RE: [PATCH CR16] Added some missing instructions

[Sandeep Kumar Singh <Sandeep dot Singh2 at kpitcummins dot com>]

Hi Corinna,

>> Can you please explain the background why instructions, which were 
>> supposedly available since 2010 are suddenly "unsupported"?

CR16 port of Newlib was developed with taking references from existing CRX 
port. These two National semiconductor targets have many architectural 
similarities, among them include very similar instruction set.

I am sure because of this, when asm.h was included in the initial Newlib port
of CR16 it was taken as is from CRX port. However, recently we found some of 
the instructions supported by CR16, were missing in this file viz. lpr, lprd, 
spr, sprd.

While adding these instructions in asm.h, we also found it has few other CRX 
instructions which are not supported by CR16. Hence in the same patch, we are
removing these unsupported instructions.

>> Wouldn't that potentially break existing code?

I believe it should not break existing code, as these instructions are not 
supported by the CR16 architecture.

Thanks and Regards,
Sandeep Kumar Singh,
KPIT Cummins InfoSystems Ltd.
Pune, India


-----Original Message-----
From: Corinna Vinschen [mailto:vinschen@redhat.com] 
Sent: Thursday, May 03, 2012 8:48 PM
To: Sandeep Kumar Singh
Cc: newlib@sourceware.org; Jayant R. Sonar; Kaushik Phatak
Subject: Re: [PATCH CR16] Added some missing instructions

Hi Sandeep,

On May  3 09:52, Sandeep Kumar Singh wrote:
> Hi,
> 
> Please find the attached patch "cr16-newlib.patch" for cr16 target. It adds
> some missing instructions, removes few un-supported ones and fixes constraints
> of few other instructions.
> 
> Please review the patch and let me know if there should be any modifications 
> in it.
> 
> newlib/ChangeLog
> 
> 2012-05-03  Sandeep Kumar Singh  <Sandeep.Singh2@kpitcummins.com>
> 
> 	* libc/machine/cr16/asm.h: Added some missing instructions 
> 	and removed few unsupported instructions of cr16 target.

I'm a bit puzzled.  You're removing instructions from this file, which
were available since 2010.  I'm not sure this is feasible.  Wouldn't
that potentially break existing code?

Can you please explain the background why instructions, which were
supposedly available since 2010 are suddenly "unsupported"?


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Project Co-Leader
Red Hat