gcc/target.h

   1 /* Data structure definitions for a generic GCC target.
   2    Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007
   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 mask describing how relocations should be treated when
 166        selecting sections.  Bit 1 should be set if global relocations
 167        should be placed in a read-write section; bit 0 should be set if
 168        local relocations should be placed in a read-write section.  */
 169     int (*reloc_rw_mask) (void);
 170
 171     /* Return a section for EXP.  It may be a DECL or a constant.  RELOC
 172        is nonzero if runtime relocations must be applied; bit 1 will be
 173        set if the runtime relocations require non-local name resolution.
 174        ALIGN is the required alignment of the data.  */
 175     section *(* select_section) (tree, int, unsigned HOST_WIDE_INT);
 176
 177     /* Return a section for X.  MODE is X's mode and ALIGN is its
 178        alignment in bits.  */
 179     section *(* select_rtx_section) (enum machine_mode, rtx,
 180                                      unsigned HOST_WIDE_INT);
 181
 182     /* Select a unique section name for DECL.  RELOC is the same as
 183        for SELECT_SECTION.  */
 184     void (* unique_section) (tree, int);
 185
 186     /* Return the readonly data section associated with function DECL.  */
 187     section *(* function_rodata_section) (tree);
 188
 189     /* Output a constructor for a symbol with a given priority.  */
 190     void (* constructor) (rtx, int);
 191
 192     /* Output a destructor for a symbol with a given priority.  */
 193     void (* destructor) (rtx, int);
 194
 195     /* Output the assembler code for a thunk function.  THUNK_DECL is the
 196        declaration for the thunk function itself, FUNCTION is the decl for
 197        the target function.  DELTA is an immediate constant offset to be
 198        added to THIS.  If VCALL_OFFSET is nonzero, the word at
 199        *(*this + vcall_offset) should be added to THIS.  */
 200     void (* output_mi_thunk) (FILE *file, tree thunk_decl,
 201                               HOST_WIDE_INT delta, HOST_WIDE_INT vcall_offset,
 202                               tree function_decl);
 203
 204     /* Determine whether output_mi_thunk would succeed.  */
 205     /* ??? Ideally, this hook would not exist, and success or failure
 206        would be returned from output_mi_thunk directly.  But there's
 207        too much undo-able setup involved in invoking output_mi_thunk.
 208        Could be fixed by making output_mi_thunk emit rtl instead of
 209        text to the output file.  */
 210     bool (* can_output_mi_thunk) (tree thunk_decl, HOST_WIDE_INT delta,
 211                                   HOST_WIDE_INT vcall_offset,
 212                                   tree function_decl);
 213
 214     /* Output any boilerplate text needed at the beginning of a
 215        translation unit.  */
 216     void (*file_start) (void);
 217
 218     /* Output any boilerplate text needed at the end of a
 219        translation unit.  */
 220     void (*file_end) (void);
 221
 222     /* Output an assembler pseudo-op to declare a library function name
 223        external.  */
 224     void (*external_libcall) (rtx);
 225
 226     /* Output an assembler directive to mark decl live. This instructs
 227         linker to not dead code strip this symbol.  */
 228     void (*mark_decl_preserved) (const char *);
 229
 230     /* Output a record of the command line switches that have been passed.  */
 231     print_switch_fn_type record_gcc_switches;
 232     /* The name of the section that the example ELF implementation of
 233        record_gcc_switches will use to store the information.  Target
 234        specific versions of record_gcc_switches may or may not use
 235        this information.  */
 236     const char * record_gcc_switches_section;
 237
 238     /* Output the definition of a section anchor.  */
 239     void (*output_anchor) (rtx);
 240
 241     /* Output a DTP-relative reference to a TLS symbol.  */
 242     void (*output_dwarf_dtprel) (FILE *file, int size, rtx x);
 243
 244   } asm_out;
 245
 246   /* Functions relating to instruction scheduling.  */
 247   struct sched
 248   {
 249     /* Given the current cost, COST, of an insn, INSN, calculate and
 250        return a new cost based on its relationship to DEP_INSN through
 251        the dependence LINK.  The default is to make no adjustment.  */
 252     int (* adjust_cost) (rtx insn, rtx link, rtx dep_insn, int cost);
 253
 254     /* Adjust the priority of an insn as you see fit.  Returns the new
 255        priority.  */
 256     int (* adjust_priority) (rtx, int);
 257
 258     /* Function which returns the maximum number of insns that can be
 259        scheduled in the same machine cycle.  This must be constant
 260        over an entire compilation.  The default is 1.  */
 261     int (* issue_rate) (void);
 262
 263     /* Calculate how much this insn affects how many more insns we
 264        can emit this cycle.  Default is they all cost the same.  */
 265     int (* variable_issue) (FILE *, int, rtx, int);
 266
 267     /* Initialize machine-dependent scheduling code.  */
 268     void (* md_init) (FILE *, int, int);
 269
 270     /* Finalize machine-dependent scheduling code.  */
 271     void (* md_finish) (FILE *, int);
 272
 273     /* Initialize machine-dependent function while scheduling code.  */
 274     void (* md_init_global) (FILE *, int, int);
 275
 276     /* Finalize machine-dependent function wide scheduling code.  */
 277     void (* md_finish_global) (FILE *, int);
 278
 279     /* Reorder insns in a machine-dependent fashion, in two different
 280        places.  Default does nothing.  */
 281     int (* reorder) (FILE *, int, rtx *, int *, int);
 282     int (* reorder2) (FILE *, int, rtx *, int *, int);
 283
 284     /* The following member value is a pointer to a function called
 285        after evaluation forward dependencies of insns in chain given
 286        by two parameter values (head and tail correspondingly).  */
 287     void (* dependencies_evaluation_hook) (rtx, rtx);
 288
 289     /* The values of the following four members are pointers to
 290        functions used to simplify the automaton descriptions.
 291        dfa_pre_cycle_insn and dfa_post_cycle_insn give functions
 292        returning insns which are used to change the pipeline hazard
 293        recognizer state when the new simulated processor cycle
 294        correspondingly starts and finishes.  The function defined by
 295        init_dfa_pre_cycle_insn and init_dfa_post_cycle_insn are used
 296        to initialize the corresponding insns.  The default values of
 297        the members result in not changing the automaton state when
 298        the new simulated processor cycle correspondingly starts and
 299        finishes.  */
 300     void (* init_dfa_pre_cycle_insn) (void);
 301     rtx (* dfa_pre_cycle_insn) (void);
 302     void (* init_dfa_post_cycle_insn) (void);
 303     rtx (* dfa_post_cycle_insn) (void);
 304
 305     /* The following member value is a pointer to a function returning value
 306        which defines how many insns in queue `ready' will we try for
 307        multi-pass scheduling.  If the member value is nonzero and the
 308        function returns positive value, the DFA based scheduler will make
 309        multi-pass scheduling for the first cycle.  In other words, we will
 310        try to choose ready insn which permits to start maximum number of
 311        insns on the same cycle.  */
 312     int (* first_cycle_multipass_dfa_lookahead) (void);
 313
 314     /* The following member value is pointer to a function controlling
 315        what insns from the ready insn queue will be considered for the
 316        multipass insn scheduling.  If the hook returns zero for insn
 317        passed as the parameter, the insn will be not chosen to be
 318        issued.  */
 319     int (* first_cycle_multipass_dfa_lookahead_guard) (rtx);
 320
 321     /* The following member value is pointer to a function called by
 322        the insn scheduler before issuing insn passed as the third
 323        parameter on given cycle.  If the hook returns nonzero, the
 324        insn is not issued on given processors cycle.  Instead of that,
 325        the processor cycle is advanced.  If the value passed through
 326        the last parameter is zero, the insn ready queue is not sorted
 327        on the new cycle start as usually.  The first parameter passes
 328        file for debugging output.  The second one passes the scheduler
 329        verbose level of the debugging output.  The forth and the fifth
 330        parameter values are correspondingly processor cycle on which
 331        the previous insn has been issued and the current processor
 332        cycle.  */
 333     int (* dfa_new_cycle) (FILE *, int, rtx, int, int, int *);
 334
 335     /* The following member value is a pointer to a function called by the
 336        insn scheduler.  It should return true if there exists a dependence
 337        which is considered costly by the target, between the insn
 338        DEP_PRO (&_DEP), and the insn DEP_CON (&_DEP).  The first parameter is
 339        the dep that represents the dependence between the two insns.  The
 340        second argument is the cost of the dependence as estimated by
 341        the scheduler.  The last argument is the distance in cycles
 342        between the already scheduled insn (first parameter) and the
 343        the second insn (second parameter).  */
 344     bool (* is_costly_dependence) (struct _dep *_dep, int, int);
 345
 346     /* The following member value is a pointer to a function called
 347        by the insn scheduler. This hook is called to notify the backend
 348        that new instructions were emitted.  */
 349     void (* h_i_d_extended) (void);
 350
 351     /* The following member value is a pointer to a function called
 352        by the insn scheduler.
 353        The first parameter is an instruction, the second parameter is the type
 354        of the requested speculation, and the third parameter is a pointer to the
 355        speculative pattern of the corresponding type (set if return value == 1).
 356        It should return
 357        -1, if there is no pattern, that will satisfy the requested speculation
 358        type,
 359        0, if current pattern satisfies the requested speculation type,
 360        1, if pattern of the instruction should be changed to the newly
 361        generated one.  */
 362     int (* speculate_insn) (rtx, int, rtx *);
 363
 364     /* The following member value is a pointer to a function called
 365        by the insn scheduler.  It should return true if the check instruction
 366        corresponding to the instruction passed as the parameter needs a
 367        recovery block.  */
 368     bool (* needs_block_p) (rtx);
 369
 370     /* The following member value is a pointer to a function called
 371        by the insn scheduler.  It should return a pattern for the check
 372        instruction.
 373        The first parameter is a speculative instruction, the second parameter
 374        is the label of the corresponding recovery block (or null, if it is a
 375        simple check).  If the mutation of the check is requested (e.g. from
 376        ld.c to chk.a), the third parameter is true - in this case the first
 377        parameter is the previous check.  */
 378     rtx (* gen_check) (rtx, rtx, bool);
 379
 380     /* The following member value is a pointer to a function controlling
 381        what insns from the ready insn queue will be considered for the
 382        multipass insn scheduling.  If the hook returns zero for the insn
 383        passed as the parameter, the insn will not be chosen to be
 384        issued.  This hook is used to discard speculative instructions,
 385        that stand at the first position of the ready list.  */
 386     bool (* first_cycle_multipass_dfa_lookahead_guard_spec) (rtx);
 387
 388     /* The following member value is a pointer to a function that provides
 389        information about the speculation capabilities of the target.
 390        The parameter is a pointer to spec_info variable.  */
 391     void (* set_sched_flags) (struct spec_info_def *);
 392   } sched;
 393
 394   /* Functions relating to vectorization.  */
 395   struct vectorize
 396   {
 397     /* The following member value is a pointer to a function called
 398        by the vectorizer, and return the decl of the target builtin
 399        function.  */
 400     tree (* builtin_mask_for_load) (void);
 401
 402     /* Returns a code for builtin that realizes vectorized version of
 403        function, or NULL_TREE if not available.  */
 404     tree (* builtin_vectorized_function) (unsigned, tree, tree);
 405
 406     /* Returns a code for builtin that realizes vectorized version of
 407        conversion, or NULL_TREE if not available.  */
 408     tree (* builtin_conversion) (unsigned, tree);
 409
 410     /* Target builtin that implements vector widening multiplication.
 411        builtin_mul_widen_eve computes the element-by-element products
 412        for the even elements, and builtin_mul_widen_odd computes the
 413        element-by-element products for the odd elements.  */
 414     tree (* builtin_mul_widen_even) (tree);
 415     tree (* builtin_mul_widen_odd) (tree);
 416   } vectorize;
 417
 418   /* The initial value of target_flags.  */
 419   int default_target_flags;
 420
 421   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
 422      passed to the switch; it is NULL if no argument was.  VALUE is the
 423      value of ARG if CODE specifies a UInteger option, otherwise it is
 424      1 if the positive form of the switch was used and 0 if the negative
 425      form was.  Return true if the switch was valid.  */
 426   bool (* handle_option) (size_t code, const char *arg, int value);
 427
 428   /* Return machine mode for filter value.  */
 429   enum machine_mode (* eh_return_filter_mode) (void);
 430
 431   /* Given two decls, merge their attributes and return the result.  */
 432   tree (* merge_decl_attributes) (tree, tree);
 433
 434   /* Given two types, merge their attributes and return the result.  */
 435   tree (* merge_type_attributes) (tree, tree);
 436
 437   /* Table of machine attributes and functions to handle them.
 438      Ignored if NULL.  */
 439   const struct attribute_spec *attribute_table;
 440
 441   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 442      one if they are compatible and two if they are nearly compatible
 443      (which causes a warning to be generated).  */
 444   int (* comp_type_attributes) (tree type1, tree type2);
 445
 446   /* Assign default attributes to the newly defined TYPE.  */
 447   void (* set_default_type_attributes) (tree type);
 448
 449   /* Insert attributes on the newly created DECL.  */
 450   void (* insert_attributes) (tree decl, tree *attributes);
 451
 452   /* Return true if FNDECL (which has at least one machine attribute)
 453      can be inlined despite its machine attributes, false otherwise.  */
 454   bool (* function_attribute_inlinable_p) (tree fndecl);
 455
 456   /* Return true if bitfields in RECORD_TYPE should follow the
 457      Microsoft Visual C++ bitfield layout rules.  */
 458   bool (* ms_bitfield_layout_p) (tree record_type);
 459
 460   /* True if the target supports decimal floating point.  */
 461   bool (* decimal_float_supported_p) (void);
 462
 463   /* Return true if anonymous bitfields affect structure alignment.  */
 464   bool (* align_anon_bitfield) (void);
 465
 466   /* Return true if volatile bitfields should use the narrowest type possible.
 467      Return false if they should use the container type.  */
 468   bool (* narrow_volatile_bitfield) (void);
 469
 470   /* Set up target-specific built-in functions.  */
 471   void (* init_builtins) (void);
 472
 473   /* Expand a target-specific builtin.  */
 474   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 475                           enum machine_mode mode, int ignore);
 476
 477   /* Select a replacement for a target-specific builtin.  This is done
 478      *before* regular type checking, and so allows the target to implement
 479      a crude form of function overloading.  The result is a complete
 480      expression that implements the operation.  */
 481   tree (*resolve_overloaded_builtin) (tree decl, tree params);
 482
 483   /* Fold a target-specific builtin.  */
 484   tree (* fold_builtin) (tree fndecl, tree arglist, bool ignore);
 485
 486   /* For a vendor-specific fundamental TYPE, return a pointer to
 487      a statically-allocated string containing the C++ mangling for
 488      TYPE.  In all other cases, return NULL.  */
 489   const char * (* mangle_fundamental_type) (tree type);
 490
 491   /* Make any adjustments to libfunc names needed for this target.  */
 492   void (* init_libfuncs) (void);
 493
 494   /* Given a decl, a section name, and whether the decl initializer
 495      has relocs, choose attributes for the section.  */
 496   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 497   unsigned int (* section_type_flags) (tree, const char *, int);
 498
 499   /* True if new jumps cannot be created, to replace existing ones or
 500      not, at the current point in the compilation.  */
 501   bool (* cannot_modify_jumps_p) (void);
 502
 503   /* Return a register class for which branch target register
 504      optimizations should be applied.  */
 505   int (* branch_target_register_class) (void);
 506
 507   /* Return true if branch target register optimizations should include
 508      callee-saved registers that are not already live during the current
 509      function.  AFTER_PE_GEN is true if prologues and epilogues have
 510      already been generated.  */
 511   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 512
 513   /* True if the constant X cannot be placed in the constant pool.  */
 514   bool (* cannot_force_const_mem) (rtx);
 515
 516   /* True if the insn X cannot be duplicated.  */
 517   bool (* cannot_copy_insn_p) (rtx);
 518
 519   /* True if X is considered to be commutative.  */
 520   bool (* commutative_p) (rtx, int);
 521
 522   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 523   rtx (* delegitimize_address) (rtx);
 524
 525   /* True if the given constant can be put into an object_block.  */
 526   bool (* use_blocks_for_constant_p) (enum machine_mode, rtx);
 527
 528   /* The minimum and maximum byte offsets for anchored addresses.  */
 529   HOST_WIDE_INT min_anchor_offset;
 530   HOST_WIDE_INT max_anchor_offset;
 531
 532   /* True if section anchors can be used to access the given symbol.  */
 533   bool (* use_anchors_for_symbol_p) (rtx);
 534
 535   /* True if it is OK to do sibling call optimization for the specified
 536      call expression EXP.  DECL will be the called function, or NULL if
 537      this is an indirect call.  */
 538   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 539
 540   /* True if EXP should be placed in a "small data" section.  */
 541   bool (* in_small_data_p) (tree);
 542
 543   /* True if EXP names an object for which name resolution must resolve
 544      to the current module.  */
 545   bool (* binds_local_p) (tree);
 546
 547   /* Modify and return the identifier of a DECL's external name,
 548      originally identified by ID, as required by the target,
 549     (eg, append @nn to windows32 stdcall function names).
 550      The default is to return ID without modification. */
 551    tree (* mangle_decl_assembler_name) (tree decl, tree  id);
 552
 553   /* Do something target-specific to record properties of the DECL into
 554      the associated SYMBOL_REF.  */
 555   void (* encode_section_info) (tree, rtx, int);
 556
 557   /* Undo the effects of encode_section_info on the symbol string.  */
 558   const char * (* strip_name_encoding) (const char *);
 559
 560   /* If shift optabs for MODE are known to always truncate the shift count,
 561      return the mask that they apply.  Return 0 otherwise.  */
 562   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
 563
 564   /* Return the number of divisions in the given MODE that should be present,
 565      so that it is profitable to turn the division into a multiplication by
 566      the reciprocal.  */
 567   unsigned int (* min_divisions_for_recip_mul) (enum machine_mode mode);
 568
 569   /* If the representation of integral MODE is such that values are
 570      always sign-extended to a wider mode MODE_REP then return
 571      SIGN_EXTEND.  Return UNKNOWN otherwise.  */
 572   /* Note that the return type ought to be RTX_CODE, but that's not
 573      necessarily defined at this point.  */
 574   int (* mode_rep_extended) (enum machine_mode mode,
 575                              enum machine_mode mode_rep);
 576
 577   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 578   bool (* valid_pointer_mode) (enum machine_mode mode);
 579
 580   /* True if MODE is valid for the target.  By "valid", we mean able to
 581      be manipulated in non-trivial ways.  In particular, this means all
 582      the arithmetic is supported.  */
 583   bool (* scalar_mode_supported_p) (enum machine_mode mode);
 584
 585   /* Similarly for vector modes.  "Supported" here is less strict.  At
 586      least some operations are supported; need to check optabs or builtins
 587      for further details.  */
 588   bool (* vector_mode_supported_p) (enum machine_mode mode);
 589
 590   /* True if a vector is opaque.  */
 591   bool (* vector_opaque_p) (tree);
 592
 593   /* Compute a (partial) cost for rtx X.  Return true if the complete
 594      cost has been computed, and false if subexpressions should be
 595      scanned.  In either case, *TOTAL contains the cost result.  */
 596   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 597      not necessarily defined at this point.  */
 598   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 599
 600   /* Compute the cost of X, used as an address.  Never called with
 601      invalid addresses.  */
 602   int (* address_cost) (rtx x);
 603
 604   /* Return where to allocate pseudo for a given hard register initial
 605      value.  */
 606   rtx (* allocate_initial_value) (rtx x);
 607
 608   /* Given a register, this hook should return a parallel of registers
 609      to represent where to find the register pieces.  Define this hook
 610      if the register and its mode are represented in Dwarf in
 611      non-contiguous locations, or if the register should be
 612      represented in more than one register in Dwarf.  Otherwise, this
 613      hook should return NULL_RTX.  */
 614   rtx (* dwarf_register_span) (rtx);
 615
 616   /* If expand_builtin_init_dwarf_reg_sizes needs to fill in table
 617      entries not corresponding directly to registers below
 618      FIRST_PSEUDO_REGISTER, this hook should generate the necessary
 619      code, given the address of the table.  */
 620   void (* init_dwarf_reg_sizes_extra) (tree);
 621
 622   /* Fetch the fixed register(s) which hold condition codes, for
 623      targets where it makes sense to look for duplicate assignments to
 624      the condition codes.  This should return true if there is such a
 625      register, false otherwise.  The arguments should be set to the
 626      fixed register numbers.  Up to two condition code registers are
 627      supported.  If there is only one for this target, the int pointed
 628      at by the second argument should be set to -1.  */
 629   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 630
 631   /* If two condition code modes are compatible, return a condition
 632      code mode which is compatible with both, such that a comparison
 633      done in the returned mode will work for both of the original
 634      modes.  If the condition code modes are not compatible, return
 635      VOIDmode.  */
 636   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 637                                              enum machine_mode);
 638
 639   /* Do machine-dependent code transformations.  Called just before
 640      delayed-branch scheduling.  */
 641   void (* machine_dependent_reorg) (void);
 642
 643   /* Create the __builtin_va_list type.  */
 644   tree (* build_builtin_va_list) (void);
 645
 646   /* Gimplifies a VA_ARG_EXPR.  */
 647   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 648                                  tree *post_p);
 649
 650   /* Validity-checking routines for PCH files, target-specific.
 651      get_pch_validity returns a pointer to the data to be stored,
 652      and stores the size in its argument.  pch_valid_p gets the same
 653      information back and returns NULL if the PCH is valid,
 654      or an error message if not.
 655   */
 656   void * (* get_pch_validity) (size_t *);
 657   const char * (* pch_valid_p) (const void *, size_t);
 658
 659   /* If nonnull, this function checks whether a PCH file with the
 660      given set of target flags can be used.  It returns NULL if so,
 661      otherwise it returns an error message.  */
 662   const char *(*check_pch_target_flags) (int);
 663
 664   /* True if the compiler should give an enum type only as many
 665      bytes as it takes to represent the range of possible values of
 666      that type.  */
 667   bool (* default_short_enums) (void);
 668
 669   /* This target hook returns an rtx that is used to store the address
 670      of the current frame into the built-in setjmp buffer.  */
 671   rtx (* builtin_setjmp_frame_value) (void);
 672
 673   /* This target hook should add STRING_CST trees for any hard regs
 674      the port wishes to automatically clobber for an asm.  */
 675   tree (* md_asm_clobbers) (tree, tree, tree);
 676
 677   /* This target hook allows the backend to specify a calling convention
 678      in the debug information.  This function actually returns an
 679      enum dwarf_calling_convention, but because of forward declarations
 680      and not wanting to include dwarf2.h everywhere target.h is included
 681      the function is being declared as an int.  */
 682   int (* dwarf_calling_convention) (tree);
 683
 684   /* This target hook allows the backend to emit frame-related insns that
 685      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
 686      engine will invoke it on insns of the form
 687        (set (reg) (unspec [...] UNSPEC_INDEX))
 688      and
 689        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
 690      to let the backend emit the call frame instructions.  */
 691   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
 692
 693   /* Perform architecture specific checking of statements gimplified
 694      from VA_ARG_EXPR.  LHS is left hand side of MODIFY_EXPR, RHS
 695      is right hand side.  Returns true if the statements doesn't need
 696      to be checked for va_list references.  */
 697   bool (* stdarg_optimize_hook) (struct stdarg_info *ai, tree lhs, tree rhs);
 698
 699   /* This target hook allows the operating system to override the DECL
 700      that represents the external variable that contains the stack
 701      protection guard variable.  The type of this DECL is ptr_type_node.  */
 702   tree (* stack_protect_guard) (void);
 703
 704   /* This target hook allows the operating system to override the CALL_EXPR
 705      that is invoked when a check vs the guard variable fails.  */
 706   tree (* stack_protect_fail) (void);
 707
 708   /* Returns NULL if target supports the insn within a doloop block,
 709      otherwise it returns an error message.  */
 710   const char * (*invalid_within_doloop) (rtx);
 711
 712   /* DECL is a variable or function with __attribute__((dllimport))
 713      specified.  Use this hook if the target needs to add extra validation
 714      checks to  handle_dll_attribute ().  */
 715   bool (* valid_dllimport_attribute_p) (tree decl);
 716
 717   /* Functions relating to calls - argument passing, returns, etc.  */
 718   struct calls {
 719     bool (*promote_function_args) (tree fntype);
 720     bool (*promote_function_return) (tree fntype);
 721     bool (*promote_prototypes) (tree fntype);
 722     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 723     bool (*return_in_memory) (tree type, tree fndecl);
 724     bool (*return_in_msb) (tree type);
 725
 726     /* Return true if a parameter must be passed by reference.  TYPE may
 727        be null if this is a libcall.  CA may be null if this query is
 728        from __builtin_va_arg.  */
 729     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 730                                tree type, bool named_arg);
 731
 732     rtx (*expand_builtin_saveregs) (void);
 733     /* Returns pretend_argument_size.  */
 734     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 735                                     tree type, int *pretend_arg_size,
 736                                     int second_time);
 737     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 738     /* Returns true if we should use
 739        targetm.calls.setup_incoming_varargs() and/or
 740        targetm.calls.strict_argument_naming().  */
 741     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 742
 743     /* Given a complex type T, return true if a parameter of type T
 744        should be passed as two scalars.  */
 745     bool (* split_complex_arg) (tree type);
 746
 747     /* Return true if type T, mode MODE, may not be passed in registers,
 748        but must be passed on the stack.  */
 749     /* ??? This predicate should be applied strictly after pass-by-reference.
 750        Need audit to verify that this is the case.  */
 751     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 752
 753     /* Return true if type TYPE, mode MODE, which is passed by reference,
 754        should have the object copy generated by the callee rather than
 755        the caller.  It is never called for TYPE requiring constructors.  */
 756     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 757                             tree type, bool named);
 758
 759     /* Return zero for arguments passed entirely on the stack or entirely
 760        in registers.  If passed in both, return the number of bytes passed
 761        in registers; the balance is therefore passed on the stack.  */
 762     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 763                                tree type, bool named);
 764
 765     /* Return the diagnostic message string if function without a prototype
 766        is not allowed for this 'val' argument; NULL otherwise. */
 767     const char *(*invalid_arg_for_unprototyped_fn) (tree typelist,
 768                                                     tree funcdecl, tree val);
 769
 770     /* Return an rtx for the return value location of the function
 771        specified by FN_DECL_OR_TYPE with a return type of RET_TYPE.  */
 772     rtx (*function_value) (tree ret_type, tree fn_decl_or_type,
 773                            bool outgoing);
 774
 775     /* Return an rtx for the argument pointer incoming to the
 776        current function.  */
 777     rtx (*internal_arg_pointer) (void);
 778   } calls;
 779
 780   /* Return the diagnostic message string if conversion from FROMTYPE
 781      to TOTYPE is not allowed, NULL otherwise.  */
 782   const char *(*invalid_conversion) (tree fromtype, tree totype);
 783
 784   /* Return the diagnostic message string if the unary operation OP is
 785      not permitted on TYPE, NULL otherwise.  */
 786   const char *(*invalid_unary_op) (int op, tree type);
 787
 788   /* Return the diagnostic message string if the binary operation OP
 789      is not permitted on TYPE1 and TYPE2, NULL otherwise.  */
 790   const char *(*invalid_binary_op) (int op, tree type1, tree type2);
 791
 792   /* Return the class for a secondary reload, and fill in extra information.  */
 793   enum reg_class (*secondary_reload) (bool, rtx, enum reg_class,
 794                                       enum machine_mode,
 795                                       struct secondary_reload_info *);
 796
 797   /* Functions specific to the C++ frontend.  */
 798   struct cxx {
 799     /* Return the integer type used for guard variables.  */
 800     tree (*guard_type) (void);
 801     /* Return true if only the low bit of the guard should be tested.  */
 802     bool (*guard_mask_bit) (void);
 803     /* Returns the size of the array cookie for an array of type.  */
 804     tree (*get_cookie_size) (tree);
 805     /* Returns true if the element size should be stored in the
 806        array cookie.  */
 807     bool (*cookie_has_size) (void);
 808     /* Allows backends to perform additional processing when
 809        deciding if a class should be exported or imported.  */
 810     int (*import_export_class) (tree, int);
 811     /* Returns true if constructors and destructors return "this".  */
 812     bool (*cdtor_returns_this) (void);
 813     /* Returns true if the key method for a class can be an inline
 814        function, so long as it is not declared inline in the class
 815        itself.  Returning true is the behavior required by the Itanium
 816        C++ ABI.  */
 817     bool (*key_method_may_be_inline) (void);
 818     /* DECL is a virtual table, virtual table table, typeinfo object,
 819        or other similar implicit class data object that will be
 820        emitted with external linkage in this translation unit.  No ELF
 821        visibility has been explicitly specified.  If the target needs
 822        to specify a visibility other than that of the containing class,
 823        use this hook to set DECL_VISIBILITY and
 824        DECL_VISIBILITY_SPECIFIED.  */
 825     void (*determine_class_data_visibility) (tree decl);
 826     /* Returns true (the default) if virtual tables and other
 827        similar implicit class data objects are always COMDAT if they
 828        have external linkage.  If this hook returns false, then
 829        class data for classes whose virtual table will be emitted in
 830        only one translation unit will not be COMDAT.  */
 831     bool (*class_data_always_comdat) (void);
 832     /* Returns true (the default) if the RTTI for the basic types,
 833        which is always defined in the C++ runtime, should be COMDAT;
 834        false if it should not be COMDAT.  */
 835     bool (*library_rtti_comdat) (void);
 836     /* Returns true if __aeabi_atexit should be used to register static
 837        destructors.  */
 838     bool (*use_aeabi_atexit) (void);
 839     /* Returns true if target may use atexit in the same manner as
 840     __cxa_atexit  to register static destructors.  */
 841     bool (*use_atexit_for_cxa_atexit) (void);
 842     /* TYPE is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that
 843        has just been defined.  Use this hook to make adjustments to the
 844        class  (eg, tweak visibility or perform any other required
 845        target modifications).  */
 846     void (*adjust_class_at_definition) (tree type);
 847   } cxx;
 848
 849   /* For targets that need to mark extra registers as live on entry to
 850      the function, they should define this target hook and set their
 851      bits in the bitmap passed in. */
 852   void (*live_on_entry) (bitmap);
 853
 854   /* True if unwinding tables should be generated by default.  */
 855   bool unwind_tables_default;
 856
 857   /* Leave the boolean fields at the end.  */
 858
 859   /* True if arbitrary sections are supported.  */
 860   bool have_named_sections;
 861
 862   /* True if we can create zeroed data by switching to a BSS section
 863      and then using ASM_OUTPUT_SKIP to allocate the space.  */
 864   bool have_switchable_bss_sections;
 865
 866   /* True if "native" constructors and destructors are supported,
 867      false if we're using collect2 for the job.  */
 868   bool have_ctors_dtors;
 869
 870   /* True if thread-local storage is supported.  */
 871   bool have_tls;
 872
 873   /* True if a small readonly data section is supported.  */
 874   bool have_srodata_section;
 875
 876   /* True if EH frame info sections should be zero-terminated.  */
 877   bool terminate_dw2_eh_frame_info;
 878
 879   /* True if #NO_APP should be emitted at the beginning of
 880      assembly output.  */
 881   bool file_start_app_off;
 882
 883   /* True if output_file_directive should be called for main_input_filename
 884      at the beginning of assembly output.  */
 885   bool file_start_file_directive;
 886
 887   /* True if #pragma redefine_extname is to be supported.  */
 888   bool handle_pragma_redefine_extname;
 889
 890   /* True if #pragma extern_prefix is to be supported.  */
 891   bool handle_pragma_extern_prefix;
 892
 893   /* True if the target is allowed to reorder memory accesses unless
 894      synchronization is explicitly requested.  */
 895   bool relaxed_ordering;
 896
 897   /* Returns true if we should generate exception tables for use with the
 898      ARM EABI.  The effects the encoding of function exception specifications.
 899    */
 900   bool arm_eabi_unwinder;
 901
 902   /* Leave the boolean fields at the end.  */
 903 };
 904
 905 extern struct gcc_target targetm;
 906
 907 struct gcc_targetcm {
 908   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
 909      passed to the switch; it is NULL if no argument was.  VALUE is the
 910      value of ARG if CODE specifies a UInteger option, otherwise it is
 911      1 if the positive form of the switch was used and 0 if the negative
 912      form was.  Return true if the switch was valid.  */
 913   bool (*handle_c_option) (size_t code, const char *arg, int value);
 914 };
 915
 916 /* Each target can provide their own.  */
 917 extern struct gcc_targetcm targetcm;
 918
 919 #endif /* GCC_TARGET_H */