[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [f-cpu] Relative branch



On Wed, Dec 11, 2002 at 11:29:38AM +0100, devik wrote:
> Just short idea, I was found that in compiled
> code for fcpu is missing shorter/faster jump.
> 
> Why dont we have jump which instead of registers
> to use as return address save and target adres
> have instead 12bit immediate which would REPLACE
> lower 8 bits (for example) of IP.

Umh. That will require heavy alignments, which may lead to increasing
aliasing problems. And it's hard to handle inside the compiler and
linker. You have to know in advance where the page boundaries are - that
is, every object file will need 4k alignment. The resulting executable
will contain lots of holes, and while the size of the executed code
decreases, the file size will actually increase, resulting in more (and
more frequent) memory loads which slow down execution. It's a waste of
space and memory bandwidth, IMHO.

-- 
 Michael "Tired" Riepe <Michael.Riepe@stud.uni-hannover.de>
 "All I wanna do is have a little fun before I die"
*************************************************************
To unsubscribe, send an e-mail to majordomo@seul.org with
unsubscribe f-cpu       in the body. http://f-cpu.seul.org/