Re: Patch for Soft-Float Problems w/ Glibc & Gcc?

On Tue, 13 Feb 2001, Mark Hatle wrote:

Grant Erickson wrote:

quoted

For some time I've noted but have never bothered chasing down the *printf
problems associated with using -msoft-float/-D_SOFT_FLOAT on Linux/PPC.

Needing to remedy the issue, I started chasing it down using the code
samples below. When compiled using just '$(CROSS_COMPILE)gcc -o pi-test
*.c' everything works fine:

...

I believe we fixed this problem around CDK 1.2 time.  Unfortunatly I
don't remember what we did to fix the problem.  I am almost sure it has
to do with the spec file for gcc.  (not rpm spec, but the
...lib/gcc-lib/2.95.2/spec.

Give the CDK 1.2 compiler a try on that code and see if it fixes the
problem you are having.  (Keep in mind that you will also need to use
the glibc provided.  The floating point printf fix effects both glibc
and gcc.)

The one patch that makes the difference is the following:

diff -urN gcc-2.95.2.orig/gcc/config/rs6000/linux-nfp.h gcc-2.95.2/gcc/config/rs6000/linux-nfp.h

--- gcc-2.95.2.orig/gcc/config/rs6000/linux-nfp.h       Wed Dec 31 16:00:00 1969
+++ gcc-2.95.2/gcc/config/rs6000/linux-nfp.h    Tue May 30 18:34:05 2000

@@ -0,0 +1,34 @@
+/* Target definitions for GNU compiler for PowerPC running System V.4
+   Copyright (C) 1995, 1996, 1997, 1998, 1999 Free Software Foundation,

Inc.
+   Contributed by Cygnus Support.
+
+Default to soft floating point.
+
+This file is part of GNU CC.
+
+GNU CC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU CC 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU CC; see the file COPYING.  If not, write to
+the Free Software Foundation, 59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA.  */
+
+#include "linux.h"
+
+#undef CPP_SYSV_SPEC
+#define CPP_SYSV_SPEC \
+"%{mrelocatable*: -D_RELOCATABLE} \
+%{fpic: -D__PIC__=1 -D__pic__=1} \
+%{!fpic: %{fPIC: -D__PIC__=2 -D__pic__=2}} \
+%{mcall-sysv: -D_CALL_SYSV} %{mcall-nt: -D_CALL_NT} \
+%{mcall-aix: -D_CALL_AIX} %{mcall-aixdesc: -D_CALL_AIX -D_CALL_AIXDESC} \
+%{!mcall-sysv: %{!mcall-aix: %{!mcall-aixdesc: %{!mcall-nt: %(cpp_sysv_default) }}}} \
+%{!mhard-float: -D_SOFT_FLOAT} %{mcpu=403: -D_SOFT_FLOAT}"
diff -urN gcc-2.95.2.orig/gcc/configure gcc-2.95.2/gcc/configure

--- gcc-2.95.2.orig/gcc/configure       Wed Oct 13 00:58:02 1999
+++ gcc-2.95.2/gcc/configure    Tue May 30 18:27:12 2000

@@ -5127,7 +5127,12 @@
                fi
                ;;
        powerpc-*-linux-gnu*)
-               tm_file=rs6000/linux.h
+               if test x$with_fp = xno
+               then
+                       tm_file=rs6000/linux-nfp.h
+               else
+                       tm_file=rs6000/linux.h
+               fi
                xm_file="xm-siglist.h rs6000/xm-sysv4.h"
                xm_defines="USG ${xm_defines}"
                out_file=rs6000/rs6000.c

This is included with all of the other non-FPU patches typically applied
for the 4xx or 8xx processors. The one single difference that this has is
on the spec file produced for gcc. What was:

*cpp_sysv:
[ ... some stuff ... ] {msoft-float: -D_SOFT_FLOAT} [ ... more stuff ... ]

changes to:

*cpp_sysv:
[ ... some stuff ... ] {!mhard-float: -D_SOFT_FLOAT} [ ... more stuff ... ]

After regenerating gcc 2.95.3-test3 and glibc 2.1.3, the results are
promising:

	grant@stcroix% ./pi-test-hard
	The value of Pi is approximately: 3.142857

	grant@stcroix% ./pi-test-soft
	The value of Pi is approximately: 3.142857

Thanks a lot to those who offered suggestions over the course of the day!

Best regards,

Grant Erickson


--
 Grant Erickson                       University of Minnesota Alumni
  o mail:erick205@umn.edu                                 1996 BSEE
  o http://www.umn.edu/~erick205                          1998 MSEE


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