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   } asm_out;
 176
 177   /* Functions relating to instruction scheduling.  */
 178   struct sched
 179   {
 180     /* Given the current cost, COST, of an insn, INSN, calculate and
 181        return a new cost based on its relationship to DEP_INSN through
 182        the dependence LINK.  The default is to make no adjustment.  */
 183     int (* adjust_cost) (rtx insn, rtx link, rtx def_insn, int cost);
 184
 185     /* Adjust the priority of an insn as you see fit.  Returns the new
 186        priority.  */
 187     int (* adjust_priority) (rtx, int);
 188
 189     /* Function which returns the maximum number of insns that can be
 190        scheduled in the same machine cycle.  This must be constant
 191        over an entire compilation.  The default is 1.  */
 192     int (* issue_rate) (void);
 193
 194     /* Calculate how much this insn affects how many more insns we
 195        can emit this cycle.  Default is they all cost the same.  */
 196     int (* variable_issue) (FILE *, int, rtx, int);
 197
 198     /* Initialize machine-dependent scheduling code.  */
 199     void (* md_init) (FILE *, int, int);
 200
 201     /* Finalize machine-dependent scheduling code.  */
 202     void (* md_finish) (FILE *, int);
 203
 204     /* Initialize machine-dependent function while scheduling code.  */
 205     void (* md_init_global) (FILE *, int, int);
 206
 207     /* Finalize machine-dependent function wide scheduling code.  */
 208     void (* md_finish_global) (FILE *, int);
 209
 210     /* Reorder insns in a machine-dependent fashion, in two different
 211        places.  Default does nothing.  */
 212     int (* reorder) (FILE *, int, rtx *, int *, int);
 213     int (* reorder2) (FILE *, int, rtx *, int *, int);
 214
 215     /* The following member value is a pointer to a function called
 216        after evaluation forward dependencies of insns in chain given
 217        by two parameter values (head and tail correspondingly).  */
 218     void (* dependencies_evaluation_hook) (rtx, rtx);
 219
 220     /* The values of the following four members are pointers to
 221        functions used to simplify the automaton descriptions.
 222        dfa_pre_cycle_insn and dfa_post_cycle_insn give functions
 223        returning insns which are used to change the pipeline hazard
 224        recognizer state when the new simulated processor cycle
 225        correspondingly starts and finishes.  The function defined by
 226        init_dfa_pre_cycle_insn and init_dfa_post_cycle_insn are used
 227        to initialize the corresponding insns.  The default values of
 228        the members result in not changing the automaton state when
 229        the new simulated processor cycle correspondingly starts and
 230        finishes.  */
 231     void (* init_dfa_pre_cycle_insn) (void);
 232     rtx (* dfa_pre_cycle_insn) (void);
 233     void (* init_dfa_post_cycle_insn) (void);
 234     rtx (* dfa_post_cycle_insn) (void);
 235
 236     /* The following member value is a pointer to a function returning value
 237        which defines how many insns in queue `ready' will we try for
 238        multi-pass scheduling.  If the member value is nonzero and the
 239        function returns positive value, the DFA based scheduler will make
 240        multi-pass scheduling for the first cycle.  In other words, we will
 241        try to choose ready insn which permits to start maximum number of
 242        insns on the same cycle.  */
 243     int (* first_cycle_multipass_dfa_lookahead) (void);
 244
 245     /* The following member value is pointer to a function controlling
 246        what insns from the ready insn queue will be considered for the
 247        multipass insn scheduling.  If the hook returns zero for insn
 248        passed as the parameter, the insn will be not chosen to be
 249        issued.  */
 250     int (* first_cycle_multipass_dfa_lookahead_guard) (rtx);
 251
 252     /* The following member value is pointer to a function called by
 253        the insn scheduler before issuing insn passed as the third
 254        parameter on given cycle.  If the hook returns nonzero, the
 255        insn is not issued on given processors cycle.  Instead of that,
 256        the processor cycle is advanced.  If the value passed through
 257        the last parameter is zero, the insn ready queue is not sorted
 258        on the new cycle start as usually.  The first parameter passes
 259        file for debugging output.  The second one passes the scheduler
 260        verbose level of the debugging output.  The forth and the fifth
 261        parameter values are correspondingly processor cycle on which
 262        the previous insn has been issued and the current processor
 263        cycle.  */
 264     int (* dfa_new_cycle) (FILE *, int, rtx, int, int, int *);
 265
 266     /* The following member value is a pointer to a function called
 267        by the insn scheduler.  It should return true if there exists a
 268        dependence which is considered costly by the target, between
 269        the insn passed as the first parameter, and the insn passed as
 270        the second parameter.  The third parameter is the INSN_DEPEND
 271        link that represents the dependence between the two insns.  The
 272        fourth argument is the cost of the dependence as estimated by
 273        the scheduler.  The last argument is the distance in cycles
 274        between the already scheduled insn (first parameter) and the
 275        the second insn (second parameter).  */
 276     bool (* is_costly_dependence) (rtx, rtx, rtx, int, int);
 277   } sched;
 278
 279   /* Given two decls, merge their attributes and return the result.  */
 280   tree (* merge_decl_attributes) (tree, tree);
 281
 282   /* Given two types, merge their attributes and return the result.  */
 283   tree (* merge_type_attributes) (tree, tree);
 284
 285   /* Table of machine attributes and functions to handle them.
 286      Ignored if NULL.  */
 287   const struct attribute_spec *attribute_table;
 288
 289   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
 290      one if they are compatible and two if they are nearly compatible
 291      (which causes a warning to be generated).  */
 292   int (* comp_type_attributes) (tree type1, tree type2);
 293
 294   /* Assign default attributes to the newly defined TYPE.  */
 295   void (* set_default_type_attributes) (tree type);
 296
 297   /* Insert attributes on the newly created DECL.  */
 298   void (* insert_attributes) (tree decl, tree *attributes);
 299
 300   /* Return true if FNDECL (which has at least one machine attribute)
 301      can be inlined despite its machine attributes, false otherwise.  */
 302   bool (* function_attribute_inlinable_p) (tree fndecl);
 303
 304   /* Return true if bitfields in RECORD_TYPE should follow the
 305      Microsoft Visual C++ bitfield layout rules.  */
 306   bool (* ms_bitfield_layout_p) (tree record_type);
 307
 308   /* Return true if anonymous bitfields affect structure alignment.  */
 309   bool (* align_anon_bitfield) (void);
 310
 311   /* Set up target-specific built-in functions.  */
 312   void (* init_builtins) (void);
 313
 314   /* Expand a target-specific builtin.  */
 315   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
 316                           enum machine_mode mode, int ignore);
 317
 318   /* For a vendor-specific fundamental TYPE, return a pointer to
 319      a statically-allocated string containing the C++ mangling for
 320      TYPE.  In all other cases, return NULL.  */
 321   const char * (* mangle_fundamental_type) (tree type);
 322
 323   /* Make any adjustments to libfunc names needed for this target.  */
 324   void (* init_libfuncs) (void);
 325
 326   /* Given a decl, a section name, and whether the decl initializer
 327      has relocs, choose attributes for the section.  */
 328   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
 329   unsigned int (* section_type_flags) (tree, const char *, int);
 330
 331   /* True if new jumps cannot be created, to replace existing ones or
 332      not, at the current point in the compilation.  */
 333   bool (* cannot_modify_jumps_p) (void);
 334
 335   /* Return a register class for which branch target register
 336      optimizations should be applied.  */
 337   int (* branch_target_register_class) (void);
 338
 339   /* Return true if branch target register optimizations should include
 340      callee-saved registers that are not already live during the current
 341      function.  AFTER_PE_GEN is true if prologues and epilogues have
 342      already been generated.  */
 343   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
 344
 345   /* True if the constant X cannot be placed in the constant pool.  */
 346   bool (* cannot_force_const_mem) (rtx);
 347
 348   /* True if the insn X cannot be duplicated.  */
 349   bool (* cannot_copy_insn_p) (rtx);
 350
 351   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
 352   rtx (* delegitimize_address) (rtx);
 353
 354   /* True if it is OK to do sibling call optimization for the specified
 355      call expression EXP.  DECL will be the called function, or NULL if
 356      this is an indirect call.  */
 357   bool (*function_ok_for_sibcall) (tree decl, tree exp);
 358
 359   /* True if EXP should be placed in a "small data" section.  */
 360   bool (* in_small_data_p) (tree);
 361
 362   /* True if EXP names an object for which name resolution must resolve
 363      to the current module.  */
 364   bool (* binds_local_p) (tree);
 365
 366   /* Do something target-specific to record properties of the DECL into
 367      the associated SYMBOL_REF.  */
 368   void (* encode_section_info) (tree, rtx, int);
 369
 370   /* Undo the effects of encode_section_info on the symbol string.  */
 371   const char * (* strip_name_encoding) (const char *);
 372
 373   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
 374   bool (* valid_pointer_mode) (enum machine_mode mode);
 375
 376   /* True if a vector is opaque.  */
 377   bool (* vector_opaque_p) (tree);
 378
 379   /* Compute a (partial) cost for rtx X.  Return true if the complete
 380      cost has been computed, and false if subexpressions should be
 381      scanned.  In either case, *TOTAL contains the cost result.  */
 382   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
 383      not necessarily defined at this point.  */
 384   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
 385
 386   /* Compute the cost of X, used as an address.  Never called with
 387      invalid addresses.  */
 388   int (* address_cost) (rtx x);
 389
 390   /* Given a register, this hook should return a parallel of registers
 391      to represent where to find the register pieces.  Define this hook
 392      if the register and its mode are represented in Dwarf in
 393      non-contiguous locations, or if the register should be
 394      represented in more than one register in Dwarf.  Otherwise, this
 395      hook should return NULL_RTX.  */
 396   rtx (* dwarf_register_span) (rtx);
 397
 398   /* Fetch the fixed register(s) which hold condition codes, for
 399      targets where it makes sense to look for duplicate assignments to
 400      the condition codes.  This should return true if there is such a
 401      register, false otherwise.  The arguments should be set to the
 402      fixed register numbers.  Up to two condition code registers are
 403      supported.  If there is only one for this target, the int pointed
 404      at by the second argument should be set to -1.  */
 405   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
 406
 407   /* If two condition code modes are compatible, return a condition
 408      code mode which is compatible with both, such that a comparison
 409      done in the returned mode will work for both of the original
 410      modes.  If the condition code modes are not compatible, return
 411      VOIDmode.  */
 412   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
 413                                              enum machine_mode);
 414
 415   /* Do machine-dependent code transformations.  Called just before
 416      delayed-branch scheduling.  */
 417   void (* machine_dependent_reorg) (void);
 418
 419   /* Create the __builtin_va_list type.  */
 420   tree (* build_builtin_va_list) (void);
 421
 422   /* Gimplifies a VA_ARG_EXPR.  */
 423   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
 424                                  tree *post_p);
 425
 426   /* Validity-checking routines for PCH files, target-specific.
 427      get_pch_validity returns a pointer to the data to be stored,
 428      and stores the size in its argument.  pch_valid_p gets the same
 429      information back and returns NULL if the PCH is valid,
 430      or an error message if not.
 431   */
 432   void * (* get_pch_validity) (size_t *);
 433   const char * (* pch_valid_p) (const void *, size_t);
 434
 435   /* True if the compiler should give an enum type only as many
 436      bytes as it takes to represent the range of possible values of
 437      that type.  */
 438   bool (* default_short_enums) (void);
 439
 440   /* This target hook returns an rtx that is used to store the address
 441      of the current frame into the built-in setjmp buffer.  */
 442   rtx (* builtin_setjmp_frame_value) (void);
 443
 444   /* This target hook should add STRING_CST trees for any hard regs
 445      the port wishes to automatically clobber for all asms.  */
 446   tree (* md_asm_clobbers) (tree);
 447
 448   /* Functions relating to calls - argument passing, returns, etc.  */
 449   struct calls {
 450     bool (*promote_function_args) (tree fntype);
 451     bool (*promote_function_return) (tree fntype);
 452     bool (*promote_prototypes) (tree fntype);
 453     rtx (*struct_value_rtx) (tree fndecl, int incoming);
 454     bool (*return_in_memory) (tree type, tree fndecl);
 455     bool (*return_in_msb) (tree type);
 456
 457     /* Return true if a parameter must be passed by reference.  TYPE may
 458        be null if this is a libcall.  CA may be null if this query is
 459        from __builtin_va_arg.  */
 460     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 461                                tree type, bool named_arg);
 462
 463     rtx (*expand_builtin_saveregs) (void);
 464     /* Returns pretend_argument_size.  */
 465     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
 466                                     tree type, int *pretend_arg_size,
 467                                     int second_time);
 468     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
 469     /* Returns true if we should use
 470        targetm.calls.setup_incoming_varargs() and/or
 471        targetm.calls.strict_argument_naming().  */
 472     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
 473
 474     /* Given a complex type T, return true if a parameter of type T
 475        should be passed as two scalars.  */
 476     bool (* split_complex_arg) (tree type);
 477
 478     /* Return true if type T, mode MODE, may not be passed in registers,
 479        but must be passed on the stack.  */
 480     /* ??? This predicate should be applied strictly after pass-by-reference.
 481        Need audit to verify that this is the case.  */
 482     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
 483   } calls;
 484
 485   /* Functions specific to the C++ frontend.  */
 486   struct cxx {
 487     /* Return the integer type used for guard variables.  */
 488     tree (*guard_type) (void);
 489     /* Return true if only the low bit of the guard should be tested.  */
 490     bool (*guard_mask_bit) (void);
 491     /* Returns the size of the array cookie for an array of type.  */
 492     tree (*get_cookie_size) (tree);
 493     /* Returns true if the element size should be stored in the
 494        array cookie.  */
 495     bool (*cookie_has_size) (void);
 496     /* Allows backends to perform additional processing when
 497        deciding if a class should be exported or imported.  */
 498     int (*import_export_class) (tree, int);
 499     /* Returns true if constructors and destructors return "this".  */
 500     bool (*cdtor_returns_this) (void);
 501   } cxx;
 502
 503   /* Leave the boolean fields at the end.  */
 504
 505   /* True if arbitrary sections are supported.  */
 506   bool have_named_sections;
 507
 508   /* True if "native" constructors and destructors are supported,
 509      false if we're using collect2 for the job.  */
 510   bool have_ctors_dtors;
 511
 512   /* True if thread-local storage is supported.  */
 513   bool have_tls;
 514
 515   /* True if a small readonly data section is supported.  */
 516   bool have_srodata_section;
 517
 518   /* True if EH frame info sections should be zero-terminated.  */
 519   bool terminate_dw2_eh_frame_info;
 520
 521   /* True if #NO_APP should be emitted at the beginning of
 522      assembly output.  */
 523   bool file_start_app_off;
 524
 525   /* True if output_file_directive should be called for main_input_filename
 526      at the beginning of assembly output.  */
 527   bool file_start_file_directive;
 528
 529   /* True if #pragma redefine_extname is to be supported.  */
 530   bool handle_pragma_redefine_extname;
 531
 532   /* True if #pragma extern_prefix is to be supported.  */
 533   bool handle_pragma_extern_prefix;
 534
 535   /* True if the RTL prologue and epilogue should be expanded after all
 536      passes that modify the instructions (and not merely reorder them)
 537      have been run.  */
 538   bool late_rtl_prologue_epilogue;
 539
 540   /* Leave the boolean fields at the end.  */
 541 };
 542
 543 extern struct gcc_target targetm;
 544
 545 #endif /* GCC_TARGET_H */