Re: need help in 64-bit code

[Mike DeKoker <mdekoker@xxxxxxxxx>]

--- sudheer <urwithsudheer@xxxxxxxxx> wrote:

> Hi Thomas,
> 
> Thomas Petazzoni wrote:
> 
> >Hi,
> >
> >Le Fri, 05 May 2006 18:02:48 +0530,
> >sudheer <urwithsudheer@xxxxxxxxx> a écrit :
> >
> >  
> >
> >>To have  the compatability i have used  the macro
> CONFIG_X86_64 in 
> >>.config  .
> >>    
> >>
> >
> >Why do you need to differentiate code executed on
> 32 bits platforms
> >from code executed on 64 bits platform ? Generally
> speaking, your code
> >should be portable, and not rely on CONFIG_X86_64
> or other options of
> >the same kind.
> >
> >  
> >
> I want to assign some data to a long pointer
> variable SysAdddr.
> 
> #ifdef CONFIG_64
> *(SysAddr + num_items) = (0xaa55aa55aa000000 +
> num_items);
> #else
> *(SysAddr + num_items) = (0x11220000 + (num_items));
> #endif
> If it is 64 but system i should assign 64 bit or
> else 32 bit data.
> Can i have any other option/method ?
> 
> Thanks
> Sudheer
> 
> 
> 

As previously mentioned your code should be portable
and not rely on architecture specific things like
pointer size. That being said, here's another way to
do this at roughly compile time:

if (sizeof(long) > 4)
{
 *(SysAddr + num_items) = 
   (0xaa55aa55aa000000 + num_items);
}
else
{
 *(SysAddr + num_items) = 
   (0x11220000 + (num_items));
}

The optimizer should remove the extraneous branch of
code.

Mike DeKoker
Signatec, Inc.

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