Guarantee valid sp_register and Free _prior_ to execution of ffree

instruction which might raise SIGFPE.  This ensures that the trap
handler gets the right values for recovery.

diff --git a/v7/src/microcode/cmpauxmd/i386.m4 b/v7/src/microcode/cmpauxmd/i386.m4
index 3f592ccdefaa33b335246f4810609bf30fbe8ca5..dcfd3c1af6948c82ad01402e8f85276309ac76d7 100644 (file)
--- a/v7/src/microcode/cmpauxmd/i386.m4
+++ b/v7/src/microcode/cmpauxmd/i386.m4
@@ -1,9 +1,9 @@
 ### -*-Midas-*-
 ###
-### $Id: i386.m4,v 1.63 2003/10/31 20:45:35 cph Exp $
+### $Id: i386.m4,v 1.64 2005/06/26 04:31:47 cph Exp $
 ###
 ### Copyright 1992,1997,1998,2000,2001 Massachusetts Institute of Technology
-### Copyright 2002,2003 Massachusetts Institute of Technology
+### Copyright 2002,2003,2005 Massachusetts Institute of Technology
 ###
 ### This file is part of MIT/GNU Scheme.
 ###
@@ -538,6 +538,12 @@ define_debugging_label(scheme_to_interface_call)
 \f
 define_hook_label(scheme_to_interface)
 define_debugging_label(scheme_to_interface)
+
+# These two moves must happen _before_ the ffree instructions below.
+# Otherwise recovery from SIGFPE there will fail.
+       OP(mov,l)       TW(REG(esp),EVR(sp_register))
+       OP(mov,l)       TW(rfree,EVR(Free))
+
 IF387(`
        OP(cmp,l)       TW(IMM(0),ABS(EVR(i387_presence)))
        je      scheme_to_interface_proceed
@@ -551,8 +557,6 @@ IF387(`
        ffree   ST(7)
 scheme_to_interface_proceed:
 ')
-       OP(mov,l)       TW(REG(esp),EVR(sp_register))
-       OP(mov,l)       TW(rfree,EVR(Free))
 
        OP(mov,l)       TW(EVR(C_Stack_Pointer),REG(esp))
        OP(mov,l)       TW(EVR(C_Frame_Pointer),REG(ebp))