On Tuesday 31 October 2006 22:31, Laurent Desnogues wrote: > Paul Brook a écrit : > > Replacing the pregenerated blocks with hand written assembly isn't > > feasible. Each target has its own set of ops, and each host would need > > its own assembly implementation of those ops. Multiply 11 targets by 11 > > hosts and you get a unmaintainable mess :-) > > Shouldn't you have 11+11 and not 11*11, given your intermediate > representation? And of these 11+11, 11 have to be written > anyway (target). Or did I miss something?
If you use qops (which is a target and host independent intermediate representation) it's 11 + 11. If you just replace the existing dyngen op.c with hand written assembly it's 11 * 11. > > On RISC targets like ARM most instructions don't set the condition codes, > > so we don't bother doing this. > > Except for ARM Thumb ISA which always sets flags. ARM is a bad > RISC example :) Bah. Details :-) > I was wondering if you did some profiling to know how much time > is spent in disas_arm_insn. Of course the profiling results > would be very different for a Linux boot or a synthetic benchmark The qop generator does add some overhead to the code translation. I haven't done proper benchmarks, but in most cases it doesn't seem to be too bad (maybe 10%). I'm hoping we can get most of that back. > (which makes me think that you don't support MMU, do you?). qemu does implement a MMU. Currently this still uses the dyngen code, but that's fixable. > There is a very nice trick to speed up decoding of ARM > instructions: pick up bits 20-27 and 4-7 and you (almost) get > one instruction per case entry; of course this means using a > generator to write the 4096 entries, but the result was good for > my interpreted ISS, reaching 44 M i/s on an Opteron @2.4GHz > without any compiler dependent trick (such as gcc jump to labels). qemu generally gets 100-200MIPS on my 2GHz Opteron. Paul _______________________________________________ Qemu-devel mailing list Qemu-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/qemu-devel
