On Sun, 9 Feb 2014, Stephen N Chivers wrote: > James Yang <james.y...@freescale.com> wrote on 02/08/2014 07:49:40 AM: > > > From: James Yang <james.y...@freescale.com> > > To: Gabriel Paubert <paub...@iram.es> > > Cc: Stephen N Chivers <schiv...@csc.com.au>, Chris Proctor > > <cproc...@csc.com.au>, <linuxppc-dev@lists.ozlabs.org> > > Date: 02/08/2014 07:49 AM > > Subject: Re: arch/powerpc/math-emu/mtfsf.c - incorrect mask? > > > > On Fri, 7 Feb 2014, Gabriel Paubert wrote: > > > > > Hi Stephen, > > > > > > On Fri, Feb 07, 2014 at 11:27:57AM +1000, Stephen N Chivers wrote: > > > > Gabriel Paubert <paub...@iram.es> wrote on 02/06/2014 07:26:37 PM: > > > > > > > > > From: Gabriel Paubert <paub...@iram.es> > > > > > To: Stephen N Chivers <schiv...@csc.com.au> > > > > > Cc: linuxppc-dev@lists.ozlabs.org, Chris Proctor > <cproc...@csc.com.au> > > > > > Date: 02/06/2014 07:26 PM > > > > > Subject: Re: arch/powerpc/math-emu/mtfsf.c - incorrect mask? > > > > > > > > > > On Thu, Feb 06, 2014 at 12:09:00PM +1000, Stephen N Chivers wrote: > > > > > > With the above mask computation I get consistent results for > > > > > > both the MPC8548 and MPC7410 boards. > > > > > > > > > > > > Am I missing something subtle? > > > > > > > > > > No I think you are correct. This said, this code may probably be > > > > optimized > > > > > to eliminate a lot of the conditional branches. I think that: > > > > > > If the compiler is enabled to generate isel instructions, it would not > > use a conditional branch for this code. (ignore the andi's values, > > this is an old compile) > > > From limited research, the 440GP is a processor > that doesn't implement the isel instruction and it does > not implement floating point. > > The kernel emulates isel and so using that instruction > for the 440GP would have a double trap penalty.
Are you writing about something outside the scope of this thread? OP was using MPC8548 not a 440GP. The compiler should not be using or targeting 8548 for a 440GP so having to emulate isel shouldn't be an issue because there wouldn't be any. (The assembly listing I posted was generated by gcc targeting 8548.) Anyway, I had measured the non-isel routines to be faster and that works without illop traps. > Correct me if I am wrong, the isel instruction first appears > in PowerPC ISA v2.04 around mid 2007. isel appeared in 2003 in the e500 (v1) core that is in the MPC8540. The instruction is Power ISA 2.03 (9/2006). _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
