88 lines
3.0 KiB
C
88 lines
3.0 KiB
C
/* 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;
|
|
}
|