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Re: ARM thumb: why call_via_rX?
On Fri, 2002-01-25 at 13:35, Phil Blundell wrote:
> > Our CPU has an internal 8K static (fast) RAM, and external (slow) Flash.
> > So my collegue had the idea of copying the most time-consuming code into
> > the fast on chip RAM. So, of course, calls between non-copied and copied
> > code with bl (such as calling call_via_rX) fail horribly.
>
> Ah, I see. If this copying is done just once at startup and then the
> map stays fixed, you could write a custom linker script defining the
> right memory regions, and then PC-relative branches would "just work"
> (so long as the regions aren't too far apart, anyway).
Wouldn't work, I think, as (a) our Flash is mapped at 0x90000000 and the
SRAM at 0x0, and (b) at link time I don't know where in the Flash romfs
my binary is going to be. But for the simple case this would probably be
the best idea.
I thought about putting the SRAM routines in a special section, too, but
this falls flat in our case as we're using flat binaries which don't
know nuffin about sections.
greets from Zürich
-- vbi