sysdeps/m68k/fpu/switch/68881-sw.h

   1 /* Copyright (C) 1991, 1992, 1997, 2000 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library 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 GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #ifndef _68881_SWITCH_H
  20
  21 #define _68881_SWITCH_H 1
  22 #include <sys/cdefs.h>
  23
  24 /* This is the format of the data at the code label for a function which
  25    wants to switch depending on whether or not a 68881 is present.
  26
  27    Initially, `insn' is a `jsr' instruction, and `target' is __68881_switch.
  28    The first time such a function is called, __68881_switch determines whether
  29    or not a 68881 is present, and modifies the function accordingly.
  30    Then `insn' is a `jmp' instruction, and `target' is the value of `fpu'
  31    if there is 68881, or the value of `soft' if not.  */
  32
  33 struct switch_caller
  34   {
  35     unsigned short int insn;    /* The `jsr' or `jmp' instruction.  */
  36     void *target;               /* The target of the instruction.  */
  37     void *soft;                 /* The address of the soft function.  */
  38     void *fpu;                  /* The address of the 68881 function.  */
  39   };
  40
  41 /* These are opcodes (values for `insn', above) for `jmp' and `jsr'
  42    instructions, respectively, to 32-bit absolute addresses.  */
  43 #define JMP     0x4ef9
  44 #define JSR     0x4eb9
  45
  46
  47 /* Function to determine whether or not a 68881 is available,
  48    and modify its caller (which must be a `struct switch_caller', above,
  49    in data space) to use the appropriate version.  */
  50 extern void __68881_switch (int __dummy) __THROW;
  51
  52
  53 /* Define FUNCTION as a `struct switch_caller' which will call
  54    `__FUNCTION_68881' if a 68881 is present, and `__FUNCTION_soft' if not.
  55 #define switching_function(FUNCTION)                                          \
  56   struct switch_caller FUNCTION =                                             \
  57     {                                                                         \
  58       JSR, (__ptr_t) __68881_switch,                                          \
  59       __CONCAT(__CONCAT(__,FUNCTION),_soft),                                  \
  60       __CONCAT(__CONCAT(__,FUNCTION),_68881)                                  \
  61     }
  62
  63
  64 #endif  /* 68881-switch.h  */