 831      synchronization is explicitly requested.  */
 832   bool relaxed_ordering;
 833
 834   /* Returns true if we should generate exception tables for use with the
 835      ARM EABI.  The effects the encoding of function exception specifications.
 836    */
 837   bool arm_eabi_unwinder;
 838
 839   /* Leave the boolean fields at the end.  */
 840 };
 841
 842 extern struct gcc_target targetm;
 843
 844 #endif /* GCC_TARGET_H */