On 31 July 2018 at 11:49, Timothe Litt <l...@ieee.org> wrote: > > On 31-Jul-18 10:08, Paul Koning wrote: > > On Jul 31, 2018, at 9:33 AM, Robert Armstrong <b...@jfcl.com> <b...@jfcl.com> > wrote: > > > FWIW, this may also say something about the quality of the code generation > in gcc for ARM vs x86 processors, or it may even say something about the > relative efficiency of those two architectures. > > One thing worth doing is to use the latest gcc. Code generation keeps > improving, and it's likely that architectures such as ARM see significant > benefits in newer releases. > > > > > Bob's SimH shows: > > Compiler: GCC 6.3.0 20170516 > > The latest gcc is 8.1.0. > > It's a bit of a pain to build (I did it recently), but less so than in > years past. > > On a Pi, it will take quite a while. Be sure to use the latest > dependencies - gmp, mpc, mpfr. And put in some place like /usr/local - you > don't want to replace the system compiler. > > Read http://gcc.gnu.org/wiki/InstallingGCC & https://gcc.gnu.org/install/ > index.html. > > I haven't played with isl - it may help, or it may expose new issues. > > You may be better off building a cross-compiler & building on a fast x86 > or other platform if you have one. Besides computes, I/O on the PI can be > pretty slow - USB is not a high-performance bus. Especially if you need a > bunch of hubs. > > You also may need the latest binutils - if not for the build, for using > the compiler. Somewhere between the version I used previously and the new > one, the object file format was enhanced incompatibly. > > ARM is a RISCish architecture, x86 is a very CISC one, burdened with a lot > of backward compatibility. Under the hood, it uses a lot of clever > optimizations. Both are moving targets, as are their compilers. (GCC > isn't the only choice. Don't forget to try ICC if you want Intel's take on > optimized code for their CPUs. And Clang is coming along.) Don't open the > religious war over "relative efficiency"; the only thing that matters is > whether code that you care about has performance that you deem adequate. > > Have fun. >
I did a writeup a while back about various compilers and SIMH on x86, here is the link from the archive: http://mailman.trailing-edge.com/pipermail/simh/2015-December/014102.html Profile-guided feedback is extremely helpful for SIMH. If you are able to recompile SIMH for your workload using feedback, the gains are extremely significant. -Henry
_______________________________________________ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
