On 01.06.2010, at 00:40, Paul Mackerras wrote: > On Mon, May 31, 2010 at 09:59:13PM +0200, Andreas Schwab wrote: > >> Instead of instantiating a whole thread_struct on the stack use only the >> required parts of it. > > ... > >> +_GLOBAL(kvm_cvt_fd) >> + lfd 0,0(r5) /* load up fpscr value */ >> + MTFSF_L(0) >> + lfs 0,0(r3) >> + stfd 0,0(r4) >> + mffs 0 >> + stfd 0,0(r5) /* save new fpscr value */ >> + blr >> + >> +_GLOBAL(kvm_cvt_df) >> + lfd 0,0(r5) /* load up fpscr value */ >> + MTFSF_L(0) >> + lfd 0,0(r3) >> + stfs 0,0(r4) >> + mffs 0 >> + stfd 0,0(r5) /* save new fpscr value */ >> + blr > > I re-read the relevant part of the PowerPC architecture spec > yesterday, and it seems pretty clear that the FPSCR doesn't affect the > behaviour of lfs and stfs, and is not affected by them. So in fact 4 > out of the 7 instructions in each of those procedures are unnecessary > (and similarly for the cvt_fd/df used in the alignment fixup code). So the rounding control field is not used on lfs? Interesting. I couldn't find a reference to it being used or modified either though. Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
