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
  88 struct gcc_target
  89 {
  90   /* Functions that output assembler for the target.  */
  91   struct asm_out
  92   {
  93     /* Opening and closing parentheses for asm expression grouping.  */
  94     const char *open_paren, *close_paren;
  95
  96     /* Assembler instructions for creating various kinds of integer object.  */
  97     const char *byte_op;
  98     struct asm_int_op
  99     {
 100       const char *hi;
 101       const char *si;
 102       const char *di;
 103       const char *ti;
 104     } aligned_op, unaligned_op;
 105
 106     /* Try to output the assembler code for an integer object whose
 107        value is given by X.  SIZE is the size of the object in bytes and
 108        ALIGNED_P indicates whether it is aligned.  Return true if
 109        successful.  Only handles cases for which BYTE_OP, ALIGNED_OP
 110        and UNALIGNED_OP are NULL.  */
 111     bool (* integer) (rtx x, unsigned int size, int aligned_p);
 112
 113     /* Output code that will globalize a label.  */
 114     void (* globalize_label) (FILE *, const char *);
 115
 116     /* Output code that will emit a label for unwind info, if this
 117        target requires such labels.  Second argument is the decl the
 118        unwind info is associated with, third is a boolean: true if
 119        this is for exception handling, fourth is a boolean: true if
 120        this is only a placeholder for an omitted FDE.  */
 121     void (* unwind_label) (FILE *, tree, int, int);
 122
 123     /* Output code that will emit a label to divide up the exception
 124        table.  */
 125     void (* except_table_label) (FILE *);
 126
 127     /* Emit any directives required to unwind this instruction.  */
 128     void (* unwind_emit) (FILE *, rtx);
 129
 130     /* Output an internal label.  */
 131     void (* internal_label) (FILE *, const char *, unsigned long);
 132
 133     /* Emit a ttype table reference to a typeinfo object.  */
 134     bool (* ttype) (rtx);
 135
 136     /* Emit an assembler directive to set visibility for the symbol
 137        associated with the tree decl.  */
 138     void (* visibility) (tree, int);
 139
 140     /* Output the assembler code for entry to a function.  */
 141     void (* function_prologue) (FILE *, HOST_WIDE_INT);
 142
 143     /* Output the assembler code for end of prologue.  */
 144     void (* function_end_prologue) (FILE *);
 145
 146     /* Output the assembler code for start of epilogue.  */
 147     void (* function_begin_epilogue) (FILE *);
 148
 149     /* Output the assembler code for function exit.  */
 150     void (* function_epilogue) (FILE *, HOST_WIDE_INT);
 151
 152     /* Initialize target-specific sections.  */
 153     void (* init_sections) (void);
 154
 155     /* Tell assembler to change to section NAME with attributes FLAGS.
 156        If DECL is non-NULL, it is the VAR_DECL or FUNCTION_DECL with
 157        which this section is associated.  */
 158     void (* named_section) (const char *name, unsigned int flags, tree decl);
 159
 160     /* Return a section for EXP.  It may be a DECL or a constant.  RELOC
 161        is nonzero if runtime relocations must be applied; bit 1 will be
 162        set if the runtime relocations require non-local name resolution.
 163        ALIGN is the required alignment of the data.  */
 164     section *(* select_section) (tree, int, unsigned HOST_WIDE_INT);
 165
 166     /* Return a section for X.  MODE is X's mode and ALIGN is its
 167        alignment in bits.  */
 168     section *(* select_rtx_section) (enum machine_mode, rtx,
 169                                      unsigned HOST_WIDE_INT);
 170
 171     /* Select a unique section name for DECL.  RELOC is the same as
 172        for SELECT_SECTION.  */
 173     void (* unique_section) (tree, int);
 174
 175     /* Return the readonly data section associated with function DECL.  */
 176     section *(* function_rodata_section) (tree);
 177
 178     /* Output a constructor for a symbol with a given priority.  */
 179     void (* constructor) (rtx, int);
 180
 181     /* Output a destructor for a symbol with a given priority.  */
 182     void (* destructor) (rtx, int);
 183
 184     /* Output the assembler code for a thunk function.  THUNK_DECL is the
 185        declaration for the thunk function itself, FUNCTION is the decl for
 186        the target function.  DELTA is an immediate constant offset to be
 187        added to THIS.  If VCALL_OFFSET is nonzero, the word at
 188        *(*this + vcall_offset) should be added to THIS.  */
 189     void (* output_mi_thunk) (FILE *file, tree thunk_decl,
 190                               HOST_WIDE_INT delta, HOST_WIDE_INT vcall_offset,
 191                               tree function_decl);
 192
 193     /* Determine whether output_mi_thunk would succeed.  */
 194     /* ??? Ideally, this hook would not exist, and success or failure
 195        would be returned from output_mi_thunk directly.  But there's
 196        too much undo-able setup involved in invoking output_mi_thunk.
 197        Could be fixed by making output_mi_thunk emit rtl instead of
 198        text to the output file.  */
 199     bool (* can_output_mi_thunk) (tree thunk_decl, HOST_WIDE_INT delta,
 200                                   HOST_WIDE_INT vcall_offset,
 201                                   tree function_decl);
 202
 203     /* Output any boilerplate text needed at the beginning of a
 204        translation unit.  */
 205     void (*file_start) (void);
 206
 207     /* Output any boilerplate text needed at the end of a
 208        translation unit.  */
 209     void (*file_end) (void);
 210
 211     /* Output an assembler pseudo-op to declare a library function name
 212        external.  */
 213     void (*external_libcall) (rtx);
 214
 215     /* Output an assembler directive to mark decl live. This instructs
 216         linker to not dead code strip this symbol.  */
 217     void (*mark_decl_preserved) (const char *);
 218
 219     /* Output a record of the command line switches that have been passed.  */
 220     print_switch_fn_type record_gcc_switches;
 221     /* The name of the section that the example ELF implementation of
 222        record_gcc_switches will use to store the information.  Target
 223        specific versions of record_gcc_switches may or may not use
 224        this information.  */
 225     const char * record_gcc_switches_section;
 226
 227     /* Output the definition of a section anchor.  */
 228     void (*output_anchor) (rtx);
 229
 230     /* Output a DTP-relative reference to a TLS symbol.  */
 231     void (*output_dwarf_dtprel) (FILE *file, int size, rtx x);
 232
 233   } asm_out;
 234
 235   /* Functions relating to instruction scheduling.  */
 236   struct sched
 237   {
 238     /* Given the current cost, COST, of an insn, INSN, calculate and
 239        return a new cost based on its relationship to DEP_INSN through
 240        the dependence LINK.  The default is to make no adjustment.  */
 241     int (* adjust_cost) (rtx insn, rtx link, rtx def_insn, int cost);
 242
 243     /* Adjust the priority of an insn as you see fit.  Returns the new
 244        priority.  */
 245     int (* adjust_priority) (rtx, int);
 246
 247     /* Function which returns the maximum number of insns that can be
 248        scheduled in the same machine cycle.  This must be constant
 249        over an entire compilation.  The default is 1.  */
 250     int (* issue_rate) (void);
 251
 252     /* Calculate how much this insn affects how many more insns we
 253        can emit this cycle.  Default is they all cost the same.  */
 254     int (* variable_issue) (FILE *, int, rtx, int);
 255
 256     /* Initialize machine-dependent scheduling code.  */
 257     void (* md_init) (FILE *, int, int);
 258
 259     /* Finalize machine-dependent scheduling code.  */
 260     void (* md_finish) (FILE *, int);
 261
 262     /* Initialize machine-dependent function while scheduling code.  */
 263     void (* md_init_global) (FILE *, int, int);
 264
 265     /* Finalize machine-dependent function wide scheduling code.  */
 266     void (* md_finish_global) (FILE *, int);
 267
 268     /* Reorder insns in a machine-dependent fashion, in two different
 269        places.  Default does nothing.  */
 270     int (* reorder) (FILE *, int, rtx *, int *, int);
 271     int (* reorder2) (FILE *, int, rtx *, int *, int);
 272
 273     /* The following member value is a pointer to a function called
 274        after evaluation forward dependencies of insns in chain given
 275        by two parameter values (head and tail correspondingly).  */
 276     void (* dependencies_evaluation_hook) (rtx, rtx);
 277
 278     /* The values of the following four members are pointers to
 279        functions used to simplify the automaton descriptions.
 280        dfa_pre_cycle_insn and dfa_post_cycle_insn give functions
 281        returning insns which are used to change the pipeline hazard
 282        recognizer state when the new simulated processor cycle
 283        correspondingly starts and finishes.  The function defined by
 284        init_dfa_pre_cycle_insn and init_dfa_post_cycle_insn are used
 285        to initialize the corresponding insns.  The default values of
 286        the members result in not changing the automaton state when
 287        the new simulated processor cycle correspondingly starts and
 288        finishes.  */
 289     void (* init_dfa_pre_cycle_insn) (void);
 290     rtx (* dfa_pre_cycle_insn) (void);
 291     void (* init_dfa_post_cycle_insn) (void);
 292     rtx (* dfa_post_cycle_insn) (void);
 293
 294     /* The following member value is a pointer to a function returning value
 295        which defines how many insns in queue `ready' will we try for
 296        multi-pass scheduling.  If the member value is nonzero and the
 297        function returns positive value, the DFA based scheduler will make
 298        multi-pass scheduling for the first cycle.  In other words, we will
 299        try to choose ready insn which permits to start maximum number of
 300        insns on the same cycle.  */
 301     int (* first_cycle_multipass_dfa_lookahead) (void);
 302
 303     /* The following member value is pointer to a function controlling
 304        what insns from the ready insn queue will be considered for the
 305        multipass insn scheduling.  If the hook returns zero for insn
 306        passed as the parameter, the insn will be not chosen to be
 307        issued.  */
 308     int (* first_cycle_multipass_dfa_lookahead_guard) (rtx);
 309
 310     /* The following member value is pointer to a function called by
 311        the insn scheduler before issuing insn passed as the third
 312        parameter on given cycle.  If the hook returns nonzero, the
 313        insn is not issued on given processors cycle.  Instead of that,
 314        the processor cycle is advanced.  If the value passed through
 315        the last parameter is zero, the insn ready queue is not sorted
 316        on the new cycle start as usually.  The first parameter passes
 317        file for debugging output.  The second one passes the scheduler
 318        verbose level of the debugging output.  The forth and the fifth
 319        parameter values are correspondingly processor cycle on which
 320        the previous insn has been issued and the current processor
 321        cycle.  */
 322     int (* dfa_new_cycle) (FILE *, int, rtx, int, int, int *);
 323
 324     /* The following member value is a pointer to a function called
 325        by the insn scheduler.  It should return true if there exists a
 326        dependence which is considered costly by the target, between
 327        the insn passed as the first parameter, and the insn passed as
 328        the second parameter.  The third parameter is the INSN_DEPEND
 329        link that represents the dependence between the two insns.  The
 330        fourth argument is the cost of the dependence as estimated by
 331        the scheduler.  The last argument is the distance in cycles
 332        between the already scheduled insn (first parameter) and the
 333        the second insn (second parameter).  */
 334     bool (* is_costly_dependence) (rtx, rtx, rtx, int, int);
 335
 336     /* Given the current cost, COST, of an insn, INSN, calculate and
 337        return a new cost based on its relationship to DEP_INSN through the
 338        dependence of type DEP_TYPE.  The default is to make no adjustment.  */
 339     int (* adjust_cost_2) (rtx insn, int, rtx def_insn, int cost);
 340
 341     /* The following member value is a pointer to a function called
 342        by the insn scheduler. This hook is called to notify the backend
 343        that new instructions were emitted.  */
 344     void (* h_i_d_extended) (void);
 345
 346     /* The following member value is a pointer to a function called
 347        by the insn scheduler.
 348        The first parameter is an instruction, the second parameter is the type
 349        of the requested speculation, and the third parameter is a pointer to the
 350        speculative pattern of the corresponding type (set if return value == 1).
 351        It should return
 352        -1, if there is no pattern, that will satisfy the requested speculation
 353        type,
 354        0, if current pattern satisfies the requested speculation type,
 355        1, if pattern of the instruction should be changed to the newly
 356        generated one.  */
 357     int (* speculate_insn) (rtx, int, rtx *);
 358
 359     /* The following member value is a pointer to a function called
 360        by the insn scheduler.  It should return true if the check instruction
 361        corresponding to the instruction passed as the parameter needs a
 362        recovery block.  */
 363     bool (* needs_block_p) (rtx);
 364
 365     /* The following member value is a pointer to a function called
 366        by the insn scheduler.  It should return a pattern for the check
 367        instruction.
 368        The first parameter is a speculative instruction, the second parameter
 369        is the label of the corresponding recovery block (or null, if it is a
 370        simple check).  If the mutation of the check is requested (e.g. from
 371        ld.c to chk.a), the third parameter is true - in this case the first
 372        parameter is the previous check.  */
 373     rtx (* gen_check) (rtx, rtx, bool);
 374
 375     /* The following member value is a pointer to a function controlling
 376        what insns from the ready insn queue will be considered for the
 377        multipass insn scheduling.  If the hook returns zero for the insn
 378        passed as the parameter, the insn will not be chosen to be
 379        issued.  This hook is used to discard speculative instructions,
 380        that stand at the first position of the ready list.  */
 381     bool (* first_cycle_multipass_dfa_lookahead_guard_spec) (rtx);
 382
 383     /* The following member value is a pointer to a function that provides
 384        information about the speculation capabilities of the target.
 385        The parameter is a pointer to spec_info variable.  */
 386     void (* set_sched_flags) (struct spec_info_def *);
 387   } sched;
 388
 389   /* Functions relating to vectorization.  */
 390   struct vectorize
 391   {
 392     /* The following member value is a pointer to a function called
 393        by the vectorizer, and return the decl of the target builtin
 394        function.  */
 395     tree (* builtin_mask_for_load) (void);
 396
 397     /* Returns a code for builtin that realizes vectorized version of
 398        function, or NULL_TREE if not available.  */
 399     tree (* builtin_vectorized_function) (unsigned, tree);
 400
 401     /* Target builtin that implements vector widening multiplication.
 402        builtin_mul_widen_eve computes the element-by-element products
 403        for the even elements, and builtin_mul_widen_odd computes the
 404        element-by-element products for the odd elements.  */
 405     tree (* builtin_mul_widen_even) (tree);
 406     tree (* builtin_mul_widen_odd) (tree);
 407   } vectorize;
 408
 409   /* The initial value of target_flags.  */
 410   int default_target_flags;
 411
 412   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
 413      passed to the switch; it is NULL if no argument was.  VALUE is the
 414      value of ARG if CODE specifies a UInteger option, otherwise it is
 415      1 if the positive form of the switch was used and 0 if the negative
 416      form was.  Return true if the switch was valid.  */
 417   bool (* handle_option) (size_t code, const char *arg, int value);
 418
 419   /* Return machine mode for filter value.  */
 420   enum machine_mode (* eh_return_filter_mode) (void);
 421
 422   /* Given two decls, merge their attributes and return the result.  */
 423   tree (* merge_decl_attributes) (tree, tree);
 424
 425   /* Given two types, merge their attributes and return the result.  */
 426   tree (* merge_type_attributes) (tree, tree);
 427
 428   /* Table of machine attributes and functions to handle them.
 429      Ignored if NULL.  */
 430   const struct attribute_spec *attribute_table;
 431
 432   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 433      one if they are compatible and two if they are nearly compatible
 434      (which causes a warning to be generated).  */
 435   int (* comp_type_attributes) (tree type1, tree type2);
 436
 437   /* Assign default attributes to the newly defined TYPE.  */
 438   void (* set_default_type_attributes) (tree type);
 439
 440   /* Insert attributes on the newly created DECL.  */
 441   void (* insert_attributes) (tree decl, tree *attributes);
 442
 443   /* Return true if FNDECL (which has at least one machine attribute)
 444      can be inlined despite its machine attributes, false otherwise.  */
 445   bool (* function_attribute_inlinable_p) (tree fndecl);
 446
 447   /* Return true if bitfields in RECORD_TYPE should follow the
 448      Microsoft Visual C++ bitfield layout rules.  */
 449   bool (* ms_bitfield_layout_p) (tree record_type);
 450
 451   /* True if the target supports decimal floating point.  */
 452   bool (* decimal_float_supported_p) (void);
 453
 454   /* Return true if anonymous bitfields affect structure alignment.  */
 455   bool (* align_anon_bitfield) (void);
 456
 457   /* Return true if volatile bitfields should use the narrowest type possible.
 458      Return false if they should use the container type.  */
 459   bool (* narrow_volatile_bitfield) (void);
 460
 461   /* Set up target-specific built-in functions.  */
 462   void (* init_builtins) (void);
 463
 464   /* Expand a target-specific builtin.  */
 465   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 466                           enum machine_mode mode, int ignore);
 467
 468   /* Select a replacement for a target-specific builtin.  This is done
 469      *before* regular type checking, and so allows the target to implement
 470      a crude form of function overloading.  The result is a complete
 471      expression that implements the operation.  */
 472   tree (*resolve_overloaded_builtin) (tree decl, tree params);
 473
 474   /* Fold a target-specific builtin.  */
 475   tree (* fold_builtin) (tree fndecl, tree arglist, bool ignore);
 476
 477   /* For a vendor-specific fundamental TYPE, return a pointer to
 478      a statically-allocated string containing the C++ mangling for
 479      TYPE.  In all other cases, return NULL.  */
 480   const char * (* mangle_fundamental_type) (tree type);
 481
 482   /* Make any adjustments to libfunc names needed for this target.  */
 483   void (* init_libfuncs) (void);
 484
 485   /* Given a decl, a section name, and whether the decl initializer
 486      has relocs, choose attributes for the section.  */
 487   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 488   unsigned int (* section_type_flags) (tree, const char *, int);
 489
 490   /* True if new jumps cannot be created, to replace existing ones or
 491      not, at the current point in the compilation.  */
 492   bool (* cannot_modify_jumps_p) (void);
 493
 494   /* Return a register class for which branch target register
 495      optimizations should be applied.  */
 496   int (* branch_target_register_class) (void);
 497
 498   /* Return true if branch target register optimizations should include
 499      callee-saved registers that are not already live during the current
 500      function.  AFTER_PE_GEN is true if prologues and epilogues have
 501      already been generated.  */
 502   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 503
 504   /* True if the constant X cannot be placed in the constant pool.  */
 505   bool (* cannot_force_const_mem) (rtx);
 506
 507   /* True if the insn X cannot be duplicated.  */
 508   bool (* cannot_copy_insn_p) (rtx);
 509
 510   /* True if X is considered to be commutative.  */
 511   bool (* commutative_p) (rtx, int);
 512
 513   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 514   rtx (* delegitimize_address) (rtx);
 515
 516   /* True if the given constant can be put into an object_block.  */
 517   bool (* use_blocks_for_constant_p) (enum machine_mode, rtx);
 518
 519   /* The minimum and maximum byte offsets for anchored addresses.  */
 520   HOST_WIDE_INT min_anchor_offset;
 521   HOST_WIDE_INT max_anchor_offset;
 522
 523   /* True if section anchors can be used to access the given symbol.  */
 524   bool (* use_anchors_for_symbol_p) (rtx);
 525
 526   /* True if it is OK to do sibling call optimization for the specified
 527      call expression EXP.  DECL will be the called function, or NULL if
 528      this is an indirect call.  */
 529   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 530
 531   /* True if EXP should be placed in a "small data" section.  */
 532   bool (* in_small_data_p) (tree);
 533
 534   /* True if EXP names an object for which name resolution must resolve
 535      to the current module.  */
 536   bool (* binds_local_p) (tree);
 537
 538   /* Do something target-specific to record properties of the DECL into
 539      the associated SYMBOL_REF.  */
 540   void (* encode_section_info) (tree, rtx, int);
 541
 542   /* Undo the effects of encode_section_info on the symbol string.  */
 543   const char * (* strip_name_encoding) (const char *);
 544
 545   /* If shift optabs for MODE are known to always truncate the shift count,
 546      return the mask that they apply.  Return 0 otherwise.  */
 547   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
 548
 549   /* Return the number of divisions in the given MODE that should be present,
 550      so that it is profitable to turn the division into a multiplication by
 551      the reciprocal.  */
 552   unsigned int (* min_divisions_for_recip_mul) (enum machine_mode mode);
 553
 554   /* If the representation of integral MODE is such that values are
 555      always sign-extended to a wider mode MODE_REP then return
 556      SIGN_EXTEND.  Return UNKNOWN otherwise.  */
 557   /* Note that the return type ought to be RTX_CODE, but that's not
 558      necessarily defined at this point.  */
 559   int (* mode_rep_extended) (enum machine_mode mode,
 560                              enum machine_mode mode_rep);
 561
 562   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 563   bool (* valid_pointer_mode) (enum machine_mode mode);
 564
 565   /* True if MODE is valid for the target.  By "valid", we mean able to
 566      be manipulated in non-trivial ways.  In particular, this means all
 567      the arithmetic is supported.  */
 568   bool (* scalar_mode_supported_p) (enum machine_mode mode);
 569
 570   /* Similarly for vector modes.  "Supported" here is less strict.  At
 571      least some operations are supported; need to check optabs or builtins
 572      for further details.  */
 573   bool (* vector_mode_supported_p) (enum machine_mode mode);
 574
 575   /* True if a vector is opaque.  */
 576   bool (* vector_opaque_p) (tree);
 577
 578   /* Compute a (partial) cost for rtx X.  Return true if the complete
 579      cost has been computed, and false if subexpressions should be
 580      scanned.  In either case, *TOTAL contains the cost result.  */
 581   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 582      not necessarily defined at this point.  */
 583   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 584
 585   /* Compute the cost of X, used as an address.  Never called with
 586      invalid addresses.  */
 587   int (* address_cost) (rtx x);
 588
 589   /* Return where to allocate pseudo for a given hard register initial
 590      value.  */
 591   rtx (* allocate_initial_value) (rtx x);
 592
 593   /* Given a register, this hook should return a parallel of registers
 594      to represent where to find the register pieces.  Define this hook
 595      if the register and its mode are represented in Dwarf in
 596      non-contiguous locations, or if the register should be
 597      represented in more than one register in Dwarf.  Otherwise, this
 598      hook should return NULL_RTX.  */
 599   rtx (* dwarf_register_span) (rtx);
 600
 601   /* Fetch the fixed register(s) which hold condition codes, for
 602      targets where it makes sense to look for duplicate assignments to
 603      the condition codes.  This should return true if there is such a
 604      register, false otherwise.  The arguments should be set to the
 605      fixed register numbers.  Up to two condition code registers are
 606      supported.  If there is only one for this target, the int pointed
 607      at by the second argument should be set to -1.  */
 608   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 609
 610   /* If two condition code modes are compatible, return a condition
 611      code mode which is compatible with both, such that a comparison
 612      done in the returned mode will work for both of the original
 613      modes.  If the condition code modes are not compatible, return
 614      VOIDmode.  */
 615   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 616                                              enum machine_mode);
 617
 618   /* Do machine-dependent code transformations.  Called just before
 619      delayed-branch scheduling.  */
 620   void (* machine_dependent_reorg) (void);
 621
 622   /* Create the __builtin_va_list type.  */
 623   tree (* build_builtin_va_list) (void);
 624
 625   /* Gimplifies a VA_ARG_EXPR.  */
 626   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 627                                  tree *post_p);
 628
 629   /* Validity-checking routines for PCH files, target-specific.
 630      get_pch_validity returns a pointer to the data to be stored,
 631      and stores the size in its argument.  pch_valid_p gets the same
 632      information back and returns NULL if the PCH is valid,
 633      or an error message if not.
 634   */
 635   void * (* get_pch_validity) (size_t *);
 636   const char * (* pch_valid_p) (const void *, size_t);
 637
 638   /* If nonnull, this function checks whether a PCH file with the
 639      given set of target flags can be used.  It returns NULL if so,
 640      otherwise it returns an error message.  */
 641   const char *(*check_pch_target_flags) (int);
 642
 643   /* True if the compiler should give an enum type only as many
 644      bytes as it takes to represent the range of possible values of
 645      that type.  */
 646   bool (* default_short_enums) (void);
 647
 648   /* This target hook returns an rtx that is used to store the address
 649      of the current frame into the built-in setjmp buffer.  */
 650   rtx (* builtin_setjmp_frame_value) (void);
 651
 652   /* This target hook should add STRING_CST trees for any hard regs
 653      the port wishes to automatically clobber for an asm.  */
 654   tree (* md_asm_clobbers) (tree, tree, tree);
 655
 656   /* This target hook allows the backend to specify a calling convention
 657      in the debug information.  This function actually returns an
 658      enum dwarf_calling_convention, but because of forward declarations
 659      and not wanting to include dwarf2.h everywhere target.h is included
 660      the function is being declared as an int.  */
 661   int (* dwarf_calling_convention) (tree);
 662
 663   /* This target hook allows the backend to emit frame-related insns that
 664      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
 665      engine will invoke it on insns of the form
 666        (set (reg) (unspec [...] UNSPEC_INDEX))
 667      and
 668        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
 669      to let the backend emit the call frame instructions.  */
 670   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
 671
 672   /* Perform architecture specific checking of statements gimplified
 673      from VA_ARG_EXPR.  LHS is left hand side of MODIFY_EXPR, RHS
 674      is right hand side.  Returns true if the statements doesn't need
 675      to be checked for va_list references.  */
 676   bool (* stdarg_optimize_hook) (struct stdarg_info *ai, tree lhs, tree rhs);
 677
 678   /* This target hook allows the operating system to override the DECL
 679      that represents the external variable that contains the stack
 680      protection guard variable.  The type of this DECL is ptr_type_node.  */
 681   tree (* stack_protect_guard) (void);
 682
 683   /* This target hook allows the operating system to override the CALL_EXPR
 684      that is invoked when a check vs the guard variable fails.  */
 685   tree (* stack_protect_fail) (void);
 686
 687   /* Returns NULL if target supports the insn within a doloop block,
 688      otherwise it returns an error message.  */
 689   const char * (*invalid_within_doloop) (rtx);
 690
 691   /* DECL is a variable or function with __attribute__((dllimport))
 692      specified.  Use this hook if the target needs to add extra validation
 693      checks to  handle_dll_attribute ().  */
 694   bool (* valid_dllimport_attribute_p) (tree decl);
 695
 696   /* Functions relating to calls - argument passing, returns, etc.  */
 697   struct calls {
 698     bool (*promote_function_args) (tree fntype);
 699     bool (*promote_function_return) (tree fntype);
 700     bool (*promote_prototypes) (tree fntype);
 701     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 702     bool (*return_in_memory) (tree type, tree fndecl);
 703     bool (*return_in_msb) (tree type);
 704
 705     /* Return true if a parameter must be passed by reference.  TYPE may
 706        be null if this is a libcall.  CA may be null if this query is
 707        from __builtin_va_arg.  */
 708     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 709                                tree type, bool named_arg);
 710
 711     rtx (*expand_builtin_saveregs) (void);
 712     /* Returns pretend_argument_size.  */
 713     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 714                                     tree type, int *pretend_arg_size,
 715                                     int second_time);
 716     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 717     /* Returns true if we should use
 718        targetm.calls.setup_incoming_varargs() and/or
 719        targetm.calls.strict_argument_naming().  */
 720     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 721
 722     /* Given a complex type T, return true if a parameter of type T
 723        should be passed as two scalars.  */
 724     bool (* split_complex_arg) (tree type);
 725
 726     /* Return true if type T, mode MODE, may not be passed in registers,
 727        but must be passed on the stack.  */
 728     /* ??? This predicate should be applied strictly after pass-by-reference.
 729        Need audit to verify that this is the case.  */
 730     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 731
 732     /* Return true if type TYPE, mode MODE, which is passed by reference,
 733        should have the object copy generated by the callee rather than
 734        the caller.  It is never called for TYPE requiring constructors.  */
 735     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 736                             tree type, bool named);
 737
 738     /* Return zero for arguments passed entirely on the stack or entirely
 739        in registers.  If passed in both, return the number of bytes passed
 740        in registers; the balance is therefore passed on the stack.  */
 741     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 742                                tree type, bool named);
 743
 744     /* Return the diagnostic message string if function without a prototype
 745        is not allowed for this 'val' argument; NULL otherwise. */
 746     const char *(*invalid_arg_for_unprototyped_fn) (tree typelist,
 747                                                     tree funcdecl, tree val);
 748
 749     /* Return an rtx for the return value location of the function
 750        specified by FN_DECL_OR_TYPE with a return type of RET_TYPE.  */
 751     rtx (*function_value) (tree ret_type, tree fn_decl_or_type,
 752                            bool outgoing);
 753
 754     /* Return an rtx for the argument pointer incoming to the
 755        current function.  */
 756     rtx (*internal_arg_pointer) (void);
 757   } calls;
 758
 759   /* Return the diagnostic message string if conversion from FROMTYPE
 760      to TOTYPE is not allowed, NULL otherwise.  */
 761   const char *(*invalid_conversion) (tree fromtype, tree totype);
 762
 763   /* Return the diagnostic message string if the unary operation OP is
 764      not permitted on TYPE, NULL otherwise.  */
 765   const char *(*invalid_unary_op) (int op, tree type);
 766
 767   /* Return the diagnostic message string if the binary operation OP
 768      is not permitted on TYPE1 and TYPE2, NULL otherwise.  */
 769   const char *(*invalid_binary_op) (int op, tree type1, tree type2);
 770
 771   /* Return the class for a secondary reload, and fill in extra information.  */
 772   enum reg_class (*secondary_reload) (bool, rtx, enum reg_class,
 773                                       enum machine_mode,
 774                                       struct secondary_reload_info *);
 775
 776   /* Functions specific to the C++ frontend.  */
 777   struct cxx {
 778     /* Return the integer type used for guard variables.  */
 779     tree (*guard_type) (void);
 780     /* Return true if only the low bit of the guard should be tested.  */
 781     bool (*guard_mask_bit) (void);
 782     /* Returns the size of the array cookie for an array of type.  */
 783     tree (*get_cookie_size) (tree);
 784     /* Returns true if the element size should be stored in the
 785        array cookie.  */
 786     bool (*cookie_has_size) (void);
 787     /* Allows backends to perform additional processing when
 788        deciding if a class should be exported or imported.  */
 789     int (*import_export_class) (tree, int);
 790     /* Returns true if constructors and destructors return "this".  */
 791     bool (*cdtor_returns_this) (void);
 792     /* Returns true if the key method for a class can be an inline
 793        function, so long as it is not declared inline in the class
 794        itself.  Returning true is the behavior required by the Itanium
 795        C++ ABI.  */
 796     bool (*key_method_may_be_inline) (void);
 797     /* DECL is a virtual table, virtual table table, typeinfo object,
 798        or other similar implicit class data object that will be
 799        emitted with external linkage in this translation unit.  No ELF
 800        visibility has been explicitly specified.  If the target needs
 801        to specify a visibility other than that of the containing class,
 802        use this hook to set DECL_VISIBILITY and
 803        DECL_VISIBILITY_SPECIFIED.  */
 804     void (*determine_class_data_visibility) (tree decl);
 805     /* Returns true (the default) if virtual tables and other
 806        similar implicit class data objects are always COMDAT if they
 807        have external linkage.  If this hook returns false, then
 808        class data for classes whose virtual table will be emitted in
 809        only one translation unit will not be COMDAT.  */
 810     bool (*class_data_always_comdat) (void);
 811     /* Returns true (the default) if the RTTI for the basic types,
 812        which is always defined in the C++ runtime, should be COMDAT;
 813        false if it should not be COMDAT.  */
 814     bool (*library_rtti_comdat) (void);
 815     /* Returns true if __aeabi_atexit should be used to register static
 816        destructors.  */
 817     bool (*use_aeabi_atexit) (void);
 818     /* Returns true if target may use atexit in the same manner as
 819     __cxa_atexit  to register static destructors.  */
 820     bool (*use_atexit_for_cxa_atexit) (void);
 821     /* TYPE is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that
 822        has just been defined.  Use this hook to make adjustments to the
 823        class  (eg, tweak visibility or perform any other required
 824        target modifications).  */
 825     void (*adjust_class_at_definition) (tree type);
 826   } cxx;
 827
 828   /* For targets that need to mark extra registers as live on entry to
 829      the function, they should define this target hook and set their
 830      bits in the bitmap passed in. */
 831   void (*live_on_entry) (bitmap);
 832
 833   /* True if unwinding tables should be generated by default.  */
 834   bool unwind_tables_default;
 835
 836   /* Leave the boolean fields at the end.  */
 837
 838   /* True if arbitrary sections are supported.  */
 839   bool have_named_sections;
 840
 841   /* True if we can create zeroed data by switching to a BSS section
 842      and then using ASM_OUTPUT_SKIP to allocate the space.  */
 843   bool have_switchable_bss_sections;
 844
 845   /* True if "native" constructors and destructors are supported,
 846      false if we're using collect2 for the job.  */
 847   bool have_ctors_dtors;
 848
 849   /* True if thread-local storage is supported.  */
 850   bool have_tls;
 851
 852   /* True if a small readonly data section is supported.  */
 853   bool have_srodata_section;
 854
 855   /* True if EH frame info sections should be zero-terminated.  */
 856   bool terminate_dw2_eh_frame_info;
 857
 858   /* True if #NO_APP should be emitted at the beginning of
 859      assembly output.  */
 860   bool file_start_app_off;
 861
 862   /* True if output_file_directive should be called for main_input_filename
 863      at the beginning of assembly output.  */
 864   bool file_start_file_directive;
 865
 866   /* True if #pragma redefine_extname is to be supported.  */
 867   bool handle_pragma_redefine_extname;
 868
 869   /* True if #pragma extern_prefix is to be supported.  */
 870   bool handle_pragma_extern_prefix;
 871
 872   /* True if the target is allowed to reorder memory accesses unless
 873      synchronization is explicitly requested.  */
 874   bool relaxed_ordering;
 875
 876   /* Returns true if we should generate exception tables for use with the
 877      ARM EABI.  The effects the encoding of function exception specifications.
 878    */
 879   bool arm_eabi_unwinder;
 880
 881   /* Leave the boolean fields at the end.  */
 882 };
 883
 884 extern struct gcc_target targetm;
 885
 886 #endif /* GCC_TARGET_H */