Re: FW: Inline assembly, clobber registers, ask for help

[Tamas Nagy <nagytam at web dot de>]

Thanks for your comments.

I converted the code not to use predefined general registers, and it seems it is working now, even with optimizations. Apart from this, I would like to learn more about this topic.

You mentioned that gcc needs 1 or two registers for saving/restoring clobbered registers. 
Why gcc tries to do this in every case?  I could imagine a lot of code, where an inline assembly routine could use registers and after it it has not to be restored. E.g. later initialized with a contant... 
Another solution would be to use POPA/PUSHA if there are no general registers available. Currently gcc miscompiles the code in case of optimizations, if I understood/experience right. 

In general, what kind of tasks are gcc doing prior/middle/after to an inline assembly  code, when optimizations are enabled? (Is there any documentation to read more about this? Thanks for pointing out in a private mail the gcc manual 'Extensions to the C language' chapter.)

I use gcc version 3.2.2 20030109. I assume ECX as a member of general register class, but gcc provides the following error message:
"can't find a register in 'GENERAL_REGS while reloading asm".
EAX, EBX are fine ECX not.

I really appreciate your help,
Tamas
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