gcc/target.h

   1 /* Data structure definitions for a generic GCC target.
   2    Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
   3
   4 This program is free software; you can redistribute it and/or modify it
   5 under the terms of the GNU General Public License as published by the
   6 Free Software Foundation; either version 2, or (at your option) any
   7 later version.
   8
   9 This program is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 GNU General Public License for more details.
  13
  14 You should have received a copy of the GNU General Public License
  15 along with this program; if not, write to the Free Software
  16 Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17
  18  In other words, you are welcome to use, share and improve this program.
  19  You are forbidden to forbid anyone else to use, share and improve
  20  what you give them.   Help stamp out software-hoarding!  */
  21
  22 /* This file contains a data structure that describes a GCC target.
  23    At present it is incomplete, but in future it should grow to
  24    contain most or all target machine and target O/S specific
  25    information.
  26
  27    This structure has its initializer declared in target-def.h in the
  28    form of large macro TARGET_INITIALIZER that expands to many smaller
  29    macros.
  30
  31    The smaller macros each initialize one component of the structure,
  32    and each has a default.  Each target should have a file that
  33    includes target.h and target-def.h, and overrides any inappropriate
  34    defaults by undefining the relevant macro and defining a suitable
  35    replacement.  That file should then contain the definition of
  36    "targetm" like so:
  37
  38    struct gcc_target targetm = TARGET_INITIALIZER;
  39
  40    Doing things this way allows us to bring together everything that
  41    defines a GCC target.  By supplying a default that is appropriate
  42    to most targets, we can easily add new items without needing to
  43    edit dozens of target configuration files.  It should also allow us
  44    to gradually reduce the amount of conditional compilation that is
  45    scattered throughout GCC.  */
  46
  47 #ifndef GCC_TARGET_H
  48 #define GCC_TARGET_H
  49
  50 #include "tm.h"
  51 #include "insn-modes.h"
  52
  53 struct gcc_target
  54 {
  55   /* Functions that output assembler for the target.  */
  56   struct asm_out
  57   {
  58     /* Opening and closing parentheses for asm expression grouping.  */
  59     const char *open_paren, *close_paren;
  60
  61     /* Assembler instructions for creating various kinds of integer object.  */
  62     const char *byte_op;
  63     struct asm_int_op
  64     {
  65       const char *hi;
  66       const char *si;
  67       const char *di;
  68       const char *ti;
  69     } aligned_op, unaligned_op;
  70
  71     /* Try to output the assembler code for an integer object whose
  72        value is given by X.  SIZE is the size of the object in bytes and
  73        ALIGNED_P indicates whether it is aligned.  Return true if
  74        successful.  Only handles cases for which BYTE_OP, ALIGNED_OP
  75        and UNALIGNED_OP are NULL.  */
  76     bool (* integer) (rtx x, unsigned int size, int aligned_p);
  77
  78     /* Output code that will globalize a label.  */
  79     void (* globalize_label) (FILE *, const char *);
  80
  81     /* Output code that will emit a label for unwind info, if this
  82        target requires such labels.  Second argument is the decl the
  83        unwind info is associated with, third is a boolean: true if
  84        this is for exception handling, fourth is a boolean: true if
  85        this is only a placeholder for an omitted FDE.  */
  86     void (* unwind_label) (FILE *, tree, int, int);
  87
  88     /* Emit any directives required to unwind this instruction.  */
  89     void (* unwind_emit) (FILE *, rtx);
  90
  91     /* Output an internal label.  */
  92     void (* internal_label) (FILE *, const char *, unsigned long);
  93
  94     /* Emit an assembler directive to set visibility for the symbol
  95        associated with the tree decl.  */
  96     void (* visibility) (tree, int);
  97
  98     /* Output the assembler code for entry to a function.  */
  99     void (* function_prologue) (FILE *, HOST_WIDE_INT);
 100
 101     /* Output the assembler code for end of prologue.  */
 102     void (* function_end_prologue) (FILE *);
 103
 104     /* Output the assembler code for start of epilogue.  */
 105     void (* function_begin_epilogue) (FILE *);
 106
 107     /* Output the assembler code for function exit.  */
 108     void (* function_epilogue) (FILE *, HOST_WIDE_INT);
 109
 110     /* Switch to an arbitrary section NAME with attributes as
 111        specified by FLAGS.  */
 112     void (* named_section) (const char *, unsigned int);
 113
 114     /* Switch to the section that holds the exception table.  */
 115     void (* exception_section) (void);
 116
 117     /* Switch to the section that holds the exception frames.  */
 118     void (* eh_frame_section) (void);
 119
 120     /* Select and switch to a section for EXP.  It may be a DECL or a
 121        constant.  RELOC is nonzero if runtime relocations must be applied;
 122        bit 1 will be set if the runtime relocations require non-local
 123        name resolution.  ALIGN is the required alignment of the data.  */
 124     void (* select_section) (tree, int, unsigned HOST_WIDE_INT);
 125
 126     /* Select and switch to a section for X with MODE.  ALIGN is
 127        the desired alignment of the data.  */
 128     void (* select_rtx_section) (enum machine_mode, rtx,
 129                                  unsigned HOST_WIDE_INT);
 130
 131     /* Select a unique section name for DECL.  RELOC is the same as
 132        for SELECT_SECTION.  */
 133     void (* unique_section) (tree, int);
 134
 135     /* Tell assembler to switch to the readonly data section associated
 136        with function DECL.  */
 137     void (* function_rodata_section) (tree);
 138
 139     /* Output a constructor for a symbol with a given priority.  */
 140     void (* constructor) (rtx, int);
 141
 142     /* Output a destructor for a symbol with a given priority.  */
 143     void (* destructor) (rtx, int);
 144
 145     /* Output the assembler code for a thunk function.  THUNK_DECL is the
 146        declaration for the thunk function itself, FUNCTION is the decl for
 147        the target function.  DELTA is an immediate constant offset to be
 148        added to THIS.  If VCALL_OFFSET is nonzero, the word at
 149        *(*this + vcall_offset) should be added to THIS.  */
 150     void (* output_mi_thunk) (FILE *file, tree thunk_decl,
 151                               HOST_WIDE_INT delta, HOST_WIDE_INT vcall_offset,
 152                               tree function_decl);
 153
 154     /* Determine whether output_mi_thunk would succeed.  */
 155     /* ??? Ideally, this hook would not exist, and success or failure
 156        would be returned from output_mi_thunk directly.  But there's
 157        too much undo-able setup involved in invoking output_mi_thunk.
 158        Could be fixed by making output_mi_thunk emit rtl instead of
 159        text to the output file.  */
 160     bool (* can_output_mi_thunk) (tree thunk_decl, HOST_WIDE_INT delta,
 161                                   HOST_WIDE_INT vcall_offset,
 162                                   tree function_decl);
 163
 164     /* Output any boilerplate text needed at the beginning of a
 165        translation unit.  */
 166     void (*file_start) (void);
 167
 168     /* Output any boilerplate text needed at the end of a
 169        translation unit.  */
 170     void (*file_end) (void);
 171
 172     /* Output an assembler pseudo-op to declare a library function name
 173        external.  */
 174     void (*external_libcall) (rtx);
 175
 176      /* Output an assembler directive to mark decl live. This instructs
 177         linker to not dead code strip this symbol.  */
 178     void (*mark_decl_preserved) (const char *);
 179
 180   } asm_out;
 181
 182   /* Functions relating to instruction scheduling.  */
 183   struct sched
 184   {
 185     /* Given the current cost, COST, of an insn, INSN, calculate and
 186        return a new cost based on its relationship to DEP_INSN through
 187        the dependence LINK.  The default is to make no adjustment.  */
 188     int (* adjust_cost) (rtx insn, rtx link, rtx def_insn, int cost);
 189
 190     /* Adjust the priority of an insn as you see fit.  Returns the new
 191        priority.  */
 192     int (* adjust_priority) (rtx, int);
 193
 194     /* Function which returns the maximum number of insns that can be
 195        scheduled in the same machine cycle.  This must be constant
 196        over an entire compilation.  The default is 1.  */
 197     int (* issue_rate) (void);
 198
 199     /* Calculate how much this insn affects how many more insns we
 200        can emit this cycle.  Default is they all cost the same.  */
 201     int (* variable_issue) (FILE *, int, rtx, int);
 202
 203     /* Initialize machine-dependent scheduling code.  */
 204     void (* md_init) (FILE *, int, int);
 205
 206     /* Finalize machine-dependent scheduling code.  */
 207     void (* md_finish) (FILE *, int);
 208
 209     /* Initialize machine-dependent function while scheduling code.  */
 210     void (* md_init_global) (FILE *, int, int);
 211
 212     /* Finalize machine-dependent function wide scheduling code.  */
 213     void (* md_finish_global) (FILE *, int);
 214
 215     /* Reorder insns in a machine-dependent fashion, in two different
 216        places.  Default does nothing.  */
 217     int (* reorder) (FILE *, int, rtx *, int *, int);
 218     int (* reorder2) (FILE *, int, rtx *, int *, int);
 219
 220     /* The following member value is a pointer to a function called
 221        after evaluation forward dependencies of insns in chain given
 222        by two parameter values (head and tail correspondingly).  */
 223     void (* dependencies_evaluation_hook) (rtx, rtx);
 224
 225     /* The values of the following four members are pointers to
 226        functions used to simplify the automaton descriptions.
 227        dfa_pre_cycle_insn and dfa_post_cycle_insn give functions
 228        returning insns which are used to change the pipeline hazard
 229        recognizer state when the new simulated processor cycle
 230        correspondingly starts and finishes.  The function defined by
 231        init_dfa_pre_cycle_insn and init_dfa_post_cycle_insn are used
 232        to initialize the corresponding insns.  The default values of
 233        the members result in not changing the automaton state when
 234        the new simulated processor cycle correspondingly starts and
 235        finishes.  */
 236     void (* init_dfa_pre_cycle_insn) (void);
 237     rtx (* dfa_pre_cycle_insn) (void);
 238     void (* init_dfa_post_cycle_insn) (void);
 239     rtx (* dfa_post_cycle_insn) (void);
 240
 241     /* The following member value is a pointer to a function returning value
 242        which defines how many insns in queue `ready' will we try for
 243        multi-pass scheduling.  If the member value is nonzero and the
 244        function returns positive value, the DFA based scheduler will make
 245        multi-pass scheduling for the first cycle.  In other words, we will
 246        try to choose ready insn which permits to start maximum number of
 247        insns on the same cycle.  */
 248     int (* first_cycle_multipass_dfa_lookahead) (void);
 249
 250     /* The following member value is pointer to a function controlling
 251        what insns from the ready insn queue will be considered for the
 252        multipass insn scheduling.  If the hook returns zero for insn
 253        passed as the parameter, the insn will be not chosen to be
 254        issued.  */
 255     int (* first_cycle_multipass_dfa_lookahead_guard) (rtx);
 256
 257     /* The following member value is pointer to a function called by
 258        the insn scheduler before issuing insn passed as the third
 259        parameter on given cycle.  If the hook returns nonzero, the
 260        insn is not issued on given processors cycle.  Instead of that,
 261        the processor cycle is advanced.  If the value passed through
 262        the last parameter is zero, the insn ready queue is not sorted
 263        on the new cycle start as usually.  The first parameter passes
 264        file for debugging output.  The second one passes the scheduler
 265        verbose level of the debugging output.  The forth and the fifth
 266        parameter values are correspondingly processor cycle on which
 267        the previous insn has been issued and the current processor
 268        cycle.  */
 269     int (* dfa_new_cycle) (FILE *, int, rtx, int, int, int *);
 270
 271     /* The following member value is a pointer to a function called
 272        by the insn scheduler.  It should return true if there exists a
 273        dependence which is considered costly by the target, between
 274        the insn passed as the first parameter, and the insn passed as
 275        the second parameter.  The third parameter is the INSN_DEPEND
 276        link that represents the dependence between the two insns.  The
 277        fourth argument is the cost of the dependence as estimated by
 278        the scheduler.  The last argument is the distance in cycles
 279        between the already scheduled insn (first parameter) and the
 280        the second insn (second parameter).  */
 281     bool (* is_costly_dependence) (rtx, rtx, rtx, int, int);
 282   } sched;
 283
 284   /* Return machine mode for filter value. */
 285   enum machine_mode (* eh_return_filter_mode) (void);
 286
 287   /* Given two decls, merge their attributes and return the result.  */
 288   tree (* merge_decl_attributes) (tree, tree);
 289
 290   /* Given two types, merge their attributes and return the result.  */
 291   tree (* merge_type_attributes) (tree, tree);
 292
 293   /* Table of machine attributes and functions to handle them.
 294      Ignored if NULL.  */
 295   const struct attribute_spec *attribute_table;
 296
 297   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 298      one if they are compatible and two if they are nearly compatible
 299      (which causes a warning to be generated).  */
 300   int (* comp_type_attributes) (tree type1, tree type2);
 301
 302   /* Assign default attributes to the newly defined TYPE.  */
 303   void (* set_default_type_attributes) (tree type);
 304
 305   /* Insert attributes on the newly created DECL.  */
 306   void (* insert_attributes) (tree decl, tree *attributes);
 307
 308   /* Return true if FNDECL (which has at least one machine attribute)
 309      can be inlined despite its machine attributes, false otherwise.  */
 310   bool (* function_attribute_inlinable_p) (tree fndecl);
 311
 312   /* Return true if bitfields in RECORD_TYPE should follow the
 313      Microsoft Visual C++ bitfield layout rules.  */
 314   bool (* ms_bitfield_layout_p) (tree record_type);
 315
 316   /* Return true if anonymous bitfields affect structure alignment.  */
 317   bool (* align_anon_bitfield) (void);
 318
 319   /* Set up target-specific built-in functions.  */
 320   void (* init_builtins) (void);
 321
 322   /* Expand a target-specific builtin.  */
 323   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 324                           enum machine_mode mode, int ignore);
 325
 326   /* For a vendor-specific fundamental TYPE, return a pointer to
 327      a statically-allocated string containing the C++ mangling for
 328      TYPE.  In all other cases, return NULL.  */
 329   const char * (* mangle_fundamental_type) (tree type);
 330
 331   /* Make any adjustments to libfunc names needed for this target.  */
 332   void (* init_libfuncs) (void);
 333
 334   /* Given a decl, a section name, and whether the decl initializer
 335      has relocs, choose attributes for the section.  */
 336   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 337   unsigned int (* section_type_flags) (tree, const char *, int);
 338
 339   /* True if new jumps cannot be created, to replace existing ones or
 340      not, at the current point in the compilation.  */
 341   bool (* cannot_modify_jumps_p) (void);
 342
 343   /* Return a register class for which branch target register
 344      optimizations should be applied.  */
 345   int (* branch_target_register_class) (void);
 346
 347   /* Return true if branch target register optimizations should include
 348      callee-saved registers that are not already live during the current
 349      function.  AFTER_PE_GEN is true if prologues and epilogues have
 350      already been generated.  */
 351   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 352
 353   /* True if the constant X cannot be placed in the constant pool.  */
 354   bool (* cannot_force_const_mem) (rtx);
 355
 356   /* True if the insn X cannot be duplicated.  */
 357   bool (* cannot_copy_insn_p) (rtx);
 358
 359   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 360   rtx (* delegitimize_address) (rtx);
 361
 362   /* True if it is OK to do sibling call optimization for the specified
 363      call expression EXP.  DECL will be the called function, or NULL if
 364      this is an indirect call.  */
 365   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 366
 367   /* True if EXP should be placed in a "small data" section.  */
 368   bool (* in_small_data_p) (tree);
 369
 370   /* True if EXP names an object for which name resolution must resolve
 371      to the current module.  */
 372   bool (* binds_local_p) (tree);
 373
 374   /* Do something target-specific to record properties of the DECL into
 375      the associated SYMBOL_REF.  */
 376   void (* encode_section_info) (tree, rtx, int);
 377
 378   /* Undo the effects of encode_section_info on the symbol string.  */
 379   const char * (* strip_name_encoding) (const char *);
 380
 381   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 382   bool (* valid_pointer_mode) (enum machine_mode mode);
 383
 384   /* True if MODE is valid for a vector.  */
 385   bool (* vector_mode_supported_p) (enum machine_mode mode);
 386
 387   /* True if a vector is opaque.  */
 388   bool (* vector_opaque_p) (tree);
 389
 390   /* Compute a (partial) cost for rtx X.  Return true if the complete
 391      cost has been computed, and false if subexpressions should be
 392      scanned.  In either case, *TOTAL contains the cost result.  */
 393   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 394      not necessarily defined at this point.  */
 395   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 396
 397   /* Compute the cost of X, used as an address.  Never called with
 398      invalid addresses.  */
 399   int (* address_cost) (rtx x);
 400
 401   /* Given a register, this hook should return a parallel of registers
 402      to represent where to find the register pieces.  Define this hook
 403      if the register and its mode are represented in Dwarf in
 404      non-contiguous locations, or if the register should be
 405      represented in more than one register in Dwarf.  Otherwise, this
 406      hook should return NULL_RTX.  */
 407   rtx (* dwarf_register_span) (rtx);
 408
 409   /* Fetch the fixed register(s) which hold condition codes, for
 410      targets where it makes sense to look for duplicate assignments to
 411      the condition codes.  This should return true if there is such a
 412      register, false otherwise.  The arguments should be set to the
 413      fixed register numbers.  Up to two condition code registers are
 414      supported.  If there is only one for this target, the int pointed
 415      at by the second argument should be set to -1.  */
 416   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 417
 418   /* If two condition code modes are compatible, return a condition
 419      code mode which is compatible with both, such that a comparison
 420      done in the returned mode will work for both of the original
 421      modes.  If the condition code modes are not compatible, return
 422      VOIDmode.  */
 423   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 424                                              enum machine_mode);
 425
 426   /* Do machine-dependent code transformations.  Called just before
 427      delayed-branch scheduling.  */
 428   void (* machine_dependent_reorg) (void);
 429
 430   /* Create the __builtin_va_list type.  */
 431   tree (* build_builtin_va_list) (void);
 432
 433   /* Gimplifies a VA_ARG_EXPR.  */
 434   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 435                                  tree *post_p);
 436
 437   /* Validity-checking routines for PCH files, target-specific.
 438      get_pch_validity returns a pointer to the data to be stored,
 439      and stores the size in its argument.  pch_valid_p gets the same
 440      information back and returns NULL if the PCH is valid,
 441      or an error message if not.
 442   */
 443   void * (* get_pch_validity) (size_t *);
 444   const char * (* pch_valid_p) (const void *, size_t);
 445
 446   /* True if the compiler should give an enum type only as many
 447      bytes as it takes to represent the range of possible values of
 448      that type.  */
 449   bool (* default_short_enums) (void);
 450
 451   /* This target hook returns an rtx that is used to store the address
 452      of the current frame into the built-in setjmp buffer.  */
 453   rtx (* builtin_setjmp_frame_value) (void);
 454
 455   /* This target hook should add STRING_CST trees for any hard regs
 456      the port wishes to automatically clobber for all asms.  */
 457   tree (* md_asm_clobbers) (tree);
 458
 459   /* Functions relating to calls - argument passing, returns, etc.  */
 460   struct calls {
 461     bool (*promote_function_args) (tree fntype);
 462     bool (*promote_function_return) (tree fntype);
 463     bool (*promote_prototypes) (tree fntype);
 464     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 465     bool (*return_in_memory) (tree type, tree fndecl);
 466     bool (*return_in_msb) (tree type);
 467
 468     /* Return true if a parameter must be passed by reference.  TYPE may
 469        be null if this is a libcall.  CA may be null if this query is
 470        from __builtin_va_arg.  */
 471     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 472                                tree type, bool named_arg);
 473
 474     rtx (*expand_builtin_saveregs) (void);
 475     /* Returns pretend_argument_size.  */
 476     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 477                                     tree type, int *pretend_arg_size,
 478                                     int second_time);
 479     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 480     /* Returns true if we should use
 481        targetm.calls.setup_incoming_varargs() and/or
 482        targetm.calls.strict_argument_naming().  */
 483     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 484
 485     /* Given a complex type T, return true if a parameter of type T
 486        should be passed as two scalars.  */
 487     bool (* split_complex_arg) (tree type);
 488
 489     /* Return true if type T, mode MODE, may not be passed in registers,
 490        but must be passed on the stack.  */
 491     /* ??? This predicate should be applied strictly after pass-by-reference.
 492        Need audit to verify that this is the case.  */
 493     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 494   } calls;
 495
 496   /* Functions specific to the C++ frontend.  */
 497   struct cxx {
 498     /* Return the integer type used for guard variables.  */
 499     tree (*guard_type) (void);
 500     /* Return true if only the low bit of the guard should be tested.  */
 501     bool (*guard_mask_bit) (void);
 502     /* Returns the size of the array cookie for an array of type.  */
 503     tree (*get_cookie_size) (tree);
 504     /* Returns true if the element size should be stored in the
 505        array cookie.  */
 506     bool (*cookie_has_size) (void);
 507     /* Allows backends to perform additional processing when
 508        deciding if a class should be exported or imported.  */
 509     int (*import_export_class) (tree, int);
 510     /* Returns true if constructors and destructors return "this".  */
 511     bool (*cdtor_returns_this) (void);
 512   } cxx;
 513
 514   /* Leave the boolean fields at the end.  */
 515
 516   /* True if arbitrary sections are supported.  */
 517   bool have_named_sections;
 518
 519   /* True if "native" constructors and destructors are supported,
 520      false if we're using collect2 for the job.  */
 521   bool have_ctors_dtors;
 522
 523   /* True if thread-local storage is supported.  */
 524   bool have_tls;
 525
 526   /* True if a small readonly data section is supported.  */
 527   bool have_srodata_section;
 528
 529   /* True if EH frame info sections should be zero-terminated.  */
 530   bool terminate_dw2_eh_frame_info;
 531
 532   /* True if #NO_APP should be emitted at the beginning of
 533      assembly output.  */
 534   bool file_start_app_off;
 535
 536   /* True if output_file_directive should be called for main_input_filename
 537      at the beginning of assembly output.  */
 538   bool file_start_file_directive;
 539
 540   /* True if #pragma redefine_extname is to be supported.  */
 541   bool handle_pragma_redefine_extname;
 542
 543   /* True if #pragma extern_prefix is to be supported.  */
 544   bool handle_pragma_extern_prefix;
 545
 546   /* True if the RTL prologue and epilogue should be expanded after all
 547      passes that modify the instructions (and not merely reorder them)
 548      have been run.  */
 549   bool late_rtl_prologue_epilogue;
 550
 551   /* Leave the boolean fields at the end.  */
 552 };
 553
 554 extern struct gcc_target targetm;
 555
 556 #endif /* GCC_TARGET_H */