Re: FW: eCos for MPC55xx

[Jonathan Larmour <jifl@jifvik.org>]

Gerster Jochen-B01096 wrote:
> 
> The problem is: The POWERPC gcc compiler (allocated from the ecos site)
> optimize memcpy calls with small length, instead it uses its own inline
> function without taking care of aligned access.

If it did not work for unaligned accesses on PowerPC in general, then this 
would have been discovered years ago.

Perhaps have the semantics of an opcode in the MPC55xx changed so that 
something that used to work for all PowerPC now only works on aligned 
addresses? If so that wouldn't be good, but it's not beyond the realms of 
possibility.

> This is a very very big
> problem using the TCP/IP stack because the IP-address is 4byte so the
> gcc optimize and the offset of the IP-address in the different
> protocol-headers varies. This ends in a exception :(
> 
> So I asking me now: I'm the only one with this problem? How do you solve
> this problem, perhaps a compiler flag?

Theoretically -fno-builtin can be used to disable GCC's optimisations if 
they are genuinely at fault. But I'm not sure. Have you tried a small 
testcase? And if so have you looked at the assembler GCC is producing?

Jifl
-- 
--["No sense being pessimistic, it wouldn't work anyway"]-- Opinions==mine