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