[Bug optimization/14053] second stage build errors (--with-cpu=601)

["stefaan dot simoens at tiscali dot be" <gcc-bugzilla@gcc.gnu.org>]

------- Additional Comments From stefaan dot simoens at tiscali dot be  2004-02-21 02:00 -------
I've got an Apple PowerMacintosh 7200/75; this has the 601 chip.
I don't know if my kernel (2.4.25-rc1 for the moment) is the best kernel to run 
on a 601; I know my kernel works just fine right now (I compiled the kernel 
myself; the rest of my system is Mandrake 9.1). The kernel is NOT compiled with 
the "601 Bug Workaround" (I had previous versions compiled with and without the 
workaround (which inserts sync and isyncs in before and after some 
instructions) and my system runs fine with or without the workarounds -- I 
chose to run without).

I learned the 601 has PowerPC and POWER instructions; I'm quite sure my 601 
does both. (I think all Mandrake PPC binaries are compiled for PowerPC; but 
when I compile something myself with --mcpu=601 it runs and executes POWER 
instructions (like nabs, cfr my other post). So, I don't think the kernel 
disables the "POWER" instructions.

However, I think there are a few problems with -mcpu=601 [I was using this 
switch to gain the most performance as possible...].

I started my optimization-quest compiling the latest binutils -mcpu=601; the 
build succeeded; all but 5 (ld) tests succeeded (all tests succeeded without 
the -mcpu=601). (The binutils I use right now are the binutils without the -
mcpu=601).

I can't tell for sure the kernel saves and restores the MQ register on "context 
switch" correctly (how can I tell?).
Starting from the "good" assembler code (without -mcpu=601) the 'error' in 
arith-rand-ll.c enters when I replace the divw/mullw/subf with divs/mfmq.
The error doesn't always occur (as far as I can read the code, it uses 
calculations with random numbers...?) -- I ran the compiled 'bad' code for 20 
times and I got 10 times 'Aborted' and the other times the program didn't 
complain at all -- which makes me conclude that it is an error that only 
sometimes happens, an exception?

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14053