[Bug target/56439] global and local register variables don't work in a useful way -- AVR

[jasonwucj at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56439

Chung-Ju Wu <jasonwucj at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |jasonwucj at gmail dot com

--- Comment #5 from Chung-Ju Wu <jasonwucj at gmail dot com> 2013-02-25 06:32:05 UTC ---
(In reply to comment #4)
> Wouldn't that be a reason /against/ doing this:
> 
>         mov r24,r4
>         lsl r24
>         mov r4,r24
> 
> instead of just lsl r4?

Just guess...

Is that possibly related to zero_extend RTL transformation?
Either in gcc optimization, or the design of machine description?

Try to use this declaration (use 'int' instead of 'char'):
  register unsigned int foo asm ("r4");

Is there any difference on code generation?