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 globalise 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     /* Target builtin that implements vector widening multiplication.
 401        builtin_mul_widen_eve computes the element-by-element products
 402        for the even elements, and builtin_mul_widen_odd computes the
 403        element-by-element products for the odd elements.  */
 404     tree (* builtin_mul_widen_even) (tree);
 405     tree (* builtin_mul_widen_odd) (tree);
 406   } vectorize;
 407
 408   /* The initial value of target_flags.  */
 409   int default_target_flags;
 410
 411   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
 412      passed to the switch; it is NULL if no argument was.  VALUE is the
 413      value of ARG if CODE specifies a UInteger option, otherwise it is
 414      1 if the positive form of the switch was used and 0 if the negative
 415      form was.  Return true if the switch was valid.  */
 416   bool (* handle_option) (size_t code, const char *arg, int value);
 417
 418   /* Return machine mode for filter value.  */
 419   enum machine_mode (* eh_return_filter_mode) (void);
 420
 421   /* Given two decls, merge their attributes and return the result.  */
 422   tree (* merge_decl_attributes) (tree, tree);
 423
 424   /* Given two types, merge their attributes and return the result.  */
 425   tree (* merge_type_attributes) (tree, tree);
 426
 427   /* Table of machine attributes and functions to handle them.
 428      Ignored if NULL.  */
 429   const struct attribute_spec *attribute_table;
 430
 431   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 432      one if they are compatible and two if they are nearly compatible
 433      (which causes a warning to be generated).  */
 434   int (* comp_type_attributes) (tree type1, tree type2);
 435
 436   /* Assign default attributes to the newly defined TYPE.  */
 437   void (* set_default_type_attributes) (tree type);
 438
 439   /* Insert attributes on the newly created DECL.  */
 440   void (* insert_attributes) (tree decl, tree *attributes);
 441
 442   /* Return true if FNDECL (which has at least one machine attribute)
 443      can be inlined despite its machine attributes, false otherwise.  */
 444   bool (* function_attribute_inlinable_p) (tree fndecl);
 445
 446   /* Return true if bitfields in RECORD_TYPE should follow the
 447      Microsoft Visual C++ bitfield layout rules.  */
 448   bool (* ms_bitfield_layout_p) (tree record_type);
 449
 450   /* True if the target supports decimal floating point.  */
 451   bool (* decimal_float_supported_p) (void);
 452
 453   /* Return true if anonymous bitfields affect structure alignment.  */
 454   bool (* align_anon_bitfield) (void);
 455
 456   /* Return true if volatile bitfields should use the narrowest type possible.
 457      Return false if they should use the container type.  */
 458   bool (* narrow_volatile_bitfield) (void);
 459
 460   /* Set up target-specific built-in functions.  */
 461   void (* init_builtins) (void);
 462
 463   /* Expand a target-specific builtin.  */
 464   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 465                           enum machine_mode mode, int ignore);
 466
 467   /* Select a replacement for a target-specific builtin.  This is done
 468      *before* regular type checking, and so allows the target to implement
 469      a crude form of function overloading.  The result is a complete
 470      expression that implements the operation.  */
 471   tree (*resolve_overloaded_builtin) (tree decl, tree params);
 472
 473   /* Fold a target-specific builtin.  */
 474   tree (* fold_builtin) (tree fndecl, tree arglist, bool ignore);
 475
 476   /* For a vendor-specific fundamental TYPE, return a pointer to
 477      a statically-allocated string containing the C++ mangling for
 478      TYPE.  In all other cases, return NULL.  */
 479   const char * (* mangle_fundamental_type) (tree type);
 480
 481   /* Make any adjustments to libfunc names needed for this target.  */
 482   void (* init_libfuncs) (void);
 483
 484   /* Given a decl, a section name, and whether the decl initializer
 485      has relocs, choose attributes for the section.  */
 486   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 487   unsigned int (* section_type_flags) (tree, const char *, int);
 488
 489   /* True if new jumps cannot be created, to replace existing ones or
 490      not, at the current point in the compilation.  */
 491   bool (* cannot_modify_jumps_p) (void);
 492
 493   /* Return a register class for which branch target register
 494      optimizations should be applied.  */
 495   int (* branch_target_register_class) (void);
 496
 497   /* Return true if branch target register optimizations should include
 498      callee-saved registers that are not already live during the current
 499      function.  AFTER_PE_GEN is true if prologues and epilogues have
 500      already been generated.  */
 501   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 502
 503   /* True if the constant X cannot be placed in the constant pool.  */
 504   bool (* cannot_force_const_mem) (rtx);
 505
 506   /* True if the insn X cannot be duplicated.  */
 507   bool (* cannot_copy_insn_p) (rtx);
 508
 509   /* True if X is considered to be commutative.  */
 510   bool (* commutative_p) (rtx, int);
 511
 512   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 513   rtx (* delegitimize_address) (rtx);
 514
 515   /* True if the given constant can be put into an object_block.  */
 516   bool (* use_blocks_for_constant_p) (enum machine_mode, rtx);
 517
 518   /* The minimum and maximum byte offsets for anchored addresses.  */
 519   HOST_WIDE_INT min_anchor_offset;
 520   HOST_WIDE_INT max_anchor_offset;
 521
 522   /* True if section anchors can be used to access the given symbol.  */
 523   bool (* use_anchors_for_symbol_p) (rtx);
 524
 525   /* True if it is OK to do sibling call optimization for the specified
 526      call expression EXP.  DECL will be the called function, or NULL if
 527      this is an indirect call.  */
 528   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 529
 530   /* True if EXP should be placed in a "small data" section.  */
 531   bool (* in_small_data_p) (tree);
 532
 533   /* True if EXP names an object for which name resolution must resolve
 534      to the current module.  */
 535   bool (* binds_local_p) (tree);
 536
 537   /* Do something target-specific to record properties of the DECL into
 538      the associated SYMBOL_REF.  */
 539   void (* encode_section_info) (tree, rtx, int);
 540
 541   /* Undo the effects of encode_section_info on the symbol string.  */
 542   const char * (* strip_name_encoding) (const char *);
 543
 544   /* If shift optabs for MODE are known to always truncate the shift count,
 545      return the mask that they apply.  Return 0 otherwise.  */
 546   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
 547
 548   /* Return the number of divisions in the given MODE that should be present,
 549      so that it is profitable to turn the division into a multiplication by
 550      the reciprocal.  */
 551   unsigned int (* min_divisions_for_recip_mul) (enum machine_mode mode);
 552
 553   /* If the representation of integral MODE is such that values are
 554      always sign-extended to a wider mode MODE_REP then return
 555      SIGN_EXTEND.  Return UNKNOWN otherwise.  */
 556   /* Note that the return type ought to be RTX_CODE, but that's not
 557      necessarily defined at this point.  */
 558   int (* mode_rep_extended) (enum machine_mode mode,
 559                              enum machine_mode mode_rep);
 560
 561   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 562   bool (* valid_pointer_mode) (enum machine_mode mode);
 563
 564   /* True if MODE is valid for the target.  By "valid", we mean able to
 565      be manipulated in non-trivial ways.  In particular, this means all
 566      the arithmetic is supported.  */
 567   bool (* scalar_mode_supported_p) (enum machine_mode mode);
 568
 569   /* Similarly for vector modes.  "Supported" here is less strict.  At
 570      least some operations are supported; need to check optabs or builtins
 571      for further details.  */
 572   bool (* vector_mode_supported_p) (enum machine_mode mode);
 573
 574   /* True if a vector is opaque.  */
 575   bool (* vector_opaque_p) (tree);
 576
 577   /* Compute a (partial) cost for rtx X.  Return true if the complete
 578      cost has been computed, and false if subexpressions should be
 579      scanned.  In either case, *TOTAL contains the cost result.  */
 580   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 581      not necessarily defined at this point.  */
 582   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 583
 584   /* Compute the cost of X, used as an address.  Never called with
 585      invalid addresses.  */
 586   int (* address_cost) (rtx x);
 587
 588   /* Return where to allocate pseudo for a given hard register initial
 589      value.  */
 590   rtx (* allocate_initial_value) (rtx x);
 591
 592   /* Given a register, this hook should return a parallel of registers
 593      to represent where to find the register pieces.  Define this hook
 594      if the register and its mode are represented in Dwarf in
 595      non-contiguous locations, or if the register should be
 596      represented in more than one register in Dwarf.  Otherwise, this
 597      hook should return NULL_RTX.  */
 598   rtx (* dwarf_register_span) (rtx);
 599
 600   /* Fetch the fixed register(s) which hold condition codes, for
 601      targets where it makes sense to look for duplicate assignments to
 602      the condition codes.  This should return true if there is such a
 603      register, false otherwise.  The arguments should be set to the
 604      fixed register numbers.  Up to two condition code registers are
 605      supported.  If there is only one for this target, the int pointed
 606      at by the second argument should be set to -1.  */
 607   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 608
 609   /* If two condition code modes are compatible, return a condition
 610      code mode which is compatible with both, such that a comparison
 611      done in the returned mode will work for both of the original
 612      modes.  If the condition code modes are not compatible, return
 613      VOIDmode.  */
 614   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 615                                              enum machine_mode);
 616
 617   /* Do machine-dependent code transformations.  Called just before
 618      delayed-branch scheduling.  */
 619   void (* machine_dependent_reorg) (void);
 620
 621   /* Create the __builtin_va_list type.  */
 622   tree (* build_builtin_va_list) (void);
 623
 624   /* Gimplifies a VA_ARG_EXPR.  */
 625   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 626                                  tree *post_p);
 627
 628   /* Validity-checking routines for PCH files, target-specific.
 629      get_pch_validity returns a pointer to the data to be stored,
 630      and stores the size in its argument.  pch_valid_p gets the same
 631      information back and returns NULL if the PCH is valid,
 632      or an error message if not.
 633   */
 634   void * (* get_pch_validity) (size_t *);
 635   const char * (* pch_valid_p) (const void *, size_t);
 636
 637   /* If nonnull, this function checks whether a PCH file with the
 638      given set of target flags can be used.  It returns NULL if so,
 639      otherwise it returns an error message.  */
 640   const char *(*check_pch_target_flags) (int);
 641
 642   /* True if the compiler should give an enum type only as many
 643      bytes as it takes to represent the range of possible values of
 644      that type.  */
 645   bool (* default_short_enums) (void);
 646
 647   /* This target hook returns an rtx that is used to store the address
 648      of the current frame into the built-in setjmp buffer.  */
 649   rtx (* builtin_setjmp_frame_value) (void);
 650
 651   /* This target hook should add STRING_CST trees for any hard regs
 652      the port wishes to automatically clobber for an asm.  */
 653   tree (* md_asm_clobbers) (tree, tree, tree);
 654
 655   /* This target hook allows the backend to specify a calling convention
 656      in the debug information.  This function actually returns an
 657      enum dwarf_calling_convention, but because of forward declarations
 658      and not wanting to include dwarf2.h everywhere target.h is included
 659      the function is being declared as an int.  */
 660   int (* dwarf_calling_convention) (tree);
 661
 662   /* This target hook allows the backend to emit frame-related insns that
 663      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
 664      engine will invoke it on insns of the form
 665        (set (reg) (unspec [...] UNSPEC_INDEX))
 666      and
 667        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
 668      to let the backend emit the call frame instructions.  */
 669   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
 670
 671   /* Perform architecture specific checking of statements gimplified
 672      from VA_ARG_EXPR.  LHS is left hand side of MODIFY_EXPR, RHS
 673      is right hand side.  Returns true if the statements doesn't need
 674      to be checked for va_list references.  */
 675   bool (* stdarg_optimize_hook) (struct stdarg_info *ai, tree lhs, tree rhs);
 676
 677   /* This target hook allows the operating system to override the DECL
 678      that represents the external variable that contains the stack
 679      protection guard variable.  The type of this DECL is ptr_type_node.  */
 680   tree (* stack_protect_guard) (void);
 681
 682   /* This target hook allows the operating system to override the CALL_EXPR
 683      that is invoked when a check vs the guard variable fails.  */
 684   tree (* stack_protect_fail) (void);
 685
 686   /* Returns NULL if target supports the insn within a doloop block,
 687      otherwise it returns an error message.  */
 688   const char * (*invalid_within_doloop) (rtx);
 689
 690   /* DECL is a variable or function with __attribute__((dllimport))
 691      specified.  Use this hook if the target needs to add extra validation
 692      checks to  handle_dll_attribute ().  */
 693   bool (* valid_dllimport_attribute_p) (tree decl);
 694
 695   /* Functions relating to calls - argument passing, returns, etc.  */
 696   struct calls {
 697     bool (*promote_function_args) (tree fntype);
 698     bool (*promote_function_return) (tree fntype);
 699     bool (*promote_prototypes) (tree fntype);
 700     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 701     bool (*return_in_memory) (tree type, tree fndecl);
 702     bool (*return_in_msb) (tree type);
 703
 704     /* Return true if a parameter must be passed by reference.  TYPE may
 705        be null if this is a libcall.  CA may be null if this query is
 706        from __builtin_va_arg.  */
 707     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 708                                tree type, bool named_arg);
 709
 710     rtx (*expand_builtin_saveregs) (void);
 711     /* Returns pretend_argument_size.  */
 712     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 713                                     tree type, int *pretend_arg_size,
 714                                     int second_time);
 715     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 716     /* Returns true if we should use
 717        targetm.calls.setup_incoming_varargs() and/or
 718        targetm.calls.strict_argument_naming().  */
 719     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 720
 721     /* Given a complex type T, return true if a parameter of type T
 722        should be passed as two scalars.  */
 723     bool (* split_complex_arg) (tree type);
 724
 725     /* Return true if type T, mode MODE, may not be passed in registers,
 726        but must be passed on the stack.  */
 727     /* ??? This predicate should be applied strictly after pass-by-reference.
 728        Need audit to verify that this is the case.  */
 729     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 730
 731     /* Return true if type TYPE, mode MODE, which is passed by reference,
 732        should have the object copy generated by the callee rather than
 733        the caller.  It is never called for TYPE requiring constructors.  */
 734     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 735                             tree type, bool named);
 736
 737     /* Return zero for arguments passed entirely on the stack or entirely
 738        in registers.  If passed in both, return the number of bytes passed
 739        in registers; the balance is therefore passed on the stack.  */
 740     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 741                                tree type, bool named);
 742
 743     /* Return the diagnostic message string if function without a prototype
 744        is not allowed for this 'val' argument; NULL otherwise. */
 745     const char *(*invalid_arg_for_unprototyped_fn) (tree typelist,
 746                                                     tree funcdecl, tree val);
 747
 748     /* Return an rtx for the return value location of the function
 749        specified by FN_DECL_OR_TYPE with a return type of RET_TYPE.  */
 750     rtx (*function_value) (tree ret_type, tree fn_decl_or_type,
 751                            bool outgoing);
 752
 753     /* Return an rtx for the argument pointer incoming to the
 754        current function.  */
 755     rtx (*internal_arg_pointer) (void);
 756   } calls;
 757
 758   /* Return the diagnostic message string if conversion from FROMTYPE
 759      to TOTYPE is not allowed, NULL otherwise.  */
 760   const char *(*invalid_conversion) (tree fromtype, tree totype);
 761
 762   /* Return the diagnostic message string if the unary operation OP is
 763      not permitted on TYPE, NULL otherwise.  */
 764   const char *(*invalid_unary_op) (int op, tree type);
 765
 766   /* Return the diagnostic message string if the binary operation OP
 767      is not permitted on TYPE1 and TYPE2, NULL otherwise.  */
 768   const char *(*invalid_binary_op) (int op, tree type1, tree type2);
 769
 770   /* Return the class for a secondary reload, and fill in extra information.  */
 771   enum reg_class (*secondary_reload) (bool, rtx, enum reg_class,
 772                                       enum machine_mode,
 773                                       struct secondary_reload_info *);
 774
 775   /* Functions specific to the C++ frontend.  */
 776   struct cxx {
 777     /* Return the integer type used for guard variables.  */
 778     tree (*guard_type) (void);
 779     /* Return true if only the low bit of the guard should be tested.  */
 780     bool (*guard_mask_bit) (void);
 781     /* Returns the size of the array cookie for an array of type.  */
 782     tree (*get_cookie_size) (tree);
 783     /* Returns true if the element size should be stored in the
 784        array cookie.  */
 785     bool (*cookie_has_size) (void);
 786     /* Allows backends to perform additional processing when
 787        deciding if a class should be exported or imported.  */
 788     int (*import_export_class) (tree, int);
 789     /* Returns true if constructors and destructors return "this".  */
 790     bool (*cdtor_returns_this) (void);
 791     /* Returns true if the key method for a class can be an inline
 792        function, so long as it is not declared inline in the class
 793        itself.  Returning true is the behavior required by the Itanium
 794        C++ ABI.  */
 795     bool (*key_method_may_be_inline) (void);
 796     /* DECL is a virtual table, virtual table table, typeinfo object,
 797        or other similar implicit class data object that will be
 798        emitted with external linkage in this translation unit.  No ELF
 799        visibility has been explicitly specified.  If the target needs
 800        to specify a visibility other than that of the containing class,
 801        use this hook to set DECL_VISIBILITY and
 802        DECL_VISIBILITY_SPECIFIED.  */
 803     void (*determine_class_data_visibility) (tree decl);
 804     /* Returns true (the default) if virtual tables and other
 805        similar implicit class data objects are always COMDAT if they
 806        have external linkage.  If this hook returns false, then
 807        class data for classes whose virtual table will be emitted in
 808        only one translation unit will not be COMDAT.  */
 809     bool (*class_data_always_comdat) (void);
 810     /* Returns true (the default) if the RTTI for the basic types,
 811        which is always defined in the C++ runtime, should be COMDAT;
 812        false if it should not be COMDAT.  */
 813     bool (*library_rtti_comdat) (void);
 814     /* Returns true if __aeabi_atexit should be used to register static
 815        destructors.  */
 816     bool (*use_aeabi_atexit) (void);
 817     /* Returns true if target may use atexit in the same manner as
 818     __cxa_atexit  to register static destructors.  */
 819     bool (*use_atexit_for_cxa_atexit) (void);
 820     /* TYPE is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that
 821        has just been defined.  Use this hook to make adjustments to the
 822        class  (eg, tweak visibility or perform any other required
 823        target modifications).  */
 824     void (*adjust_class_at_definition) (tree type);
 825   } cxx;
 826
 827   /* For targets that need to mark extra registers as live on entry to
 828      the function, they should define this target hook and set their
 829      bits in the bitmap passed in. */
 830   void (*live_on_entry) (bitmap);
 831
 832   /* True if unwinding tables should be generated by default.  */
 833   bool unwind_tables_default;
 834
 835   /* Leave the boolean fields at the end.  */
 836
 837   /* True if arbitrary sections are supported.  */
 838   bool have_named_sections;
 839
 840   /* True if we can create zeroed data by switching to a BSS section
 841      and then using ASM_OUTPUT_SKIP to allocate the space.  */
 842   bool have_switchable_bss_sections;
 843
 844   /* True if "native" constructors and destructors are supported,
 845      false if we're using collect2 for the job.  */
 846   bool have_ctors_dtors;
 847
 848   /* True if thread-local storage is supported.  */
 849   bool have_tls;
 850
 851   /* True if a small readonly data section is supported.  */
 852   bool have_srodata_section;
 853
 854   /* True if EH frame info sections should be zero-terminated.  */
 855   bool terminate_dw2_eh_frame_info;
 856
 857   /* True if #NO_APP should be emitted at the beginning of
 858      assembly output.  */
 859   bool file_start_app_off;
 860
 861   /* True if output_file_directive should be called for main_input_filename
 862      at the beginning of assembly output.  */
 863   bool file_start_file_directive;
 864
 865   /* True if #pragma redefine_extname is to be supported.  */
 866   bool handle_pragma_redefine_extname;
 867
 868   /* True if #pragma extern_prefix is to be supported.  */
 869   bool handle_pragma_extern_prefix;
 870
 871   /* True if the target is allowed to reorder memory accesses unless
 872      synchronization is explicitly requested.  */
 873   bool relaxed_ordering;
 874
 875   /* Returns true if we should generate exception tables for use with the
 876      ARM EABI.  The effects the encoding of function exception specifications.
 877    */
 878   bool arm_eabi_unwinder;
 879
 880   /* Leave the boolean fields at the end.  */
 881 };
 882
 883 extern struct gcc_target targetm;
 884
 885 #endif /* GCC_TARGET_H */