So is there a FAQ or HOWTO on the issues involved in porting little endian to big endian software somewhere ? I haven't seen it yet after some looking.
Thanks Joe Dery > Hi Joe, > > > My senior design group is working with a IBM Walnut board > > with the 200 MHz 405GP r3. We have the linux kernel and > > target filesystem taken from the Nov. 26, 2000 sources. > > The board boots Linux from NFS flawlessly after compilation > > using the CDK 1.0 8xx toolkit. > > > > Our project objectives include compiling the ITU-T G.723.1 > > (Voice over IP) standard C source code. We are (again) using > > the powerpc-linux-gcc included with the MV CDK 1.0 tools for > > PowerPC 8xx-based machines. > > > > I understand that an updated devkit is available, but since > > our budget cannot touch the subscription fees needed to > > obtain the MontaVista toolkit for the 405GP. > > > > Enough background already. The problem arises in that > > when we compile the VoIP source code and run it on the > > PowerPC, the output of the encoder and decoder is wrong. > > When the same code is compiled for our host machine > > (using i386 gcc) the output is ok. This C code involves a > > lot of speed-oriented fixed-point mathematics - that is, a lot > > of multiplies and shifts (to avoid divides) Just searching for the > > >> and << operators in the kernel source doesn't bring up much. So > > to me this may be the culprit. Sorry to make this so vague - I am > > just hoping that someone has seen problems with math/DSP oriented > > programs before and can suggest something! > > If I had to put money on a bet where the problem might be located I > would say your VoIP en-/decoder program is not written properly for a > big endian machine. Especially reading data from/writing to memory via > pointers can cause all kinds of errors. Please find a known good big > endian machine somewhere and see if the algorithms work properly. If > not kick the developer of the beast and fix it. I've seen a lot of > integer DSP code to break when ported from little to big endian. > > Don't blame CPU or compiler too early, C doesn't abstract endianess > issues completely - so they might visible. > > > Also, I wanted to verify the size of the variable types in the > > gcc compiler for the PowerPC. Please correct me if I'm > > wrong. > > > > int - 32 bit signed integer > > short - 16 bit signed integer > > correct for PPC. > short always 16 > long always 32 > long long always 64 > int = machine word size > > I hope I could point you in the proper direction, > Rolf > ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
