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概要[]

実装[]

 55 struct gcc_target
 56 {
 57   /* Functions that output assembler for the target.  */
 58   struct asm_out
 59   {
 60     /* Opening and closing parentheses for asm expression grouping.  */
 61     const char *open_paren, *close_paren;
 62 
 63     /* Assembler instructions for creating various kinds of integer object.  */
 64     const char *byte_op;
 65     struct asm_int_op
 66     {
 67       const char *hi;
 68       const char *si;
 69       const char *di;
 70       const char *ti;
 71     } aligned_op, unaligned_op;
 72 
 73     /* Try to output the assembler code for an integer object whose
 74        value is given by X.  SIZE is the size of the object in bytes and
 75        ALIGNED_P indicates whether it is aligned.  Return true if
 76        successful.  Only handles cases for which BYTE_OP, ALIGNED_OP
 77        and UNALIGNED_OP are NULL.  */
 78     bool (* integer) (rtx x, unsigned int size, int aligned_p);
 79 
 80     /* Output code that will globalize a label.  */
 81     void (* globalize_label) (FILE *, const char *);
 82 
 83     /* Output code that will emit a label for unwind info, if this
 84        target requires such labels.  Second argument is the decl the
 85        unwind info is associated with, third is a boolean: true if
 86        this is for exception handling, fourth is a boolean: true if
 87        this is only a placeholder for an omitted FDE.  */
 88     void (* unwind_label) (FILE *, tree, int, int);
 89 
 90     /* Emit any directives required to unwind this instruction.  */
 91     void (* unwind_emit) (FILE *, rtx);
 92 
 93     /* Output an internal label.  */
 94     void (* internal_label) (FILE *, const char *, unsigned long);
 95 
 96     /* Emit a ttype table reference to a typeinfo object.  */
 97     bool (* ttype) (rtx);
 98 
 99     /* Emit an assembler directive to set visibility for the symbol
100        associated with the tree decl.  */
101     void (* visibility) (tree, int);
102 
103     /* Output the assembler code for entry to a function.  */
104     void (* function_prologue) (FILE *, HOST_WIDE_INT);
105 
106     /* Output the assembler code for end of prologue.  */
107     void (* function_end_prologue) (FILE *);
108 
109     /* Output the assembler code for start of epilogue.  */
110     void (* function_begin_epilogue) (FILE *);
111 
112     /* Output the assembler code for function exit.  */
113     void (* function_epilogue) (FILE *, HOST_WIDE_INT);
114 
115     /* Tell assembler to change to section NAME with attributes FLAGS.
116        If DECL is non-NULL, it is the VAR_DECL or FUNCTION_DECL with
117        which this section is associated.  */
118     void (* named_section) (const char *name, unsigned int flags, tree decl);
119 
120     /* Switch to the section that holds the exception table.  */
121     void (* exception_section) (void);
122 
123     /* Switch to the section that holds the exception frames.  */
124     void (* eh_frame_section) (void);
125 
126     /* Select and switch to a section for EXP.  It may be a DECL or a
127        constant.  RELOC is nonzero if runtime relocations must be applied;
128        bit 1 will be set if the runtime relocations require non-local
129        name resolution.  ALIGN is the required alignment of the data.  */
130     void (* select_section) (tree, int, unsigned HOST_WIDE_INT);
131 
132     /* Select and switch to a section for X with MODE.  ALIGN is
133        the desired alignment of the data.  */
134     void (* select_rtx_section) (enum machine_mode, rtx,
135                                  unsigned HOST_WIDE_INT);
136 
137     /* Select a unique section name for DECL.  RELOC is the same as
138        for SELECT_SECTION.  */
139     void (* unique_section) (tree, int);
140 
141     /* Tell assembler to switch to the readonly data section associated
142        with function DECL.  */
143     void (* function_rodata_section) (tree);
144 
145     /* Output a constructor for a symbol with a given priority.  */
146     void (* constructor) (rtx, int);
147 
148     /* Output a destructor for a symbol with a given priority.  */
149     void (* destructor) (rtx, int);
150 
151     /* Output the assembler code for a thunk function.  THUNK_DECL is the
152        declaration for the thunk function itself, FUNCTION is the decl for
153        the target function.  DELTA is an immediate constant offset to be
154        added to THIS.  If VCALL_OFFSET is nonzero, the word at
155        *(*this + vcall_offset) should be added to THIS.  */
156     void (* output_mi_thunk) (FILE *file, tree thunk_decl,
157                               HOST_WIDE_INT delta, HOST_WIDE_INT vcall_offset,
158                               tree function_decl);
159 
160     /* Determine whether output_mi_thunk would succeed.  */
161     /* ??? Ideally, this hook would not exist, and success or failure
162        would be returned from output_mi_thunk directly.  But there's
163        too much undo-able setup involved in invoking output_mi_thunk.
164        Could be fixed by making output_mi_thunk emit rtl instead of
165        text to the output file.  */
166     bool (* can_output_mi_thunk) (tree thunk_decl, HOST_WIDE_INT delta,
167                                   HOST_WIDE_INT vcall_offset,
168                                   tree function_decl);
169 
170     /* Output any boilerplate text needed at the beginning of a
171        translation unit.  */
172     void (*file_start) (void);
173 
174     /* Output any boilerplate text needed at the end of a
175        translation unit.  */
176     void (*file_end) (void);
177 
178     /* Output an assembler pseudo-op to declare a library function name
179        external.  */
180     void (*external_libcall) (rtx);
181 
182      /* Output an assembler directive to mark decl live. This instructs
183         linker to not dead code strip this symbol.  */
184     void (*mark_decl_preserved) (const char *);
185 
186     /* Output a DTP-relative reference to a TLS symbol.  */
187     void (*output_dwarf_dtprel) (FILE *file, int size, rtx x);
188 
189   } asm_out;
190 
191   /* Functions relating to instruction scheduling.  */
192   struct sched
193   {
194     /* Given the current cost, COST, of an insn, INSN, calculate and
195        return a new cost based on its relationship to DEP_INSN through
196        the dependence LINK.  The default is to make no adjustment.  */
197     int (* adjust_cost) (rtx insn, rtx link, rtx def_insn, int cost);
198 
199     /* Adjust the priority of an insn as you see fit.  Returns the new
200        priority.  */
201     int (* adjust_priority) (rtx, int);
202 
203     /* Function which returns the maximum number of insns that can be
204        scheduled in the same machine cycle.  This must be constant
205        over an entire compilation.  The default is 1.  */
206     int (* issue_rate) (void);
207 
208     /* Calculate how much this insn affects how many more insns we
209        can emit this cycle.  Default is they all cost the same.  */
210     int (* variable_issue) (FILE *, int, rtx, int);
211 
212     /* Initialize machine-dependent scheduling code.  */
213     void (* md_init) (FILE *, int, int);
214 
215     /* Finalize machine-dependent scheduling code.  */
216     void (* md_finish) (FILE *, int);
217 
218     /* Initialize machine-dependent function while scheduling code.  */
219     void (* md_init_global) (FILE *, int, int);
220 
221     /* Finalize machine-dependent function wide scheduling code.  */
222     void (* md_finish_global) (FILE *, int);
223 
224     /* Reorder insns in a machine-dependent fashion, in two different
225        places.  Default does nothing.  */
226     int (* reorder) (FILE *, int, rtx *, int *, int);
227     int (* reorder2) (FILE *, int, rtx *, int *, int);
228 
229     /* The following member value is a pointer to a function called
230        after evaluation forward dependencies of insns in chain given
231        by two parameter values (head and tail correspondingly).  */
232     void (* dependencies_evaluation_hook) (rtx, rtx);
233 
234     /* The values of the following four members are pointers to
235        functions used to simplify the automaton descriptions.
236        dfa_pre_cycle_insn and dfa_post_cycle_insn give functions
237        returning insns which are used to change the pipeline hazard
238        recognizer state when the new simulated processor cycle
239        correspondingly starts and finishes.  The function defined by
240        init_dfa_pre_cycle_insn and init_dfa_post_cycle_insn are used
241        to initialize the corresponding insns.  The default values of
242        the members result in not changing the automaton state when
243        the new simulated processor cycle correspondingly starts and
244        finishes.  */
245     void (* init_dfa_pre_cycle_insn) (void);
246     rtx (* dfa_pre_cycle_insn) (void);
247     void (* init_dfa_post_cycle_insn) (void);
248     rtx (* dfa_post_cycle_insn) (void);
249 
250     /* The following member value is a pointer to a function returning value
251        which defines how many insns in queue `ready' will we try for
252        multi-pass scheduling.  If the member value is nonzero and the
253        function returns positive value, the DFA based scheduler will make
254        multi-pass scheduling for the first cycle.  In other words, we will
255        try to choose ready insn which permits to start maximum number of
256        insns on the same cycle.  */
257     int (* first_cycle_multipass_dfa_lookahead) (void);
258 
259     /* The following member value is pointer to a function controlling
260        what insns from the ready insn queue will be considered for the
261        multipass insn scheduling.  If the hook returns zero for insn
262        passed as the parameter, the insn will be not chosen to be
263        issued.  */
264     int (* first_cycle_multipass_dfa_lookahead_guard) (rtx);
265 
266     /* The following member value is pointer to a function called by
267        the insn scheduler before issuing insn passed as the third
268        parameter on given cycle.  If the hook returns nonzero, the
269        insn is not issued on given processors cycle.  Instead of that,
270        the processor cycle is advanced.  If the value passed through
271        the last parameter is zero, the insn ready queue is not sorted
272        on the new cycle start as usually.  The first parameter passes
273        file for debugging output.  The second one passes the scheduler
274        verbose level of the debugging output.  The forth and the fifth
275        parameter values are correspondingly processor cycle on which
276        the previous insn has been issued and the current processor
277        cycle.  */
278     int (* dfa_new_cycle) (FILE *, int, rtx, int, int, int *);
279 
280     /* The following member value is a pointer to a function called
281        by the insn scheduler.  It should return true if there exists a
282        dependence which is considered costly by the target, between
283        the insn passed as the first parameter, and the insn passed as
284        the second parameter.  The third parameter is the INSN_DEPEND
285        link that represents the dependence between the two insns.  The
286        fourth argument is the cost of the dependence as estimated by
287        the scheduler.  The last argument is the distance in cycles
288        between the already scheduled insn (first parameter) and the
289        the second insn (second parameter).  */
290     bool (* is_costly_dependence) (rtx, rtx, rtx, int, int);
291   } sched;
292 
293   /* Functions relating to vectorization.  */
294   struct vectorize
295   {
296     /* The following member value is a pointer to a function called
297        by the vectorizer, and return the decl of the target builtin
298        function.  */
299     tree (* builtin_mask_for_load) (void);
300   } vectorize;
301 
302   /* The initial value of target_flags.  */
303   int default_target_flags;
304 
305   /* Handle target switch CODE (an OPT_* value).  ARG is the argument
306      passed to the switch; it is NULL if no argument was.  VALUE is the
307      value of ARG if CODE specifies a UInteger option, otherwise it is
308      1 if the positive form of the switch was used and 0 if the negative
309      form was.  Return true if the switch was valid.  */
310   bool (* handle_option) (size_t code, const char *arg, int value);
311 
312   /* Return machine mode for filter value.  */
313   enum machine_mode (* eh_return_filter_mode) (void);
314 
315   /* Given two decls, merge their attributes and return the result.  */
316   tree (* merge_decl_attributes) (tree, tree);
317 
318   /* Given two types, merge their attributes and return the result.  */
319   tree (* merge_type_attributes) (tree, tree);
320 
321   /* Table of machine attributes and functions to handle them.
322      Ignored if NULL.  */
323   const struct attribute_spec *attribute_table;
324 
325   /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
326      one if they are compatible and two if they are nearly compatible
327      (which causes a warning to be generated).  */
328   int (* comp_type_attributes) (tree type1, tree type2);
329 
330   /* Assign default attributes to the newly defined TYPE.  */
331   void (* set_default_type_attributes) (tree type);
332 
333   /* Insert attributes on the newly created DECL.  */
334   void (* insert_attributes) (tree decl, tree *attributes);
335 
336   /* Return true if FNDECL (which has at least one machine attribute)
337      can be inlined despite its machine attributes, false otherwise.  */
338   bool (* function_attribute_inlinable_p) (tree fndecl);
339 
340   /* Return true if bitfields in RECORD_TYPE should follow the
341      Microsoft Visual C++ bitfield layout rules.  */
342   bool (* ms_bitfield_layout_p) (tree record_type);
343 
344   /* Return true if anonymous bitfields affect structure alignment.  */
345   bool (* align_anon_bitfield) (void);
346 
347   /* Set up target-specific built-in functions.  */
348   void (* init_builtins) (void);
349 
350   /* Expand a target-specific builtin.  */
351   rtx (* expand_builtin) (tree exp, rtx target, rtx subtarget,
352                           enum machine_mode mode, int ignore);
353 
354   /* Select a replacement for a target-specific builtin.  This is done
355      *before* regular type checking, and so allows the target to implement
356      a crude form of function overloading.  The result is a complete
357      expression that implements the operation.  */
358   tree (*resolve_overloaded_builtin) (tree decl, tree params);
359 
360   /* Fold a target-specific builtin.  */
361   tree (* fold_builtin) (tree fndecl, tree arglist, bool ignore);
362   
363   /* For a vendor-specific fundamental TYPE, return a pointer to
364      a statically-allocated string containing the C++ mangling for
365      TYPE.  In all other cases, return NULL.  */
366   const char * (* mangle_fundamental_type) (tree type);
367 
368   /* Make any adjustments to libfunc names needed for this target.  */
369   void (* init_libfuncs) (void);
370 
371   /* Given a decl, a section name, and whether the decl initializer
372      has relocs, choose attributes for the section.  */
373   /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
374   unsigned int (* section_type_flags) (tree, const char *, int);
375 
376   /* True if new jumps cannot be created, to replace existing ones or
377      not, at the current point in the compilation.  */
378   bool (* cannot_modify_jumps_p) (void);
379 
380   /* Return a register class for which branch target register
381      optimizations should be applied.  */
382   int (* branch_target_register_class) (void);
383 
384   /* Return true if branch target register optimizations should include
385      callee-saved registers that are not already live during the current
386      function.  AFTER_PE_GEN is true if prologues and epilogues have
387      already been generated.  */
388   bool (* branch_target_register_callee_saved) (bool after_pe_gen);
389 
390   /* True if the constant X cannot be placed in the constant pool.  */
391   bool (* cannot_force_const_mem) (rtx);
392 
393   /* True if the insn X cannot be duplicated.  */
394   bool (* cannot_copy_insn_p) (rtx);
395 
396   /* True if X is considered to be commutative.  */
397   bool (* commutative_p) (rtx, int);
398 
399   /* Given an address RTX, undo the effects of LEGITIMIZE_ADDRESS.  */
400   rtx (* delegitimize_address) (rtx);
401 
402   /* True if it is OK to do sibling call optimization for the specified
403      call expression EXP.  DECL will be the called function, or NULL if
404      this is an indirect call.  */
405   bool (*function_ok_for_sibcall) (tree decl, tree exp);
406 
407   /* True if EXP should be placed in a "small data" section.  */
408   bool (* in_small_data_p) (tree);
409 
410   /* True if EXP names an object for which name resolution must resolve
411      to the current module.  */
412   bool (* binds_local_p) (tree);
413 
414   /* Do something target-specific to record properties of the DECL into
415      the associated SYMBOL_REF.  */
416   void (* encode_section_info) (tree, rtx, int);
417 
418   /* Undo the effects of encode_section_info on the symbol string.  */
419   const char * (* strip_name_encoding) (const char *);
420 
421   /* If shift optabs for MODE are known to always truncate the shift count,
422      return the mask that they apply.  Return 0 otherwise.  */
423   unsigned HOST_WIDE_INT (* shift_truncation_mask) (enum machine_mode mode);
424 
425   /* Return the number of divisions in the given MODE that should be present,
426      so that it is profitable to turn the division into a multiplication by
427      the reciprocal.  */
428   unsigned int (* min_divisions_for_recip_mul) (enum machine_mode mode);
429 
430   /* True if MODE is valid for a pointer in __attribute__((mode("MODE"))).  */
431   bool (* valid_pointer_mode) (enum machine_mode mode);
432 
433   /* True if MODE is valid for the target.  By "valid", we mean able to
434      be manipulated in non-trivial ways.  In particular, this means all
435      the arithmetic is supported.  */
436   bool (* scalar_mode_supported_p) (enum machine_mode mode);
437
438   /* Similarly for vector modes.  "Supported" here is less strict.  At
439      least some operations are supported; need to check optabs or builtins
440      for further details.  */
441   bool (* vector_mode_supported_p) (enum machine_mode mode);
442 
443   /* True if a vector is opaque.  */
444   bool (* vector_opaque_p) (tree);
445 
446   /* Compute a (partial) cost for rtx X.  Return true if the complete
447      cost has been computed, and false if subexpressions should be
448      scanned.  In either case, *TOTAL contains the cost result.  */
449   /* Note that CODE and OUTER_CODE ought to be RTX_CODE, but that's
450      not necessarily defined at this point.  */
451   bool (* rtx_costs) (rtx x, int code, int outer_code, int *total);
452 
453   /* Compute the cost of X, used as an address.  Never called with
454      invalid addresses.  */
455   int (* address_cost) (rtx x);
456 
457   /* Return where to allocate pseudo for a given hard register initial
458      value.  */
459   rtx (* allocate_initial_value) (rtx x);
460 
461   /* Given a register, this hook should return a parallel of registers
462      to represent where to find the register pieces.  Define this hook
463      if the register and its mode are represented in Dwarf in
464      non-contiguous locations, or if the register should be
465      represented in more than one register in Dwarf.  Otherwise, this
466      hook should return NULL_RTX.  */
467   rtx (* dwarf_register_span) (rtx);
468 
469   /* Fetch the fixed register(s) which hold condition codes, for
470      targets where it makes sense to look for duplicate assignments to
471      the condition codes.  This should return true if there is such a
472      register, false otherwise.  The arguments should be set to the
473      fixed register numbers.  Up to two condition code registers are
474      supported.  If there is only one for this target, the int pointed
475      at by the second argument should be set to -1.  */
476   bool (* fixed_condition_code_regs) (unsigned int *, unsigned int *);
477 
478   /* If two condition code modes are compatible, return a condition
479      code mode which is compatible with both, such that a comparison
480      done in the returned mode will work for both of the original
481      modes.  If the condition code modes are not compatible, return
482      VOIDmode.  */
483   enum machine_mode (* cc_modes_compatible) (enum machine_mode,
484                                              enum machine_mode);
485 
486   /* Do machine-dependent code transformations.  Called just before
487      delayed-branch scheduling.  */
488   void (* machine_dependent_reorg) (void);
489 
490   /* Create the __builtin_va_list type.  */
491   tree (* build_builtin_va_list) (void);
492 
493   /* Gimplifies a VA_ARG_EXPR.  */
494   tree (* gimplify_va_arg_expr) (tree valist, tree type, tree *pre_p,
495                                  tree *post_p);
496 
497   /* Validity-checking routines for PCH files, target-specific.
498      get_pch_validity returns a pointer to the data to be stored,
499      and stores the size in its argument.  pch_valid_p gets the same
500      information back and returns NULL if the PCH is valid,
501      or an error message if not.
502   */
503   void * (* get_pch_validity) (size_t *);
504   const char * (* pch_valid_p) (const void *, size_t);
505 
506   /* If nonnull, this function checks whether a PCH file with the
507      given set of target flags can be used.  It returns NULL if so,
508      otherwise it returns an error message.  */
509   const char *(*check_pch_target_flags) (int);
510 
511   /* True if the compiler should give an enum type only as many
512      bytes as it takes to represent the range of possible values of
513      that type.  */
514   bool (* default_short_enums) (void);
515 
516   /* This target hook returns an rtx that is used to store the address
517      of the current frame into the built-in setjmp buffer.  */
518   rtx (* builtin_setjmp_frame_value) (void);
519 
520   /* This target hook should add STRING_CST trees for any hard regs
521      the port wishes to automatically clobber for an asm.  */
522   tree (* md_asm_clobbers) (tree, tree, tree);
523 
524   /* This target hook allows the backend to specify a calling convention
525      in the debug information.  This function actually returns an
526      enum dwarf_calling_convention, but because of forward declarations
527      and not wanting to include dwarf2.h everywhere target.h is included
528      the function is being declared as an int.  */
529   int (* dwarf_calling_convention) (tree);
530 
531   /* This target hook allows the backend to emit frame-related insns that
532      contain UNSPECs or UNSPEC_VOLATILEs.  The call frame debugging info
533      engine will invoke it on insns of the form
534        (set (reg) (unspec [...] UNSPEC_INDEX))
535      and
536        (set (reg) (unspec_volatile [...] UNSPECV_INDEX))
537      to let the backend emit the call frame instructions.  */
538   void (* dwarf_handle_frame_unspec) (const char *, rtx, int);
539 
540   /* Perform architecture specific checking of statements gimplified
541      from VA_ARG_EXPR.  LHS is left hand side of MODIFY_EXPR, RHS
542      is right hand side.  Returns true if the statements doesn't need
543      to be checked for va_list references.  */
544   bool (* stdarg_optimize_hook) (struct stdarg_info *ai, tree lhs, tree rhs);
545 
546   /* This target hook allows the operating system to override the DECL
547      that represents the external variable that contains the stack
548      protection guard variable.  The type of this DECL is ptr_type_node.  */
549   tree (* stack_protect_guard) (void);
550 
551   /* This target hook allows the operating system to override the CALL_EXPR
552      that is invoked when a check vs the guard variable fails.  */
553   tree (* stack_protect_fail) (void);
554 
555   /* Returns NULL if target supports the insn within a doloop block,
556      otherwise it returns an error message.  */
557   const char * (*invalid_within_doloop) (rtx);
558 
559   /* DECL is a variable or function with __attribute__((dllimport))
560      specified.  Use this hook if the target needs to add extra validation
561      checks to  handle_dll_attribute ().  */
562   bool (* valid_dllimport_attribute_p) (tree decl);
563     
564   /* Functions relating to calls - argument passing, returns, etc.  */
565   struct calls {
566     bool (*promote_function_args) (tree fntype);
567     bool (*promote_function_return) (tree fntype);
568     bool (*promote_prototypes) (tree fntype);
569     rtx (*struct_value_rtx) (tree fndecl, int incoming);
570     bool (*return_in_memory) (tree type, tree fndecl);
571     bool (*return_in_msb) (tree type);
572 
573     /* Return true if a parameter must be passed by reference.  TYPE may
574        be null if this is a libcall.  CA may be null if this query is
575        from __builtin_va_arg.  */
576     bool (*pass_by_reference) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
577                                tree type, bool named_arg);
578 
579     rtx (*expand_builtin_saveregs) (void);
580     /* Returns pretend_argument_size.  */
581     void (*setup_incoming_varargs) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
582                                     tree type, int *pretend_arg_size,
583                                     int second_time);
584     bool (*strict_argument_naming) (CUMULATIVE_ARGS *ca);
585     /* Returns true if we should use
586        targetm.calls.setup_incoming_varargs() and/or
587        targetm.calls.strict_argument_naming().  */
588     bool (*pretend_outgoing_varargs_named) (CUMULATIVE_ARGS *ca);
589 
590     /* Given a complex type T, return true if a parameter of type T
591        should be passed as two scalars.  */
592     bool (* split_complex_arg) (tree type);
593 
594     /* Return true if type T, mode MODE, may not be passed in registers,
595        but must be passed on the stack.  */
596     /* ??? This predicate should be applied strictly after pass-by-reference.
597        Need audit to verify that this is the case.  */
598     bool (* must_pass_in_stack) (enum machine_mode mode, tree t);
599 
600     /* Return true if type TYPE, mode MODE, which is passed by reference,
601        should have the object copy generated by the callee rather than
602        the caller.  It is never called for TYPE requiring constructors.  */
603     bool (* callee_copies) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
604                             tree type, bool named);
605 
606     /* Return zero for arguments passed entirely on the stack or entirely
607        in registers.  If passed in both, return the number of bytes passed
608        in registers; the balance is therefore passed on the stack.  */
609     int (* arg_partial_bytes) (CUMULATIVE_ARGS *ca, enum machine_mode mode,
610                                tree type, bool named);
611 
612     /* Return the diagnostic message string if function without a prototype
613        is not allowed for this 'val' argument; NULL otherwise. */
614     const char *(*invalid_arg_for_unprototyped_fn) (tree typelist, 
615                                                     tree funcdecl, tree val);
616 
617     /* Return an rtx for the return value location of the function
618        specified by FN_DECL_OR_TYPE with a return type of RET_TYPE.  */
619     rtx (*function_value) (tree ret_type, tree fn_decl_or_type,
620                            bool outgoing);
621 
622     /* Return an rtx for the argument pointer incoming to the
623        current function.  */
624     rtx (*internal_arg_pointer) (void);
625   } calls;
626 
627   /* Return the diagnostic message string if conversion from FROMTYPE
628      to TOTYPE is not allowed, NULL otherwise.  */
629   const char *(*invalid_conversion) (tree fromtype, tree totype);
630 
631   /* Return the diagnostic message string if the unary operation OP is
632      not permitted on TYPE, NULL otherwise.  */
633   const char *(*invalid_unary_op) (int op, tree type);
634 
635   /* Return the diagnostic message string if the binary operation OP
636      is not permitted on TYPE1 and TYPE2, NULL otherwise.  */
637   const char *(*invalid_binary_op) (int op, tree type1, tree type2);
638 
639   /* Functions specific to the C++ frontend.  */
640   struct cxx {
641     /* Return the integer type used for guard variables.  */
642     tree (*guard_type) (void);
643     /* Return true if only the low bit of the guard should be tested.  */
644     bool (*guard_mask_bit) (void);
645     /* Returns the size of the array cookie for an array of type.  */
646     tree (*get_cookie_size) (tree);
647     /* Returns true if the element size should be stored in the
648        array cookie.  */
649     bool (*cookie_has_size) (void);
650     /* Allows backends to perform additional processing when
651        deciding if a class should be exported or imported.  */
652     int (*import_export_class) (tree, int);
653     /* Returns true if constructors and destructors return "this".  */
654     bool (*cdtor_returns_this) (void);
655     /* Returns true if the key method for a class can be an inline
656        function, so long as it is not declared inline in the class
657        itself.  Returning true is the behavior required by the Itanium
658        C++ ABI.  */
659     bool (*key_method_may_be_inline) (void);
660     /* DECL is a virtual table, virtual table table, typeinfo object,
661        or other similar implicit class data object that will be
662        emitted with external linkage in this translation unit.  No ELF
663        visibility has been explicitly specified.  If the target needs
664        to specify a visibility other than that of the containing class,
665        use this hook to set DECL_VISIBILITY and
666        DECL_VISIBILITY_SPECIFIED.  */ 
667     void (*determine_class_data_visibility) (tree decl);
668     /* Returns true (the default) if virtual tables and other
669        similar implicit class data objects are always COMDAT if they
670        have external linkage.  If this hook returns false, then
671        class data for classes whose virtual table will be emitted in
672        only one translation unit will not be COMDAT.  */
673     bool (*class_data_always_comdat) (void);
674     /* Returns true if __aeabi_atexit should be used to register static
675        destructors.  */
676     bool (*use_aeabi_atexit) (void);
677     /* TYPE is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that
678        has just been defined.  Use this hook to make adjustments to the
679        class  (eg, tweak visibility or perform any other required
680        target modifications).  */  
681     void (*adjust_class_at_definition) (tree type);
682   } cxx;
683 
684   /* True if unwinding tables should be generated by default.  */
685   bool unwind_tables_default;
686 
687   /* Leave the boolean fields at the end.  */
688 
689   /* True if arbitrary sections are supported.  */
690   bool have_named_sections;
691 
692   /* True if "native" constructors and destructors are supported,
693      false if we're using collect2 for the job.  */
694   bool have_ctors_dtors;
695 
696   /* True if thread-local storage is supported.  */
697   bool have_tls;
698 
699   /* True if a small readonly data section is supported.  */
700   bool have_srodata_section;
701 
702   /* True if EH frame info sections should be zero-terminated.  */
703   bool terminate_dw2_eh_frame_info;
704 
705   /* True if #NO_APP should be emitted at the beginning of
706      assembly output.  */
707   bool file_start_app_off;
708 
709   /* True if output_file_directive should be called for main_input_filename
710      at the beginning of assembly output.  */
711   bool file_start_file_directive;
712 
713   /* True if #pragma redefine_extname is to be supported.  */
714   bool handle_pragma_redefine_extname;
715 
716   /* True if #pragma extern_prefix is to be supported.  */
717   bool handle_pragma_extern_prefix;
718 
719   /* True if the target is allowed to reorder memory accesses unless
720      synchronization is explicitly requested.  */
721   bool relaxed_ordering;
722 
723   /* Returns true if we should generate exception tables for use with the
724      ARM EABI.  The effects the encoding of function exception specifications.
725    */
726   bool arm_eabi_unwinder;
727 
728   /* Leave the boolean fields at the end.  */
729 };



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