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Re: [RESUME] fpu emulator

To: Andreas Jaeger <aj@suse.de>
Subject: Re: [RESUME] fpu emulator
From: Jun Sun <jsun@mvista.com>
Date: Fri, 09 Feb 2001 11:30:57 -0800
Cc: "Kevin D. Kissell" <kevink@mips.com>, Florian Lohoff <flo@rfc822.org>, linux-mips@oss.sgi.com
References: <20010208122030.A5408@paradigm.rfc822.org> <005d01c091c4$69940620$0deca8c0@Ulysses> <hor919tm4a.fsf@gee.suse.de> <3A8304C0.D3CFFEF7@mvista.com> <hoae7wjjvy.fsf@gee.suse.de>
Sender: owner-linux-mips@oss.sgi.com
Andreas Jaeger wrote:
> 
> Jun Sun <jsun@mvista.com> writes:
> 
> > Andreas Jaeger wrote:
> > >
> >
> > > > saves/restores the FP registers in setjmp/longjmp, the
> > >
> > > Any ideas how this can be done?
> > >
> > > > model of "simply sending SIGILL/SIGFPE" will result
> > > > in *all* processes being terminated with extreme prejudice,
> > > > starting with init!
> > >
> >
> > There is a patch for glibc2.0.7, which I think was done by Jay Carlson.  It
> > basically works for glibc2.0.6 as well.  See the one for glibc2.0.6 attached
> > below.
> >
> > I think the patch is not "clean", in the sense that you only want to apply 
> > it
> > if you want to configure with "--without-fp".  Otherwise the patch will 
> > break
> > other configurations.
> >
> > Jun--- glibc-2.0.6/sysdeps/mips/__longjmp.c.orig-rpm  Sat Sep 11 00:01:44 
> > 1999
> > +++ glibc-2.0.6/sysdeps/mips/__longjmp.c      Sat Sep 11 00:02:36 1999
> > @@ -35,6 +35,7 @@
> >       along the way.  */
> >    register int val asm ("a1");
> >
> > +#ifdef __HAVE_FPU__
> 
> I looked through the whole of glibc and GCC and __HAVE_FPU__ is nowhere
> defined for MIPS.  __HAVE_FPU__ is defined for m68k in GCC but that's
> the only platform.
>

You are right - it is not defined in glibc.  Instead it is defined in egcs. 
For this particular build, I need to apply the mips patch for egcs 1.0.3a,
which supplies __HAVE_FPU__.  You can find it somewhere on oss.sgi site. 
There is an additional patch for softfloat which makes __HAVE_FPU__
conditional.  See the attachement.
 
> Therefore I don't think the patch makes any sense at all,

Therefore, it does make sense. :-)

Jun
--- egcs-1.0.3a/gcc/config/mips/t-linux.orig    Mon Sep  6 21:38:16 1999
+++ egcs-1.0.3a/gcc/config/mips/t-linux Wed Sep  8 08:43:58 1999
@@ -9,8 +9,28 @@
 LIBGCC1 =
 CROSS_LIBGCC1 =
 
-MULTILIB_OPTIONS= EL/EB
-MULTILIB_DIRNAMES= el eb
+# These are really part of libgcc1, but this will cause them to be
+# built correctly, so... [taken from t-sparclite]
+LIB2FUNCS_EXTRA = fp-bit.c dp-bit.c
+
+dp-bit.c: $(srcdir)/config/fp-bit.c
+       echo '#ifdef __MIPSEL__' > dp-bit.c
+       echo '#define FLOAT_BIT_ORDER_MISMATCH' >> dp-bit.c
+       echo '#endif' >> dp-bit.c
+       echo '#define US_SOFTWARE_GOFAST' >> dp-bit.c
+       cat $(srcdir)/config/fp-bit.c >> dp-bit.c
+
+fp-bit.c: $(srcdir)/config/fp-bit.c
+       echo '#define FLOAT' > fp-bit.c
+       echo '#ifdef __MIPSEL__' >> fp-bit.c
+       echo '#define FLOAT_BIT_ORDER_MISMATCH' >> fp-bit.c
+       echo '#endif' >> fp-bit.c
+       echo '#define US_SOFTWARE_GOFAST' >> fp-bit.c
+       cat $(srcdir)/config/fp-bit.c >> fp-bit.c
+
+
+MULTILIB_OPTIONS= EL/EB msoft-float
+MULTILIB_DIRNAMES= el eb soft-float
 MULTILIB_MATCHES=
 MULTILIB_EXCEPTIONS=
 
--- egcs-1.0.3a/gcc/config/mips/linux.h.orig    Mon Sep  6 21:38:16 1999
+++ egcs-1.0.3a/gcc/config/mips/linux.h Wed Sep  8 08:43:40 1999
@@ -82,7 +82,7 @@
 %{!mabi*: -U__mips64} \
 %{fno-PIC:-U__PIC__ -U__pic__} %{fno-pic:-U__PIC__ -U__pic__} \
 %{fPIC:-D__PIC__ -D__pic__} %{fpic:-D__PIC__ -D__pic__} \
-%{-D__HAVE_FPU__ } \
+%{!msoft-float: -D__HAVE_FPU__ } \
 %{posix:-D_POSIX_SOURCE} \
 %{pthread:-D_REENTRANT}"
 
@@ -756,3 +756,7 @@
 
 #undef MAX_WCHAR_TYPE_SIZE
 #define MAX_WCHAR_TYPE_SIZE    MAX_LONG_TYPE_SIZE
+
+/* US Software GOFAST library support.  */
+#include "gofast.h"
+#define INIT_TARGET_OPTABS INIT_GOFAST_OPTABS
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