[Patch, AVR]: Fix PR33049 (implement extzv)

Denis Chertykov chertykov@gmail.com
Tue Jun 21 13:26:00 GMT 2011

2011/6/21 Georg-Johann Lay <avr@gjlay.de>:
> Denis Chertykov schrieb:
>> 2011/6/21 Georg-Johann Lay:
>>> Ok.  d_register_operand or satisfies_constraint_d would do.  But I
>>> preferred to introduce a new constraint for 4 and avoid splitting
>>> *extzv altogether to keep it simple.  Complexity of splitting is not a
>>> real advantage over writing things down directly.
>>> As avr is running out of constraint letters, I started 3-letter
>>> constraints 'Y**' in the style of bfin.  Would be nice if 'K' was not
>>> already occupied or could be deprecated (is'n not really useful in
>>> inline asm)...
>> Better to choose starting letter different to pointer register names X,Y,Z.
>> May be better to use underscore '_' ?
>> Denis.
> My preference would be to change 'K' to 'K02' and thus deprecate 'K'.
> Other letters are 'A', 'B', 'C', D', 'R', 'S', 'T', 'U', 'W', 'Z'.
> I do not like '_' as constraint.
> 'R' might be needed in the future for more register constraints (r24,
> r24-r25, r22-25, ...) and 'R' is a nice prefix.
> 'C' looks appealing for constant.

I'm vote for 'C'.


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