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   /* Returns a code for a target-specific builtin that implements
 487      reciprocal of the function, or NULL_TREE if not available.  */
 488   tree (* builtin_reciprocal) (unsigned, bool, bool);
 489
 490   /* For a vendor-specific fundamental TYPE, return a pointer to
 491      a statically-allocated string containing the C++ mangling for
 492      TYPE.  In all other cases, return NULL.  */
 493   const char * (* mangle_fundamental_type) (tree type);
 494
 495   /* Make any adjustments to libfunc names needed for this target.  */
 496   void (* init_libfuncs) (void);
 497
 498   /* Given a decl, a section name, and whether the decl initializer
 499      has relocs, choose attributes for the section.  */
 500   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 501   unsigned int (* section_type_flags) (tree, const char *, int);
 502
 503   /* True if new jumps cannot be created, to replace existing ones or
 504      not, at the current point in the compilation.  */
 505   bool (* cannot_modify_jumps_p) (void);
 506
 507   /* Return a register class for which branch target register
 508      optimizations should be applied.  */
 509   int (* branch_target_register_class) (void);
 510
 511   /* Return true if branch target register optimizations should include
 512      callee-saved registers that are not already live during the current
 513      function.  AFTER_PE_GEN is true if prologues and epilogues have
 514      already been generated.  */
 515   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 516
 517   /* True if the constant X cannot be placed in the constant pool.  */
 518   bool (* cannot_force_const_mem) (rtx);
 519
 520   /* True if the insn X cannot be duplicated.  */
 521   bool (* cannot_copy_insn_p) (rtx);
 522
 523   /* True if X is considered to be commutative.  */
 524   bool (* commutative_p) (rtx, int);
 525
 526   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 527   rtx (* delegitimize_address) (rtx);
 528
 529   /* True if the given constant can be put into an object_block.  */
 530   bool (* use_blocks_for_constant_p) (enum machine_mode, rtx);
 531
 532   /* The minimum and maximum byte offsets for anchored addresses.  */
 533   HOST_WIDE_INT min_anchor_offset;
 534   HOST_WIDE_INT max_anchor_offset;
 535
 536   /* True if section anchors can be used to access the given symbol.  */
 537   bool (* use_anchors_for_symbol_p) (rtx);
 538
 539   /* True if it is OK to do sibling call optimization for the specified
 540      call expression EXP.  DECL will be the called function, or NULL if
 541      this is an indirect call.  */
 542   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 543
 544   /* True if EXP should be placed in a "small data" section.  */
 545   bool (* in_small_data_p) (tree);
 546
 547   /* True if EXP names an object for which name resolution must resolve
 548      to the current module.  */
 549   bool (* binds_local_p) (tree);
 550
 551   /* Modify and return the identifier of a DECL's external name,
 552      originally identified by ID, as required by the target,
 553     (eg, append @nn to windows32 stdcall function names).
 554      The default is to return ID without modification. */
 555    tree (* mangle_decl_assembler_name) (tree decl, tree  id);
 556
 557   /* Do something target-specific to record properties of the DECL into
 558      the associated SYMBOL_REF.  */
 559   void (* encode_section_info) (tree, rtx, int);
 560
 561   /* Undo the effects of encode_section_info on the symbol string.  */
 562   const char * (* strip_name_encoding) (const char *);
 563
 564   /* If shift optabs for MODE are known to always truncate the shift count,
 565      return the mask that they apply.  Return 0 otherwise.  */
 566   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
 567
 568   /* Return the number of divisions in the given MODE that should be present,
 569      so that it is profitable to turn the division into a multiplication by
 570      the reciprocal.  */
 571   unsigned int (* min_divisions_for_recip_mul) (enum machine_mode mode);
 572
 573   /* If the representation of integral MODE is such that values are
 574      always sign-extended to a wider mode MODE_REP then return
 575      SIGN_EXTEND.  Return UNKNOWN otherwise.  */
 576   /* Note that the return type ought to be RTX_CODE, but that's not
 577      necessarily defined at this point.  */
 578   int (* mode_rep_extended) (enum machine_mode mode,
 579                              enum machine_mode mode_rep);
 580
 581   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 582   bool (* valid_pointer_mode) (enum machine_mode mode);
 583
 584   /* True if MODE is valid for the target.  By "valid", we mean able to
 585      be manipulated in non-trivial ways.  In particular, this means all
 586      the arithmetic is supported.  */
 587   bool (* scalar_mode_supported_p) (enum machine_mode mode);
 588
 589   /* Similarly for vector modes.  "Supported" here is less strict.  At
 590      least some operations are supported; need to check optabs or builtins
 591      for further details.  */
 592   bool (* vector_mode_supported_p) (enum machine_mode mode);
 593
 594   /* True if a vector is opaque.  */
 595   bool (* vector_opaque_p) (tree);
 596
 597   /* Compute a (partial) cost for rtx X.  Return true if the complete
 598      cost has been computed, and false if subexpressions should be
 599      scanned.  In either case, *TOTAL contains the cost result.  */
 600   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 601      not necessarily defined at this point.  */
 602   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 603
 604   /* Compute the cost of X, used as an address.  Never called with
 605      invalid addresses.  */
 606   int (* address_cost) (rtx x);
 607
 608   /* Return where to allocate pseudo for a given hard register initial
 609      value.  */
 610   rtx (* allocate_initial_value) (rtx x);
 611
 612   /* Given a register, this hook should return a parallel of registers
 613      to represent where to find the register pieces.  Define this hook
 614      if the register and its mode are represented in Dwarf in
 615      non-contiguous locations, or if the register should be
 616      represented in more than one register in Dwarf.  Otherwise, this
 617      hook should return NULL_RTX.  */
 618   rtx (* dwarf_register_span) (rtx);
 619
 620   /* If expand_builtin_init_dwarf_reg_sizes needs to fill in table
 621      entries not corresponding directly to registers below
 622      FIRST_PSEUDO_REGISTER, this hook should generate the necessary
 623      code, given the address of the table.  */
 624   void (* init_dwarf_reg_sizes_extra) (tree);
 625
 626   /* Fetch the fixed register(s) which hold condition codes, for
 627      targets where it makes sense to look for duplicate assignments to
 628      the condition codes.  This should return true if there is such a
 629      register, false otherwise.  The arguments should be set to the
 630      fixed register numbers.  Up to two condition code registers are
 631      supported.  If there is only one for this target, the int pointed
 632      at by the second argument should be set to -1.  */
 633   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 634
 635   /* If two condition code modes are compatible, return a condition
 636      code mode which is compatible with both, such that a comparison
 637      done in the returned mode will work for both of the original
 638      modes.  If the condition code modes are not compatible, return
 639      VOIDmode.  */
 640   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 641                                              enum machine_mode);
 642
 643   /* Do machine-dependent code transformations.  Called just before
 644      delayed-branch scheduling.  */
 645   void (* machine_dependent_reorg) (void);
 646
 647   /* Create the __builtin_va_list type.  */
 648   tree (* build_builtin_va_list) (void);
 649
 650   /* Gimplifies a VA_ARG_EXPR.  */
 651   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 652                                  tree *post_p);
 653
 654   /* Validity-checking routines for PCH files, target-specific.
 655      get_pch_validity returns a pointer to the data to be stored,
 656      and stores the size in its argument.  pch_valid_p gets the same
 657      information back and returns NULL if the PCH is valid,
 658      or an error message if not.
 659   */
 660   void * (* get_pch_validity) (size_t *);
 661   const char * (* pch_valid_p) (const void *, size_t);
 662
 663   /* If nonnull, this function checks whether a PCH file with the
 664      given set of target flags can be used.  It returns NULL if so,
 665      otherwise it returns an error message.  */
 666   const char *(*check_pch_target_flags) (int);
 667
 668   /* True if the compiler should give an enum type only as many
 669      bytes as it takes to represent the range of possible values of
 670      that type.  */
 671   bool (* default_short_enums) (void);
 672
 673   /* This target hook returns an rtx that is used to store the address
 674      of the current frame into the built-in setjmp buffer.  */
 675   rtx (* builtin_setjmp_frame_value) (void);
 676
 677   /* This target hook should add STRING_CST trees for any hard regs
 678      the port wishes to automatically clobber for an asm.  */
 679   tree (* md_asm_clobbers) (tree, tree, tree);
 680
 681   /* This target hook allows the backend to specify a calling convention
 682      in the debug information.  This function actually returns an
 683      enum dwarf_calling_convention, but because of forward declarations
 684      and not wanting to include dwarf2.h everywhere target.h is included
 685      the function is being declared as an int.  */
 686   int (* dwarf_calling_convention) (tree);
 687
 688   /* This target hook allows the backend to emit frame-related insns that
 689      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
 690      engine will invoke it on insns of the form
 691        (set (reg) (unspec [...] UNSPEC_INDEX))
 692      and
 693        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
 694      to let the backend emit the call frame instructions.  */
 695   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
 696
 697   /* Perform architecture specific checking of statements gimplified
 698      from VA_ARG_EXPR.  LHS is left hand side of MODIFY_EXPR, RHS
 699      is right hand side.  Returns true if the statements doesn't need
 700      to be checked for va_list references.  */
 701   bool (* stdarg_optimize_hook) (struct stdarg_info *ai, tree lhs, tree rhs);
 702
 703   /* This target hook allows the operating system to override the DECL
 704      that represents the external variable that contains the stack
 705      protection guard variable.  The type of this DECL is ptr_type_node.  */
 706   tree (* stack_protect_guard) (void);
 707
 708   /* This target hook allows the operating system to override the CALL_EXPR
 709      that is invoked when a check vs the guard variable fails.  */
 710   tree (* stack_protect_fail) (void);
 711
 712   /* Returns NULL if target supports the insn within a doloop block,
 713      otherwise it returns an error message.  */
 714   const char * (*invalid_within_doloop) (rtx);
 715
 716   /* DECL is a variable or function with __attribute__((dllimport))
 717      specified.  Use this hook if the target needs to add extra validation
 718      checks to  handle_dll_attribute ().  */
 719   bool (* valid_dllimport_attribute_p) (tree decl);
 720
 721   /* Functions relating to calls - argument passing, returns, etc.  */
 722   struct calls {
 723     bool (*promote_function_args) (tree fntype);
 724     bool (*promote_function_return) (tree fntype);
 725     bool (*promote_prototypes) (tree fntype);
 726     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 727     bool (*return_in_memory) (tree type, tree fndecl);
 728     bool (*return_in_msb) (tree type);
 729
 730     /* Return true if a parameter must be passed by reference.  TYPE may
 731        be null if this is a libcall.  CA may be null if this query is
 732        from __builtin_va_arg.  */
 733     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 734                                tree type, bool named_arg);
 735
 736     rtx (*expand_builtin_saveregs) (void);
 737     /* Returns pretend_argument_size.  */
 738     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 739                                     tree type, int *pretend_arg_size,
 740                                     int second_time);
 741     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 742     /* Returns true if we should use
 743        targetm.calls.setup_incoming_varargs() and/or
 744        targetm.calls.strict_argument_naming().  */
 745     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 746
 747     /* Given a complex type T, return true if a parameter of type T
 748        should be passed as two scalars.  */
 749     bool (* split_complex_arg) (tree type);
 750
 751     /* Return true if type T, mode MODE, may not be passed in registers,
 752        but must be passed on the stack.  */
 753     /* ??? This predicate should be applied strictly after pass-by-reference.
 754        Need audit to verify that this is the case.  */
 755     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 756
 757     /* Return true if type TYPE, mode MODE, which is passed by reference,
 758        should have the object copy generated by the callee rather than
 759        the caller.  It is never called for TYPE requiring constructors.  */
 760     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 761                             tree type, bool named);
 762
 763     /* Return zero for arguments passed entirely on the stack or entirely
 764        in registers.  If passed in both, return the number of bytes passed
 765        in registers; the balance is therefore passed on the stack.  */
 766     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 767                                tree type, bool named);
 768
 769     /* Return the diagnostic message string if function without a prototype
 770        is not allowed for this 'val' argument; NULL otherwise. */
 771     const char *(*invalid_arg_for_unprototyped_fn) (tree typelist,
 772                                                     tree funcdecl, tree val);
 773
 774     /* Return an rtx for the return value location of the function
 775        specified by FN_DECL_OR_TYPE with a return type of RET_TYPE.  */
 776     rtx (*function_value) (tree ret_type, tree fn_decl_or_type,
 777                            bool outgoing);
 778
 779     /* Return an rtx for the argument pointer incoming to the
 780        current function.  */
 781     rtx (*internal_arg_pointer) (void);
 782   } calls;
 783
 784   /* Return the diagnostic message string if conversion from FROMTYPE
 785      to TOTYPE is not allowed, NULL otherwise.  */
 786   const char *(*invalid_conversion) (tree fromtype, tree totype);
 787
 788   /* Return the diagnostic message string if the unary operation OP is
 789      not permitted on TYPE, NULL otherwise.  */
 790   const char *(*invalid_unary_op) (int op, tree type);
 791
 792   /* Return the diagnostic message string if the binary operation OP
 793      is not permitted on TYPE1 and TYPE2, NULL otherwise.  */
 794   const char *(*invalid_binary_op) (int op, tree type1, tree type2);
 795
 796   /* Return the class for a secondary reload, and fill in extra information.  */
 797   enum reg_class (*secondary_reload) (bool, rtx, enum reg_class,
 798                                       enum machine_mode,
 799                                       struct secondary_reload_info *);
 800
 801   /* Functions specific to the C++ frontend.  */
 802   struct cxx {
 803     /* Return the integer type used for guard variables.  */
 804     tree (*guard_type) (void);
 805     /* Return true if only the low bit of the guard should be tested.  */
 806     bool (*guard_mask_bit) (void);
 807     /* Returns the size of the array cookie for an array of type.  */
 808     tree (*get_cookie_size) (tree);
 809     /* Returns true if the element size should be stored in the
 810        array cookie.  */
 811     bool (*cookie_has_size) (void);
 812     /* Allows backends to perform additional processing when
 813        deciding if a class should be exported or imported.  */
 814     int (*import_export_class) (tree, int);
 815     /* Returns true if constructors and destructors return "this".  */
 816     bool (*cdtor_returns_this) (void);
 817     /* Returns true if the key method for a class can be an inline
 818        function, so long as it is not declared inline in the class
 819        itself.  Returning true is the behavior required by the Itanium
 820        C++ ABI.  */
 821     bool (*key_method_may_be_inline) (void);
 822     /* DECL is a virtual table, virtual table table, typeinfo object,
 823        or other similar implicit class data object that will be
 824        emitted with external linkage in this translation unit.  No ELF
 825        visibility has been explicitly specified.  If the target needs
 826        to specify a visibility other than that of the containing class,
 827        use this hook to set DECL_VISIBILITY and
 828        DECL_VISIBILITY_SPECIFIED.  */
 829     void (*determine_class_data_visibility) (tree decl);
 830     /* Returns true (the default) if virtual tables and other
 831        similar implicit class data objects are always COMDAT if they
 832        have external linkage.  If this hook returns false, then
 833        class data for classes whose virtual table will be emitted in
 834        only one translation unit will not be COMDAT.  */
 835     bool (*class_data_always_comdat) (void);
 836     /* Returns true (the default) if the RTTI for the basic types,
 837        which is always defined in the C++ runtime, should be COMDAT;
 838        false if it should not be COMDAT.  */
 839     bool (*library_rtti_comdat) (void);
 840     /* Returns true if __aeabi_atexit should be used to register static
 841        destructors.  */
 842     bool (*use_aeabi_atexit) (void);
 843     /* Returns true if target may use atexit in the same manner as
 844     __cxa_atexit  to register static destructors.  */
 845     bool (*use_atexit_for_cxa_atexit) (void);
 846     /* TYPE is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that
 847        has just been defined.  Use this hook to make adjustments to the
 848        class  (eg, tweak visibility or perform any other required
 849        target modifications).  */
 850     void (*adjust_class_at_definition) (tree type);
 851   } cxx;
 852
 853   /* For targets that need to mark extra registers as live on entry to
 854      the function, they should define this target hook and set their
 855      bits in the bitmap passed in. */
 856   void (*live_on_entry) (bitmap);
 857
 858   /* True if unwinding tables should be generated by default.  */
 859   bool unwind_tables_default;
 860
 861   /* Leave the boolean fields at the end.  */
 862
 863   /* True if arbitrary sections are supported.  */
 864   bool have_named_sections;
 865
 866   /* True if we can create zeroed data by switching to a BSS section
 867      and then using ASM_OUTPUT_SKIP to allocate the space.  */
 868   bool have_switchable_bss_sections;
 869
 870   /* True if "native" constructors and destructors are supported,
 871      false if we're using collect2 for the job.  */
 872   bool have_ctors_dtors;
 873
 874   /* True if thread-local storage is supported.  */
 875   bool have_tls;
 876
 877   /* True if a small readonly data section is supported.  */
 878   bool have_srodata_section;
 879
 880   /* True if EH frame info sections should be zero-terminated.  */
 881   bool terminate_dw2_eh_frame_info;
 882
 883   /* True if #NO_APP should be emitted at the beginning of
 884      assembly output.  */
 885   bool file_start_app_off;
 886
 887   /* True if output_file_directive should be called for main_input_filename
 888      at the beginning of assembly output.  */
 889   bool file_start_file_directive;
 890
 891   /* True if #pragma redefine_extname is to be supported.  */
 892   bool handle_pragma_redefine_extname;
 893
 894   /* True if #pragma extern_prefix is to be supported.  */
 895   bool handle_pragma_extern_prefix;
 896
 897   /* True if the target is allowed to reorder memory accesses unless
 898      synchronization is explicitly requested.  */
 899   bool relaxed_ordering;
 900
 901   /* Returns true if we should generate exception tables for use with the
 902      ARM EABI.  The effects the encoding of function exception specifications.
 903    */
 904   bool arm_eabi_unwinder;
 905
 906   /* Leave the boolean fields at the end.  */
 907 };
 908
 909 extern struct gcc_target targetm;
 910
 911 struct gcc_targetcm {
 912   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
 913      passed to the switch; it is NULL if no argument was.  VALUE is the
 914      value of ARG if CODE specifies a UInteger option, otherwise it is
 915      1 if the positive form of the switch was used and 0 if the negative
 916      form was.  Return true if the switch was valid.  */
 917   bool (*handle_c_option) (size_t code, const char *arg, int value);
 918 };
 919
 920 /* Each target can provide their own.  */
 921 extern struct gcc_targetcm targetcm;
 922
 923 #endif /* GCC_TARGET_H */