On 08.05.2013, at 12:34, Torbjorn Granlund wrote: > Aurelien Jarno <aurel...@aurel32.net> writes: > > You have to declare the L bit as invalid, so that trying to execute a > 64-bit cmp* instruction on a 32-bit CPU causes an invalid instruction > exception. > > Don't people read what I write?
At least on my e500mc machine I happen to have handy, the following instruction gives me an illegal instruction exception: 10000320: 2f a0 00 00 cmpi cr7,1,r0,0 So for 32bit CPU types we have to mark the L bit invalid which means we always get into the branches that take us to cmp32. For 64bit capable CPUs we obviously want to honor the L bit even when running in 32bit mode (MSR.SF=0), as that's what real CPUs do. Alex
