gcc/target.h

/* Data structure definitions for a generic GCC target.
   Copyright (C) 2001, 2002 Free Software Foundation, Inc.

This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

 In other words, you are welcome to use, share and improve this program.
 You are forbidden to forbid anyone else to use, share and improve
 what you give them.   Help stamp out software-hoarding!  */

/* This file contains a data structure that describes a GCC target.
   At present it is incomplete, but in future it should grow to
   contain most or all target machine and target O/S specific
   information.

   This structure has its initializer declared in target-def.h in the
   form of large macro TARGET_INITIALIZER that expands to many smaller
   macros.

   The smaller macros each initialize one component of the structure,
   and each has a default.  Each target should have a file that
   includes target.h and target-def.h, and overrides any inappropriate
   defaults by undefining the relevant macro and defining a suitable
   replacement.  That file should then contain the definition of
   "targetm" like so:

   struct gcc_target targetm = TARGET_INITIALIZER;

   Doing things this way allows us to bring together everything that
   defines a GCC target.  By supplying a default that is appropriate
   to most targets, we can easily add new items without needing to
   edit dozens of target configuration files.  It should also allow us
   to gradually reduce the amount of conditional compilation that is
   scattered throughout GCC.  */

struct gcc_target
{
  /* Functions that output assembler for the target.  */
  struct asm_out
  {
    /* Opening and closing parentheses for asm expression grouping.  */
    const char *open_paren, *close_paren;

    /* Assembler instructions for creating various kinds of integer object.  */
    const char *byte_op;
    struct asm_int_op
    {
      const char *hi;
      const char *si;
      const char *di;
      const char *ti;
    } aligned_op, unaligned_op;

    /* Try to output the assembler code for an integer object whose
       value is given by X.  SIZE is the size of the object in bytes and
       ALIGNED_P indicates whether it is aligned.  Return true if
       successful.  Only handles cases for which BYTE_OP, ALIGNED_OP
       and UNALIGNED_OP are NULL.  */
    bool (* integer) PARAMS ((rtx x, unsigned int size, int aligned_p));

    /* Output the assembler code for entry to a function.  */
    void (* function_prologue) PARAMS ((FILE *, HOST_WIDE_INT));

    /* Output the assembler code for end of prologue.  */
    void (* function_end_prologue) PARAMS ((FILE *));

    /* Output the assembler code for start of epilogue.  */
    void (* function_begin_epilogue) PARAMS ((FILE *));

    /* Output the assembler code for function exit.  */
    void (* function_epilogue) PARAMS ((FILE *, HOST_WIDE_INT));

    /* Switch to an arbitrary section NAME with attributes as
       specified by FLAGS.  */
    void (* named_section) PARAMS ((const char *, unsigned int));

    /* Switch to the section that holds the exception table.  */
    void (* exception_section) PARAMS ((void));

    /* Switch to the section that holds the exception frames.  */
    void (* eh_frame_section) PARAMS ((void));

    /* Output a constructor for a symbol with a given priority.  */
    void (* constructor) PARAMS ((rtx, int));

    /* Output a destructor for a symbol with a given priority.  */
    void (* destructor) PARAMS ((rtx, int));
  } asm_out;

  /* Functions relating to instruction scheduling.  */
  struct sched
  {
    /* Given the current cost, COST, of an insn, INSN, calculate and
       return a new cost based on its relationship to DEP_INSN through
       the dependence LINK.  The default is to make no adjustment.  */
    int (* adjust_cost) PARAMS ((rtx insn, rtx link, rtx def_insn, int cost));

    /* Adjust the priority of an insn as you see fit.  Returns the new
       priority.  */
    int (* adjust_priority) PARAMS ((rtx, int));

    /* Function which returns the maximum number of insns that can be
       scheduled in the same machine cycle.  This must be constant
       over an entire compilation.  The default is 1.  */
    int (* issue_rate) PARAMS ((void));

    /* Calculate how much this insn affects how many more insns we
       can emit this cycle.  Default is they all cost the same.  */
    int (* variable_issue) PARAMS ((FILE *, int, rtx, int));
    
    /* Initialize machine-dependent scheduling code.  */
    void (* md_init) PARAMS ((FILE *, int, int));

    /* Finalize machine-dependent scheduling code.  */
    void (* md_finish) PARAMS ((FILE *, int));

    /* Reorder insns in a machine-dependent fashion, in two different
       places.  Default does nothing.  */
    int (* reorder)  PARAMS ((FILE *, int, rtx *, int *, int));
    int (* reorder2) PARAMS ((FILE *, int, rtx *, int *, int));

    /* cycle_display is a pointer to a function which can emit
       data into the assembly stream about the current cycle.
       Arguments are CLOCK, the data to emit, and LAST, the last
       insn in the new chain we're building.  Returns a new LAST.
       The default is to do nothing.  */
    rtx (* cycle_display) PARAMS ((int clock, rtx last));
  } sched;

  /* Given two decls, merge their attributes and return the result.  */
  tree (* merge_decl_attributes) PARAMS ((tree, tree));

  /* Given two types, merge their attributes and return the result.  */
  tree (* merge_type_attributes) PARAMS ((tree, tree));

  /* Table of machine attributes and functions to handle them.  */
  const struct attribute_spec *attribute_table;

  /* Return zero if the attributes on TYPE1 and TYPE2 are incompatible,
     one if they are compatible and two if they are nearly compatible
     (which causes a warning to be generated).  */
  int (* comp_type_attributes) PARAMS ((tree type1, tree type2));

  /* Assign default attributes to the newly defined TYPE.  */
  void (* set_default_type_attributes) PARAMS ((tree type));

  /* Insert attributes on the newly created DECL.  */
  void (* insert_attributes) PARAMS ((tree decl, tree *attributes));

  /* Return true if FNDECL (which has at least one machine attribute)
     can be inlined despite its machine attributes, false otherwise.  */
  bool (* function_attribute_inlinable_p) PARAMS ((tree fndecl));

  /* Return true if bitfields in RECORD_TYPE should follow the
     Microsoft Visual C++ bitfield layout rules.  */
  bool (* ms_bitfield_layout_p) PARAMS ((tree record_type));

  /* Set up target-specific built-in functions.  */
  void (* init_builtins) PARAMS ((void));

  /* Expand a target-specific builtin.  */
  rtx (* expand_builtin) PARAMS ((tree exp, rtx target, rtx subtarget,
				  enum machine_mode mode, int ignore));

  /* Given a decl, a section name, and whether the decl initializer
     has relocs, choose attributes for the section.  */
  /* ??? Should be merged with SELECT_SECTION and UNIQUE_SECTION.  */
  unsigned int (* section_type_flags) PARAMS ((tree, const char *, int));

  /* True if arbitrary sections are supported.  */
  bool have_named_sections;

  /* True if "native" constructors and destructors are supported,
     false if we're using collect2 for the job.  */
  bool have_ctors_dtors;

  /* True if new jumps cannot be created, to replace existing ones or
     not, at the current point in the compilation.  */
  bool (* cannot_modify_jumps_p) PARAMS ((void));
};

extern struct gcc_target targetm;