[RFA] ARM IEEE byte ordering patch

[J. Johnston]

Nick Clifton wrote:
> 
> Hi Jeff,
> 
>   Intel recently turned up a bug in newlib with this simple test
>   program:
> 
>       int
>       main (void)
>       {
>         return printf ("%f\n", 1000000000000000.0);
>       }
> 
>   Which for little endian ARMs will print rubbish.  It turns out that
>   this is because of ARMs weird IEEE format where the words are always
>   stored in big endian order, even though the bytes inside the words
>   are stored in the target's native format.  It was thought that this
>   made no difference to newlib, but it turns out that there is one
>   macro - Storeinc - which is affected.
> 
>   The patch below fixes this problem, by defining
>   __IEEE_BYTES_LITTLE_ENDIAN for little endian ARMs and then selecting
>   the correct definition of Storeinc based partially on this
>   definition.
> 
>   May I apply the patch ?
> 

Please do.

-- Jeff J.

> Cheers
> 
> Nick
> 
> 2001-06-27  Nick Clifton  <nickc@cambridge.redhat.com>
> 
>         * libc/include/machine/ieeefp.h (__IEEE_BYTES_LITTLE_ENDIAN):
>         Define for little endian ARMs.
> 
>         * libc/stdlib/mprec.h (Storeinc): Use little endian version if
>         __IEEE_BYTES_LITTLE_ENDIAN is defined.
> 
> Index: include/machine/ieeefp.h
> ===================================================================
> RCS file: /cvs/src/src/newlib/libc/include/machine/ieeefp.h,v
> retrieving revision 1.5
> diff -p -r1.5 ieeefp.h
> *** ieeefp.h    2001/04/04 13:30:58     1.5
> --- ieeefp.h    2001/06/27 08:57:19
> ***************
> *** 21,29 ****
> 
>   #if defined(__arm__) || defined(__thumb__)
>   /* ARM always has big-endian words.  Within those words the byte ordering
> !    appears to be big or little endian.  Newlib doesn't seem to care about
> !    the byte ordering within words.  */
>   #define __IEEE_BIG_ENDIAN
>   #endif
> 
>   #ifdef __hppa__
> --- 21,31 ----
> 
>   #if defined(__arm__) || defined(__thumb__)
>   /* ARM always has big-endian words.  Within those words the byte ordering
> !    will be big or little endian depending upon the target.  */
>   #define __IEEE_BIG_ENDIAN
> + #ifdef __ARMEL__
> + #define __IEEE_BYTES_LITTLE_ENDIAN
> + #endif
>   #endif
> 
>   #ifdef __hppa__
> Index: stdlib/mprec.h
> ===================================================================
> RCS file: /cvs/src/src/newlib/libc/stdlib/mprec.h,v
> retrieving revision 1.1.1.1
> diff -p -r1.1.1.1 mprec.h
> *** mprec.h     2000/02/17 19:39:48     1.1.1.1
> --- mprec.h     2001/06/27 08:57:20
> *************** union double_union
> *** 81,87 ****
>    * An alternative that might be better on some machines is
>    * #define Storeinc(a,b,c) (*a++ = b << 16 | c & 0xffff)
>    */
> ! #if defined(IEEE_8087) + defined(VAX)
>   #define Storeinc(a,b,c) (((unsigned short *)a)[1] = (unsigned short)b, \
>   ((unsigned short *)a)[0] = (unsigned short)c, a++)
>   #else
> --- 81,87 ----
>    * An alternative that might be better on some machines is
>    * #define Storeinc(a,b,c) (*a++ = b << 16 | c & 0xffff)
>    */
> ! #if defined (__IEEE_BYTES_LITTLE_ENDIAN) + defined (IEEE_8087) + defined (VAX)
>   #define Storeinc(a,b,c) (((unsigned short *)a)[1] = (unsigned short)b, \
>   ((unsigned short *)a)[0] = (unsigned short)c, a++)
>   #else