RE: [ECOS] Re: long-calls in ARM

["Simpkins, Andy" <Andy dot Simpkins at Transcomm dot uk dot com>]

> -----Original Message-----
> From: Rafael Rodríguez Velilla [mailto:rrv@tid.es]
> Sent: 11 September 2001 07:48
> To: ecos
> Subject: [ECOS] Re: long-calls in ARM
> 
> 
> > Impossible, in fact.  The compiler doesn't know at the time 
> it generates the
> > code what the relative positions in memory will be of the 
> caller and the
> > callee.
> >
> > It would be possible to add code to the linker to 
> synthesize a long call stub if
> > it turned out that a branch was out of range, similar to 
> how glibc's dynamic
> > linker handles R_ARM_PC24 branches between shared 
> libraries.  There would be a
> > run-time performance hit for this, so you'd need to judge 
> whether you'd get better
> > results than by just turning on -mlong-calls and taking the 
> overall hit;
> > obviously it depends on the mix of long and short calls in 
> your application.
> 
> 
>   Just spotting some key functions and adding a pair of 
> attributes to put them in the
> internal memory, and adjusting its calling attributes has 
> halved the time required by
> my system to attend interrupts.
>   The price to pay is that I have had to modify vectors.S, 
> and two prototypes of
> intr.hxx... I'm loosing some compatibility.
>   Obviously, compiling it all with -mlong-calls  will slow my 
> system too much.
> 
>   Maybe some other people are interested in seeing a cdl 
> option that allows them to
> move critical sections into their fastest memory, as me, it 
> wouldn't be difficult (I
> have done it ;) ). 

	yes I would be very interested...

> But I suppose that not many people has 
> such big differences
> between the behavior of their internal memory and their 
> external memory as me.
> 
> 

	Fast EDO RAM internal to the ASIC and slow (8 Wait states) SRAM
Externaly, I have my Interrupt stack running using the EDO RAM, fortunatly
this did not require -mlong-calls because they reside close enough togeather
in the memory map

> 
> 
> 
> --
> Rafael Rodríguez Velilla        rrv@tid.es
> Telefónica I+D          http://www.tid.es
> Telf: +34 - 91 337 4270
> 
> 
>