1 files changed, 86 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..057bd1509a
--- /dev/null
+++ b/sysdeps/m68k/fpu/switch/switch.c
@@ -0,0 +1,86 @@
+/* Copyright (C) 1991, 1992 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 Library General Public License as
+published by the Free Software Foundation; either version 2 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
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB.  If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA.  */
+
+#include <ansidecl.h>
+#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
+DEFUN(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
+DEFUN(__68881_switch, (dummy), int dummy)
+{
+  PTR *return_address_location = &((PTR *) &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;
+}