diff options
Diffstat (limited to 'sysdeps/m68k/fpu/switch/switch.c')
| -rw-r--r-- | sysdeps/m68k/fpu/switch/switch.c | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/sysdeps/m68k/fpu/switch/switch.c b/sysdeps/m68k/fpu/switch/switch.c new file mode 100644 index 0000000000..e0558176dc --- /dev/null +++ b/sysdeps/m68k/fpu/switch/switch.c @@ -0,0 +1,87 @@ +/* Copyright (C) 1991, 1992, 1997 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library 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 + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <signal.h> +#include <68881-sw.h> + + +/* The signal that is sent when a 68881 instruction + is executed and there is no 68881. */ +#ifndef TRAPSIG +#define TRAPSIG SIGILL +#endif + +/* Zero if no 68881, one if we have a 68881, or -1 if we don't know yet. */ +static int have_fpu = -1; + + +/* Signal handler for the trap that happens if we don't have a 68881. */ +static void +trap (sig) + int sig; +{ + have_fpu = 0; +} + +/* This function is called by functions that want to switch. + The calling function must be a `struct switch_caller' in data space. + It determines whether a 68881 is present, and modifies its caller + to be a static jump to either the 68881 version or the soft version. + It then returns into the function it has chosen to do the work. */ +void +__68881_switch (dummy) + int dummy; +{ + void **return_address_location = &((void **) &dummy)[-1]; + struct switch_caller *const caller + = (struct switch_caller *) (((short int *) *return_address_location) - 1); + + if (have_fpu < 0) + { + /* Figure out whether or not we have a 68881. */ + __sighandler_t handler = signal (TRAPSIG, trap); + if (handler == SIG_ERR) + /* We can't figure it out, so assume we don't have a 68881. + This assumption will never cause us any problems other than + lost performance, while the reverse assumption could cause + the program to crash. */ + have_fpu = 0; + else + { + /* We set `have_fpu' to nonzero, and then execute a 68881 + no-op instruction. If we have a 68881, this will do nothing. + If we don't have one, this will trap and the signal handler + will clear `have_fpu'. */ + have_fpu = 1; + asm ("fnop"); + + /* Restore the old signal handler. */ + (void) signal (TRAPSIG, handler); + } + } + + /* Modify the caller to be a jump to the appropriate address. */ + caller->insn = JMP; + caller->target = have_fpu ? caller->fpu : caller->soft; + + /* Make the address we will return to be the target we have chosen. + Our return will match the `jsr' done by the caller we have + just modified, and it will be just as if that had instead + been a `jmp' to the new target. */ + *return_address_location = caller->target; +} |