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 /* Types used by the record_gcc_switches() target function.  */
  55 typedef enum
  56 {
  57   SWITCH_TYPE_PASSED,           /* A switch passed on the command line.  */
  58   SWITCH_TYPE_ENABLED,          /* An option that is currently enabled.  */
  59   SWITCH_TYPE_DESCRIPTIVE,      /* Descriptive text, not a switch or option.  */
  60   SWITCH_TYPE_LINE_START,       /* Please emit any necessary text at the start of a line.  */
  61   SWITCH_TYPE_LINE_END          /* Please emit a line terminator.  */
  62 }
  63 print_switch_type;
  64
  65 typedef int (* print_switch_fn_type) (print_switch_type, const char *);
  66
  67 /* An example implementation for ELF targets.  Defined in varasm.c  */
  68 extern int elf_record_gcc_switches (print_switch_type type, const char *);
  69
  70 struct stdarg_info;
  71 struct spec_info_def;
  72
  73 /* The struct used by the secondary_reload target hook.  */
  74 typedef struct secondary_reload_info
  75 {
  76   /* icode is actually an enum insn_code, but we don't want to force every
  77      file that includes target.h to include optabs.h .  */
  78   int icode;
  79   int extra_cost; /* Cost for using (a) scratch register(s) to be taken
  80                      into account by copy_cost.  */
  81   /* The next two members are for the use of the backward
  82      compatibility hook.  */
  83   struct secondary_reload_info *prev_sri;
  84   int t_icode; /* Actually an enum insn_code - see above.  */
  85 } secondary_reload_info;
  86
  87 /* This is defined in sched-int.h .  */
  88 struct _dep;
  89
  90 struct gcc_target
  91 {
  92   /* Functions that output assembler for the target.  */
  93   struct asm_out
  94   {
  95     /* Opening and closing parentheses for asm expression grouping.  */
  96     const char *open_paren, *close_paren;
  97
  98     /* Assembler instructions for creating various kinds of integer object.  */
  99     const char *byte_op;
 100     struct asm_int_op
 101     {
 102       const char *hi;
 103       const char *si;
 104       const char *di;
 105       const char *ti;
 106     } aligned_op, unaligned_op;
 107
 108     /* Try to output the assembler code for an integer object whose
 109        value is given by X.  SIZE is the size of the object in bytes and
 110        ALIGNED_P indicates whether it is aligned.  Return true if
 111        successful.  Only handles cases for which BYTE_OP, ALIGNED_OP
 112        and UNALIGNED_OP are NULL.  */
 113     bool (* integer) (rtx x, unsigned int size, int aligned_p);
 114
 115     /* Output code that will globalize a label.  */
 116     void (* globalize_label) (FILE *, const char *);
 117
 118     /* Output code that will globalize a declaration.  */
 119     void (* globalize_decl_name) (FILE *, tree);
 120
 121     /* Output code that will emit a label for unwind info, if this
 122        target requires such labels.  Second argument is the decl the
 123        unwind info is associated with, third is a boolean: true if
 124        this is for exception handling, fourth is a boolean: true if
 125        this is only a placeholder for an omitted FDE.  */
 126     void (* unwind_label) (FILE *, tree, int, int);
 127
 128     /* Output code that will emit a label to divide up the exception
 129        table.  */
 130     void (* except_table_label) (FILE *);
 131
 132     /* Emit any directives required to unwind this instruction.  */
 133     void (* unwind_emit) (FILE *, rtx);
 134
 135     /* Output an internal label.  */
 136     void (* internal_label) (FILE *, const char *, unsigned long);
 137
 138     /* Emit a ttype table reference to a typeinfo object.  */
 139     bool (* ttype) (rtx);
 140
 141     /* Emit an assembler directive to set visibility for the symbol
 142        associated with the tree decl.  */
 143     void (* visibility) (tree, int);
 144
 145     /* Output the assembler code for entry to a function.  */
 146     void (* function_prologue) (FILE *, HOST_WIDE_INT);
 147
 148     /* Output the assembler code for end of prologue.  */
 149     void (* function_end_prologue) (FILE *);
 150
 151     /* Output the assembler code for start of epilogue.  */
 152     void (* function_begin_epilogue) (FILE *);
 153
 154     /* Output the assembler code for function exit.  */
 155     void (* function_epilogue) (FILE *, HOST_WIDE_INT);
 156
 157     /* Initialize target-specific sections.  */
 158     void (* init_sections) (void);
 159
 160     /* Tell assembler to change to section NAME with attributes FLAGS.
 161        If DECL is non-NULL, it is the VAR_DECL or FUNCTION_DECL with
 162        which this section is associated.  */
 163     void (* named_section) (const char *name, unsigned int flags, tree decl);
 164
 165     /* Return a section for EXP.  It may be a DECL or a constant.  RELOC
 166        is nonzero if runtime relocations must be applied; bit 1 will be
 167        set if the runtime relocations require non-local name resolution.
 168        ALIGN is the required alignment of the data.  */
 169     section *(* select_section) (tree, int, unsigned HOST_WIDE_INT);
 170
 171     /* Return a section for X.  MODE is X's mode and ALIGN is its
 172        alignment in bits.  */
 173     section *(* select_rtx_section) (enum machine_mode, rtx,
 174                                      unsigned HOST_WIDE_INT);
 175
 176     /* Select a unique section name for DECL.  RELOC is the same as
 177        for SELECT_SECTION.  */
 178     void (* unique_section) (tree, int);
 179
 180     /* Return the readonly data section associated with function DECL.  */
 181     section *(* function_rodata_section) (tree);
 182
 183     /* Output a constructor for a symbol with a given priority.  */
 184     void (* constructor) (rtx, int);
 185
 186     /* Output a destructor for a symbol with a given priority.  */
 187     void (* destructor) (rtx, int);
 188
 189     /* Output the assembler code for a thunk function.  THUNK_DECL is the
 190        declaration for the thunk function itself, FUNCTION is the decl for
 191        the target function.  DELTA is an immediate constant offset to be
 192        added to THIS.  If VCALL_OFFSET is nonzero, the word at
 193        *(*this + vcall_offset) should be added to THIS.  */
 194     void (* output_mi_thunk) (FILE *file, tree thunk_decl,
 195                               HOST_WIDE_INT delta, HOST_WIDE_INT vcall_offset,
 196                               tree function_decl);
 197
 198     /* Determine whether output_mi_thunk would succeed.  */
 199     /* ??? Ideally, this hook would not exist, and success or failure
 200        would be returned from output_mi_thunk directly.  But there's
 201        too much undo-able setup involved in invoking output_mi_thunk.
 202        Could be fixed by making output_mi_thunk emit rtl instead of
 203        text to the output file.  */
 204     bool (* can_output_mi_thunk) (tree thunk_decl, HOST_WIDE_INT delta,
 205                                   HOST_WIDE_INT vcall_offset,
 206                                   tree function_decl);
 207
 208     /* Output any boilerplate text needed at the beginning of a
 209        translation unit.  */
 210     void (*file_start) (void);
 211
 212     /* Output any boilerplate text needed at the end of a
 213        translation unit.  */
 214     void (*file_end) (void);
 215
 216     /* Output an assembler pseudo-op to declare a library function name
 217        external.  */
 218     void (*external_libcall) (rtx);
 219
 220     /* Output an assembler directive to mark decl live. This instructs
 221         linker to not dead code strip this symbol.  */
 222     void (*mark_decl_preserved) (const char *);
 223
 224     /* Output a record of the command line switches that have been passed.  */
 225     print_switch_fn_type record_gcc_switches;
 226     /* The name of the section that the example ELF implementation of
 227        record_gcc_switches will use to store the information.  Target
 228        specific versions of record_gcc_switches may or may not use
 229        this information.  */
 230     const char * record_gcc_switches_section;
 231
 232     /* Output the definition of a section anchor.  */
 233     void (*output_anchor) (rtx);
 234
 235     /* Output a DTP-relative reference to a TLS symbol.  */
 236     void (*output_dwarf_dtprel) (FILE *file, int size, rtx x);
 237
 238   } asm_out;
 239
 240   /* Functions relating to instruction scheduling.  */
 241   struct sched
 242   {
 243     /* Given the current cost, COST, of an insn, INSN, calculate and
 244        return a new cost based on its relationship to DEP_INSN through
 245        the dependence LINK.  The default is to make no adjustment.  */
 246     int (* adjust_cost) (rtx insn, rtx link, rtx dep_insn, int cost);
 247
 248     /* Adjust the priority of an insn as you see fit.  Returns the new
 249        priority.  */
 250     int (* adjust_priority) (rtx, int);
 251
 252     /* Function which returns the maximum number of insns that can be
 253        scheduled in the same machine cycle.  This must be constant
 254        over an entire compilation.  The default is 1.  */
 255     int (* issue_rate) (void);
 256
 257     /* Calculate how much this insn affects how many more insns we
 258        can emit this cycle.  Default is they all cost the same.  */
 259     int (* variable_issue) (FILE *, int, rtx, int);
 260
 261     /* Initialize machine-dependent scheduling code.  */
 262     void (* md_init) (FILE *, int, int);
 263
 264     /* Finalize machine-dependent scheduling code.  */
 265     void (* md_finish) (FILE *, int);
 266
 267     /* Initialize machine-dependent function while scheduling code.  */
 268     void (* md_init_global) (FILE *, int, int);
 269
 270     /* Finalize machine-dependent function wide scheduling code.  */
 271     void (* md_finish_global) (FILE *, int);
 272
 273     /* Reorder insns in a machine-dependent fashion, in two different
 274        places.  Default does nothing.  */
 275     int (* reorder) (FILE *, int, rtx *, int *, int);
 276     int (* reorder2) (FILE *, int, rtx *, int *, int);
 277
 278     /* The following member value is a pointer to a function called
 279        after evaluation forward dependencies of insns in chain given
 280        by two parameter values (head and tail correspondingly).  */
 281     void (* dependencies_evaluation_hook) (rtx, rtx);
 282
 283     /* The values of the following four members are pointers to
 284        functions used to simplify the automaton descriptions.
 285        dfa_pre_cycle_insn and dfa_post_cycle_insn give functions
 286        returning insns which are used to change the pipeline hazard
 287        recognizer state when the new simulated processor cycle
 288        correspondingly starts and finishes.  The function defined by
 289        init_dfa_pre_cycle_insn and init_dfa_post_cycle_insn are used
 290        to initialize the corresponding insns.  The default values of
 291        the members result in not changing the automaton state when
 292        the new simulated processor cycle correspondingly starts and
 293        finishes.  */
 294     void (* init_dfa_pre_cycle_insn) (void);
 295     rtx (* dfa_pre_cycle_insn) (void);
 296     void (* init_dfa_post_cycle_insn) (void);
 297     rtx (* dfa_post_cycle_insn) (void);
 298
 299     /* The following member value is a pointer to a function returning value
 300        which defines how many insns in queue `ready' will we try for
 301        multi-pass scheduling.  If the member value is nonzero and the
 302        function returns positive value, the DFA based scheduler will make
 303        multi-pass scheduling for the first cycle.  In other words, we will
 304        try to choose ready insn which permits to start maximum number of
 305        insns on the same cycle.  */
 306     int (* first_cycle_multipass_dfa_lookahead) (void);
 307
 308     /* The following member value is pointer to a function controlling
 309        what insns from the ready insn queue will be considered for the
 310        multipass insn scheduling.  If the hook returns zero for insn
 311        passed as the parameter, the insn will be not chosen to be
 312        issued.  */
 313     int (* first_cycle_multipass_dfa_lookahead_guard) (rtx);
 314
 315     /* The following member value is pointer to a function called by
 316        the insn scheduler before issuing insn passed as the third
 317        parameter on given cycle.  If the hook returns nonzero, the
 318        insn is not issued on given processors cycle.  Instead of that,
 319        the processor cycle is advanced.  If the value passed through
 320        the last parameter is zero, the insn ready queue is not sorted
 321        on the new cycle start as usually.  The first parameter passes
 322        file for debugging output.  The second one passes the scheduler
 323        verbose level of the debugging output.  The forth and the fifth
 324        parameter values are correspondingly processor cycle on which
 325        the previous insn has been issued and the current processor
 326        cycle.  */
 327     int (* dfa_new_cycle) (FILE *, int, rtx, int, int, int *);
 328
 329     /* The following member value is a pointer to a function called by the
 330        insn scheduler.  It should return true if there exists a dependence
 331        which is considered costly by the target, between the insn
 332        DEP_PRO (&_DEP), and the insn DEP_CON (&_DEP).  The first parameter is
 333        the dep that represents the dependence between the two insns.  The
 334        second argument is the cost of the dependence as estimated by
 335        the scheduler.  The last argument is the distance in cycles
 336        between the already scheduled insn (first parameter) and the
 337        the second insn (second parameter).  */
 338     bool (* is_costly_dependence) (struct _dep *_dep, int, int);
 339
 340     /* The following member value is a pointer to a function called
 341        by the insn scheduler. This hook is called to notify the backend
 342        that new instructions were emitted.  */
 343     void (* h_i_d_extended) (void);
 344
 345     /* The following member value is a pointer to a function called
 346        by the insn scheduler.
 347        The first parameter is an instruction, the second parameter is the type
 348        of the requested speculation, and the third parameter is a pointer to the
 349        speculative pattern of the corresponding type (set if return value == 1).
 350        It should return
 351        -1, if there is no pattern, that will satisfy the requested speculation
 352        type,
 353        0, if current pattern satisfies the requested speculation type,
 354        1, if pattern of the instruction should be changed to the newly
 355        generated one.  */
 356     int (* speculate_insn) (rtx, int, rtx *);
 357
 358     /* The following member value is a pointer to a function called
 359        by the insn scheduler.  It should return true if the check instruction
 360        corresponding to the instruction passed as the parameter needs a
 361        recovery block.  */
 362     bool (* needs_block_p) (rtx);
 363
 364     /* The following member value is a pointer to a function called
 365        by the insn scheduler.  It should return a pattern for the check
 366        instruction.
 367        The first parameter is a speculative instruction, the second parameter
 368        is the label of the corresponding recovery block (or null, if it is a
 369        simple check).  If the mutation of the check is requested (e.g. from
 370        ld.c to chk.a), the third parameter is true - in this case the first
 371        parameter is the previous check.  */
 372     rtx (* gen_check) (rtx, rtx, bool);
 373
 374     /* The following member value is a pointer to a function controlling
 375        what insns from the ready insn queue will be considered for the
 376        multipass insn scheduling.  If the hook returns zero for the insn
 377        passed as the parameter, the insn will not be chosen to be
 378        issued.  This hook is used to discard speculative instructions,
 379        that stand at the first position of the ready list.  */
 380     bool (* first_cycle_multipass_dfa_lookahead_guard_spec) (rtx);
 381
 382     /* The following member value is a pointer to a function that provides
 383        information about the speculation capabilities of the target.
 384        The parameter is a pointer to spec_info variable.  */
 385     void (* set_sched_flags) (struct spec_info_def *);
 386   } sched;
 387
 388   /* Functions relating to vectorization.  */
 389   struct vectorize
 390   {
 391     /* The following member value is a pointer to a function called
 392        by the vectorizer, and return the decl of the target builtin
 393        function.  */
 394     tree (* builtin_mask_for_load) (void);
 395
 396     /* Returns a code for builtin that realizes vectorized version of
 397        function, or NULL_TREE if not available.  */
 398     tree (* builtin_vectorized_function) (unsigned, tree, tree);
 399
 400     /* Returns a code for builtin that realizes vectorized version of
 401        conversion, or NULL_TREE if not available.  */
 402     tree (* builtin_conversion) (unsigned, tree);
 403
 404     /* Target builtin that implements vector widening multiplication.
 405        builtin_mul_widen_eve computes the element-by-element products
 406        for the even elements, and builtin_mul_widen_odd computes the
 407        element-by-element products for the odd elements.  */
 408     tree (* builtin_mul_widen_even) (tree);
 409     tree (* builtin_mul_widen_odd) (tree);
 410   } vectorize;
 411
 412   /* The initial value of target_flags.  */
 413   int default_target_flags;
 414
 415   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
 416      passed to the switch; it is NULL if no argument was.  VALUE is the
 417      value of ARG if CODE specifies a UInteger option, otherwise it is
 418      1 if the positive form of the switch was used and 0 if the negative
 419      form was.  Return true if the switch was valid.  */
 420   bool (* handle_option) (size_t code, const char *arg, int value);
 421
 422   /* Return machine mode for filter value.  */
 423   enum machine_mode (* eh_return_filter_mode) (void);
 424
 425   /* Given two decls, merge their attributes and return the result.  */
 426   tree (* merge_decl_attributes) (tree, tree);
 427
 428   /* Given two types, merge their attributes and return the result.  */
 429   tree (* merge_type_attributes) (tree, tree);
 430
 431   /* Table of machine attributes and functions to handle them.
 432      Ignored if NULL.  */
 433   const struct attribute_spec *attribute_table;
 434
 435   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 436      one if they are compatible and two if they are nearly compatible
 437      (which causes a warning to be generated).  */
 438   int (* comp_type_attributes) (tree type1, tree type2);
 439
 440   /* Assign default attributes to the newly defined TYPE.  */
 441   void (* set_default_type_attributes) (tree type);
 442
 443   /* Insert attributes on the newly created DECL.  */
 444   void (* insert_attributes) (tree decl, tree *attributes);
 445
 446   /* Return true if FNDECL (which has at least one machine attribute)
 447      can be inlined despite its machine attributes, false otherwise.  */
 448   bool (* function_attribute_inlinable_p) (tree fndecl);
 449
 450   /* Return true if bitfields in RECORD_TYPE should follow the
 451      Microsoft Visual C++ bitfield layout rules.  */
 452   bool (* ms_bitfield_layout_p) (tree record_type);
 453
 454   /* True if the target supports decimal floating point.  */
 455   bool (* decimal_float_supported_p) (void);
 456
 457   /* Return true if anonymous bitfields affect structure alignment.  */
 458   bool (* align_anon_bitfield) (void);
 459
 460   /* Return true if volatile bitfields should use the narrowest type possible.
 461      Return false if they should use the container type.  */
 462   bool (* narrow_volatile_bitfield) (void);
 463
 464   /* Set up target-specific built-in functions.  */
 465   void (* init_builtins) (void);
 466
 467   /* Expand a target-specific builtin.  */
 468   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 469                           enum machine_mode mode, int ignore);
 470
 471   /* Select a replacement for a target-specific builtin.  This is done
 472      *before* regular type checking, and so allows the target to implement
 473      a crude form of function overloading.  The result is a complete
 474      expression that implements the operation.  */
 475   tree (*resolve_overloaded_builtin) (tree decl, tree params);
 476
 477   /* Fold a target-specific builtin.  */
 478   tree (* fold_builtin) (tree fndecl, tree arglist, bool ignore);
 479
 480   /* For a vendor-specific fundamental TYPE, return a pointer to
 481      a statically-allocated string containing the C++ mangling for
 482      TYPE.  In all other cases, return NULL.  */
 483   const char * (* mangle_fundamental_type) (tree type);
 484
 485   /* Make any adjustments to libfunc names needed for this target.  */
 486   void (* init_libfuncs) (void);
 487
 488   /* Given a decl, a section name, and whether the decl initializer
 489      has relocs, choose attributes for the section.  */
 490   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 491   unsigned int (* section_type_flags) (tree, const char *, int);
 492
 493   /* True if new jumps cannot be created, to replace existing ones or
 494      not, at the current point in the compilation.  */
 495   bool (* cannot_modify_jumps_p) (void);
 496
 497   /* Return a register class for which branch target register
 498      optimizations should be applied.  */
 499   int (* branch_target_register_class) (void);
 500
 501   /* Return true if branch target register optimizations should include
 502      callee-saved registers that are not already live during the current
 503      function.  AFTER_PE_GEN is true if prologues and epilogues have
 504      already been generated.  */
 505   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 506
 507   /* True if the constant X cannot be placed in the constant pool.  */
 508   bool (* cannot_force_const_mem) (rtx);
 509
 510   /* True if the insn X cannot be duplicated.  */
 511   bool (* cannot_copy_insn_p) (rtx);
 512
 513   /* True if X is considered to be commutative.  */
 514   bool (* commutative_p) (rtx, int);
 515
 516   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 517   rtx (* delegitimize_address) (rtx);
 518
 519   /* True if the given constant can be put into an object_block.  */
 520   bool (* use_blocks_for_constant_p) (enum machine_mode, rtx);
 521
 522   /* The minimum and maximum byte offsets for anchored addresses.  */
 523   HOST_WIDE_INT min_anchor_offset;
 524   HOST_WIDE_INT max_anchor_offset;
 525
 526   /* True if section anchors can be used to access the given symbol.  */
 527   bool (* use_anchors_for_symbol_p) (rtx);
 528
 529   /* True if it is OK to do sibling call optimization for the specified
 530      call expression EXP.  DECL will be the called function, or NULL if
 531      this is an indirect call.  */
 532   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 533
 534   /* True if EXP should be placed in a "small data" section.  */
 535   bool (* in_small_data_p) (tree);
 536
 537   /* True if EXP names an object for which name resolution must resolve
 538      to the current module.  */
 539   bool (* binds_local_p) (tree);
 540
 541   /* Do something target-specific to record properties of the DECL into
 542      the associated SYMBOL_REF.  */
 543   void (* encode_section_info) (tree, rtx, int);
 544
 545   /* Undo the effects of encode_section_info on the symbol string.  */
 546   const char * (* strip_name_encoding) (const char *);
 547
 548   /* If shift optabs for MODE are known to always truncate the shift count,
 549      return the mask that they apply.  Return 0 otherwise.  */
 550   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
 551
 552   /* Return the number of divisions in the given MODE that should be present,
 553      so that it is profitable to turn the division into a multiplication by
 554      the reciprocal.  */
 555   unsigned int (* min_divisions_for_recip_mul) (enum machine_mode mode);
 556
 557   /* If the representation of integral MODE is such that values are
 558      always sign-extended to a wider mode MODE_REP then return
 559      SIGN_EXTEND.  Return UNKNOWN otherwise.  */
 560   /* Note that the return type ought to be RTX_CODE, but that's not
 561      necessarily defined at this point.  */
 562   int (* mode_rep_extended) (enum machine_mode mode,
 563                              enum machine_mode mode_rep);
 564
 565   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 566   bool (* valid_pointer_mode) (enum machine_mode mode);
 567
 568   /* True if MODE is valid for the target.  By "valid", we mean able to
 569      be manipulated in non-trivial ways.  In particular, this means all
 570      the arithmetic is supported.  */
 571   bool (* scalar_mode_supported_p) (enum machine_mode mode);
 572
 573   /* Similarly for vector modes.  "Supported" here is less strict.  At
 574      least some operations are supported; need to check optabs or builtins
 575      for further details.  */
 576   bool (* vector_mode_supported_p) (enum machine_mode mode);
 577
 578   /* True if a vector is opaque.  */
 579   bool (* vector_opaque_p) (tree);
 580
 581   /* Compute a (partial) cost for rtx X.  Return true if the complete
 582      cost has been computed, and false if subexpressions should be
 583      scanned.  In either case, *TOTAL contains the cost result.  */
 584   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 585      not necessarily defined at this point.  */
 586   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 587
 588   /* Compute the cost of X, used as an address.  Never called with
 589      invalid addresses.  */
 590   int (* address_cost) (rtx x);
 591
 592   /* Return where to allocate pseudo for a given hard register initial
 593      value.  */
 594   rtx (* allocate_initial_value) (rtx x);
 595
 596   /* Given a register, this hook should return a parallel of registers
 597      to represent where to find the register pieces.  Define this hook
 598      if the register and its mode are represented in Dwarf in
 599      non-contiguous locations, or if the register should be
 600      represented in more than one register in Dwarf.  Otherwise, this
 601      hook should return NULL_RTX.  */
 602   rtx (* dwarf_register_span) (rtx);
 603
 604   /* Fetch the fixed register(s) which hold condition codes, for
 605      targets where it makes sense to look for duplicate assignments to
 606      the condition codes.  This should return true if there is such a
 607      register, false otherwise.  The arguments should be set to the
 608      fixed register numbers.  Up to two condition code registers are
 609      supported.  If there is only one for this target, the int pointed
 610      at by the second argument should be set to -1.  */
 611   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 612
 613   /* If two condition code modes are compatible, return a condition
 614      code mode which is compatible with both, such that a comparison
 615      done in the returned mode will work for both of the original
 616      modes.  If the condition code modes are not compatible, return
 617      VOIDmode.  */
 618   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 619                                              enum machine_mode);
 620
 621   /* Do machine-dependent code transformations.  Called just before
 622      delayed-branch scheduling.  */
 623   void (* machine_dependent_reorg) (void);
 624
 625   /* Create the __builtin_va_list type.  */
 626   tree (* build_builtin_va_list) (void);
 627
 628   /* Gimplifies a VA_ARG_EXPR.  */
 629   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 630                                  tree *post_p);
 631
 632   /* Validity-checking routines for PCH files, target-specific.
 633      get_pch_validity returns a pointer to the data to be stored,
 634      and stores the size in its argument.  pch_valid_p gets the same
 635      information back and returns NULL if the PCH is valid,
 636      or an error message if not.
 637   */
 638   void * (* get_pch_validity) (size_t *);
 639   const char * (* pch_valid_p) (const void *, size_t);
 640
 641   /* If nonnull, this function checks whether a PCH file with the
 642      given set of target flags can be used.  It returns NULL if so,
 643      otherwise it returns an error message.  */
 644   const char *(*check_pch_target_flags) (int);
 645
 646   /* True if the compiler should give an enum type only as many
 647      bytes as it takes to represent the range of possible values of
 648      that type.  */
 649   bool (* default_short_enums) (void);
 650
 651   /* This target hook returns an rtx that is used to store the address
 652      of the current frame into the built-in setjmp buffer.  */
 653   rtx (* builtin_setjmp_frame_value) (void);
 654
 655   /* This target hook should add STRING_CST trees for any hard regs
 656      the port wishes to automatically clobber for an asm.  */
 657   tree (* md_asm_clobbers) (tree, tree, tree);
 658
 659   /* This target hook allows the backend to specify a calling convention
 660      in the debug information.  This function actually returns an
 661      enum dwarf_calling_convention, but because of forward declarations
 662      and not wanting to include dwarf2.h everywhere target.h is included
 663      the function is being declared as an int.  */
 664   int (* dwarf_calling_convention) (tree);
 665
 666   /* This target hook allows the backend to emit frame-related insns that
 667      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
 668      engine will invoke it on insns of the form
 669        (set (reg) (unspec [...] UNSPEC_INDEX))
 670      and
 671        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
 672      to let the backend emit the call frame instructions.  */
 673   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
 674
 675   /* Perform architecture specific checking of statements gimplified
 676      from VA_ARG_EXPR.  LHS is left hand side of MODIFY_EXPR, RHS
 677      is right hand side.  Returns true if the statements doesn't need
 678      to be checked for va_list references.  */
 679   bool (* stdarg_optimize_hook) (struct stdarg_info *ai, tree lhs, tree rhs);
 680
 681   /* This target hook allows the operating system to override the DECL
 682      that represents the external variable that contains the stack
 683      protection guard variable.  The type of this DECL is ptr_type_node.  */
 684   tree (* stack_protect_guard) (void);
 685
 686   /* This target hook allows the operating system to override the CALL_EXPR
 687      that is invoked when a check vs the guard variable fails.  */
 688   tree (* stack_protect_fail) (void);
 689
 690   /* Returns NULL if target supports the insn within a doloop block,
 691      otherwise it returns an error message.  */
 692   const char * (*invalid_within_doloop) (rtx);
 693
 694   /* DECL is a variable or function with __attribute__((dllimport))
 695      specified.  Use this hook if the target needs to add extra validation
 696      checks to  handle_dll_attribute ().  */
 697   bool (* valid_dllimport_attribute_p) (tree decl);
 698
 699   /* Functions relating to calls - argument passing, returns, etc.  */
 700   struct calls {
 701     bool (*promote_function_args) (tree fntype);
 702     bool (*promote_function_return) (tree fntype);
 703     bool (*promote_prototypes) (tree fntype);
 704     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 705     bool (*return_in_memory) (tree type, tree fndecl);
 706     bool (*return_in_msb) (tree type);
 707
 708     /* Return true if a parameter must be passed by reference.  TYPE may
 709        be null if this is a libcall.  CA may be null if this query is
 710        from __builtin_va_arg.  */
 711     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 712                                tree type, bool named_arg);
 713
 714     rtx (*expand_builtin_saveregs) (void);
 715     /* Returns pretend_argument_size.  */
 716     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 717                                     tree type, int *pretend_arg_size,
 718                                     int second_time);
 719     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 720     /* Returns true if we should use
 721        targetm.calls.setup_incoming_varargs() and/or
 722        targetm.calls.strict_argument_naming().  */
 723     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 724
 725     /* Given a complex type T, return true if a parameter of type T
 726        should be passed as two scalars.  */
 727     bool (* split_complex_arg) (tree type);
 728
 729     /* Return true if type T, mode MODE, may not be passed in registers,
 730        but must be passed on the stack.  */
 731     /* ??? This predicate should be applied strictly after pass-by-reference.
 732        Need audit to verify that this is the case.  */
 733     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 734
 735     /* Return true if type TYPE, mode MODE, which is passed by reference,
 736        should have the object copy generated by the callee rather than
 737        the caller.  It is never called for TYPE requiring constructors.  */
 738     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 739                             tree type, bool named);
 740
 741     /* Return zero for arguments passed entirely on the stack or entirely
 742        in registers.  If passed in both, return the number of bytes passed
 743        in registers; the balance is therefore passed on the stack.  */
 744     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 745                                tree type, bool named);
 746
 747     /* Return the diagnostic message string if function without a prototype
 748        is not allowed for this 'val' argument; NULL otherwise. */
 749     const char *(*invalid_arg_for_unprototyped_fn) (tree typelist,
 750                                                     tree funcdecl, tree val);
 751
 752     /* Return an rtx for the return value location of the function
 753        specified by FN_DECL_OR_TYPE with a return type of RET_TYPE.  */
 754     rtx (*function_value) (tree ret_type, tree fn_decl_or_type,
 755                            bool outgoing);
 756
 757     /* Return an rtx for the argument pointer incoming to the
 758        current function.  */
 759     rtx (*internal_arg_pointer) (void);
 760   } calls;
 761
 762   /* Return the diagnostic message string if conversion from FROMTYPE
 763      to TOTYPE is not allowed, NULL otherwise.  */
 764   const char *(*invalid_conversion) (tree fromtype, tree totype);
 765
 766   /* Return the diagnostic message string if the unary operation OP is
 767      not permitted on TYPE, NULL otherwise.  */
 768   const char *(*invalid_unary_op) (int op, tree type);
 769
 770   /* Return the diagnostic message string if the binary operation OP
 771      is not permitted on TYPE1 and TYPE2, NULL otherwise.  */
 772   const char *(*invalid_binary_op) (int op, tree type1, tree type2);
 773
 774   /* Return the class for a secondary reload, and fill in extra information.  */
 775   enum reg_class (*secondary_reload) (bool, rtx, enum reg_class,
 776                                       enum machine_mode,
 777                                       struct secondary_reload_info *);
 778
 779   /* Functions specific to the C++ frontend.  */
 780   struct cxx {
 781     /* Return the integer type used for guard variables.  */
 782     tree (*guard_type) (void);
 783     /* Return true if only the low bit of the guard should be tested.  */
 784     bool (*guard_mask_bit) (void);
 785     /* Returns the size of the array cookie for an array of type.  */
 786     tree (*get_cookie_size) (tree);
 787     /* Returns true if the element size should be stored in the
 788        array cookie.  */
 789     bool (*cookie_has_size) (void);
 790     /* Allows backends to perform additional processing when
 791        deciding if a class should be exported or imported.  */
 792     int (*import_export_class) (tree, int);
 793     /* Returns true if constructors and destructors return "this".  */
 794     bool (*cdtor_returns_this) (void);
 795     /* Returns true if the key method for a class can be an inline
 796        function, so long as it is not declared inline in the class
 797        itself.  Returning true is the behavior required by the Itanium
 798        C++ ABI.  */
 799     bool (*key_method_may_be_inline) (void);
 800     /* DECL is a virtual table, virtual table table, typeinfo object,
 801        or other similar implicit class data object that will be
 802        emitted with external linkage in this translation unit.  No ELF
 803        visibility has been explicitly specified.  If the target needs
 804        to specify a visibility other than that of the containing class,
 805        use this hook to set DECL_VISIBILITY and
 806        DECL_VISIBILITY_SPECIFIED.  */
 807     void (*determine_class_data_visibility) (tree decl);
 808     /* Returns true (the default) if virtual tables and other
 809        similar implicit class data objects are always COMDAT if they
 810        have external linkage.  If this hook returns false, then
 811        class data for classes whose virtual table will be emitted in
 812        only one translation unit will not be COMDAT.  */
 813     bool (*class_data_always_comdat) (void);
 814     /* Returns true (the default) if the RTTI for the basic types,
 815        which is always defined in the C++ runtime, should be COMDAT;
 816        false if it should not be COMDAT.  */
 817     bool (*library_rtti_comdat) (void);
 818     /* Returns true if __aeabi_atexit should be used to register static
 819        destructors.  */
 820     bool (*use_aeabi_atexit) (void);
 821     /* Returns true if target may use atexit in the same manner as
 822     __cxa_atexit  to register static destructors.  */
 823     bool (*use_atexit_for_cxa_atexit) (void);
 824     /* TYPE is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that
 825        has just been defined.  Use this hook to make adjustments to the
 826        class  (eg, tweak visibility or perform any other required
 827        target modifications).  */
 828     void (*adjust_class_at_definition) (tree type);
 829   } cxx;
 830
 831   /* For targets that need to mark extra registers as live on entry to
 832      the function, they should define this target hook and set their
 833      bits in the bitmap passed in. */
 834   void (*live_on_entry) (bitmap);
 835
 836   /* True if unwinding tables should be generated by default.  */
 837   bool unwind_tables_default;
 838
 839   /* Leave the boolean fields at the end.  */
 840
 841   /* True if arbitrary sections are supported.  */
 842   bool have_named_sections;
 843
 844   /* True if we can create zeroed data by switching to a BSS section
 845      and then using ASM_OUTPUT_SKIP to allocate the space.  */
 846   bool have_switchable_bss_sections;
 847
 848   /* True if "native" constructors and destructors are supported,
 849      false if we're using collect2 for the job.  */
 850   bool have_ctors_dtors;
 851
 852   /* True if thread-local storage is supported.  */
 853   bool have_tls;
 854
 855   /* True if a small readonly data section is supported.  */
 856   bool have_srodata_section;
 857
 858   /* True if EH frame info sections should be zero-terminated.  */
 859   bool terminate_dw2_eh_frame_info;
 860
 861   /* True if #NO_APP should be emitted at the beginning of
 862      assembly output.  */
 863   bool file_start_app_off;
 864
 865   /* True if output_file_directive should be called for main_input_filename
 866      at the beginning of assembly output.  */
 867   bool file_start_file_directive;
 868
 869   /* True if #pragma redefine_extname is to be supported.  */
 870   bool handle_pragma_redefine_extname;
 871
 872   /* True if #pragma extern_prefix is to be supported.  */
 873   bool handle_pragma_extern_prefix;
 874
 875   /* True if the target is allowed to reorder memory accesses unless
 876      synchronization is explicitly requested.  */
 877   bool relaxed_ordering;
 878
 879   /* Returns true if we should generate exception tables for use with the
 880      ARM EABI.  The effects the encoding of function exception specifications.
 881    */
 882   bool arm_eabi_unwinder;
 883
 884   /* Leave the boolean fields at the end.  */
 885 };
 886
 887 extern struct gcc_target targetm;
 888
 889 #endif /* GCC_TARGET_H */