-march prescott: GENERAL_REGS error; but -msseX Ok ?

[sean darcy]

----Original Message Follows----
From: Falk Hueffner
................
>>So is the only reason prescott doesn't work is prefetch-sse.

>No, that is a red herring. The different instruction scheduling causes
>the register allocator to randomly fail or not.

I don't know what you mean by random, but I just tried to build mythtv 10 
times with each set of cflags. The set with -mtune=prescott always bombed, 
the other always worked.

So what does mtune cause gcc to do that the other set of cflags doesn't? How 
does mtune change the instruction scheduling if it's not in config/i386.c?

>There's no way for us
>to fix this reliably, the asm must be changed to constrain the
>register allocator less.

Yeh. I read the list.

sean