[PATCH] S/390: HW accelerated iconv module for iso-8859-1/cp37 conversions

[Florian Weimer]

On 10/13/2015 01:50 PM, Andreas Krebbel wrote:
> On 10/13/2015 12:40 PM, Andreas Schwab wrote:
>> "Andreas Krebbel" <krebbel@linux.vnet.ibm.com> writes:
>>
>>> +    asm volatile ("0:                        \n\t"			\
>>> +                  "  troo    %0,%1           \n\t"			\
>>> +                  "  jz      1f              \n\t"			\
>>> +                  "  jo      0b              \n\t"			\
>>> +                  "  llgc    %3,0(%1)        \n\t"			\
>>> +                  "  la      %3,0(%3,%4)     \n\t"			\
>>> +                  "  mvc     0(1,%0),0(%3)   \n\t"			\
>>> +                  "  aghi    %1,1            \n\t"			\
>>> +                  "  aghi    %0,1            \n\t"			\
>>> +                  "  aghi    %2,-1           \n\t"			\
>>> +                  "  j       0b              \n\t"			\
>>> +                  "1:                        \n"			\
>>> +									\
>>> +     : "+a" (pOutput), "+a" (pInput), "+d" (length), "=&a" (tmp)        \
>>
>> That doesn't force %1 to be an even numbered register.
>>
>> ../iconv/loop.c: Assembler messages:
>> ../iconv/loop.c:326: Fatal error: odd numbered general purpose register specified as register pair
> 
> Only %0 is required to be a register pair. This is enforced with the register asm definition above:
> 
> register unsigned char *pOutput asm ("2") = outptr;
> 
> So it looks like GCC is not respecting the register asm in your case?!

GCC can make a copy of the register variable before passing it to the
asm statement.  The “+” in the constraint probably encourages that.

You either have to use a more specific constraint which reflects the
register requirements, or if none exists, drop pOutput from the list of
outputs and rely exclusively on the register value for getting data in
and out of the

Florian