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Re:   problem while building arm vfp softfloat gcc 


Nicolas Pitre wrote:
On 10 Feb 2004, add wrote:

I have already tried this on my platform, it still print out 0.000000
so it seems like a problem of glibc.
I swapped the register according to montavista's iwmmxt_le-gcc produced asm
code. Are you sure that code is correct? if so, then that means montavista's
toolchain is not compatible with others, although it uses the same vfp
softfloat patch.

*** Beware ***


MV's iwmmxt_le toolchain is using VFP word ordering. My soft-float patch is also using VFP word ordering by default.

*** However ***

Libraries like glibc need to be aware of it too, since they play with doubl float values directly. See for example this patch I produced for uClibc: ...

Attached is a patch from addsub@eyou.com that he says patches glibc and makes printf("%f", 1.0) work again. I haven't tested it, just wanted to give Nico a chance to have a look at it. Not sure if addsub wrote this himself or whether it's suitable for glibc mainline (I've asked him). - Dan


-- US citizens: if you're considering voting for Bush, look at these first: http://www.misleader.org/ http://www.cbc.ca/news/background/arar/ http://www.house.gov/reform/min/politicsandscience/
diff -uNrp glibc.old/sysdeps/arm/bits/endian.h glibc.new/sysdeps/arm/bits/endian.h
--- glibc.old/sysdeps/arm/bits/endian.h	1999-04-12 11:59:13.000000000 -0400
+++ glibc.new/sysdeps/arm/bits/endian.h	2004-02-12 09:15:13.000000000 -0500
@@ -9,4 +9,9 @@
 #else
 #define __BYTE_ORDER __LITTLE_ENDIAN
 #endif
+
+#ifdef __VFP_FP__
+#define __FLOAT_WORD_ORDER __BYTE_ORDER
+#else
 #define __FLOAT_WORD_ORDER __BIG_ENDIAN
+#endif
diff -uNrp glibc.old/sysdeps/arm/gmp-mparam.h glibc.new/sysdeps/arm/gmp-mparam.h
--- glibc.old/sysdeps/arm/gmp-mparam.h	2001-07-07 15:21:19.000000000 -0400
+++ glibc.new/sysdeps/arm/gmp-mparam.h	2004-02-12 09:15:13.000000000 -0500
@@ -26,5 +26,13 @@ MA 02111-1307, USA. */
 #define BITS_PER_SHORTINT 16
 #define BITS_PER_CHAR 8
 
-#define IEEE_DOUBLE_BIG_ENDIAN 0
-#define IEEE_DOUBLE_MIXED_ENDIAN 1
+#if defined(__ARMEB__)
+# define IEEE_DOUBLE_MIXED_ENDIAN 0
+# define IEEE_DOUBLE_BIG_ENDIAN 1
+#elif defined(__VFP_FP__)
+# define IEEE_DOUBLE_MIXED_ENDIAN 0
+# define IEEE_DOUBLE_BIG_ENDIAN 0
+#else
+# define IEEE_DOUBLE_BIG_ENDIAN 0
+# define IEEE_DOUBLE_MIXED_ENDIAN 1
+#endif
diff -uNrp glibc.old/sysdeps/arm/ieee754.h glibc.new/sysdeps/arm/ieee754.h
--- glibc.old/sysdeps/arm/ieee754.h	2001-07-07 15:21:19.000000000 -0400
+++ glibc.new/sysdeps/arm/ieee754.h	1969-12-31 19:00:00.000000000 -0500
@@ -1,115 +0,0 @@
-/* Copyright (C) 1992, 1995, 1996, 1998 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.  */
-
-#ifndef _IEEE754_H
-
-#define _IEEE754_H 1
-#include <features.h>
-
-#include <endian.h>
-
-__BEGIN_DECLS
-
-union ieee754_float
-  {
-    float f;
-
-    /* This is the IEEE 754 single-precision format.  */
-    struct
-      {
-	unsigned int mantissa:23;
-	unsigned int exponent:8;
-	unsigned int negative:1;
-      } ieee;
-
-    /* This format makes it easier to see if a NaN is a signalling NaN.  */
-    struct
-      {
-	unsigned int mantissa:22;
-	unsigned int quiet_nan:1;
-	unsigned int exponent:8;
-	unsigned int negative:1;
-      } ieee_nan;
-  };
-
-#define IEEE754_FLOAT_BIAS	0x7f /* Added to exponent.  */
-
-
-union ieee754_double
-  {
-    double d;
-
-    /* This is the IEEE 754 double-precision format.  */
-    struct
-      {
-	unsigned int mantissa0:20;
-	unsigned int exponent:11;
-	unsigned int negative:1;
-	unsigned int mantissa1:32;
-      } ieee;
-
-    /* This format makes it easier to see if a NaN is a signalling NaN.  */
-    struct
-      {
-	unsigned int mantissa0:19;
-	unsigned int quiet_nan:1;
-	unsigned int exponent:11;
-	unsigned int negative:1;
-	unsigned int mantissa1:32;
-      } ieee_nan;
-  };
-
-#define IEEE754_DOUBLE_BIAS	0x3ff /* Added to exponent.  */
-
-
-/* The following two structures are correct for `new' floating point systems but
-   wrong for the old FPPC.  The only solution seems to be to avoid their use on
-   old hardware.  */
-
-union ieee854_long_double
-  {
-    long double d;
-
-    /* This is the IEEE 854 double-extended-precision format.  */
-    struct
-      {
-	unsigned int exponent:15;
-	unsigned int empty:16;
-	unsigned int negative:1;
-	unsigned int mantissa1:32;
-	unsigned int mantissa0:32;
-      } ieee;
-
-    /* This is for NaNs in the IEEE 854 double-extended-precision format.  */
-    struct
-      {
-	unsigned int exponent:15;
-	unsigned int empty:16;
-	unsigned int negative:1;
-	unsigned int mantissa1:32;
-	unsigned int mantissa0:30;
-	unsigned int quiet_nan:1;
-	unsigned int one:1;
-      } ieee_nan;
-  };
-
-#define IEEE854_LONG_DOUBLE_BIAS 0x3fff
-
-__END_DECLS
-
-#endif /* ieee754.h */

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