Re: Best compiler/flags combination

Hello, Graham!

quoted

The question is, what compiler is known to produce good code for embedded
PPC boards and what flags should be used? It is desireable that the
binaries still run on PowerPC.

My general approach when starting out is to always use the latest official
released versions, and move to a newer snapshot if you encounter problems.
In particular, the latest official gcc release (gcc-2.95.2) is a better
starting point than the old egcs releases.

Thank you. I'll try it.

This approach works particularily well when you are using the same OS as
the developers (which is probably {i386,alpha}-linux) or when you (or
other people) have time to keep support for your configuration is a good
shape.

You did not mention flags. Maybe my results will be of some interest. I'm
using egcs-1.1.2 native for PowerMAC

-O2                bad code almost everywhere (libcrypt, depmod, bash)
-Os                bad code in tinylogin
-Os -fno-inline    good code (not extensively tested),
                   but it doesn't look like a clean solution
-O2 -mcpu=860 -mmultiple -mstrings -mhard-float
                   good code so far, but libm cannot be compiled
                   (internal error in the compiler)

Probably I'll still have to use
-O2 -mcpu=860 -mmultiple -mstrings -mhard-float

Or should I understand your recommendation so that you don't specify -mcpu
and gcc still produces code running on embedded systems?

Pavel Roskin


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