On Friday, 28 October 2016 02:37:38 UTC+2, Erwin Driessens wrote: > I'd love to see SIMD intrinsics in the Go compiler(s), even if it would mean separate packages for all the architectures. I'm not experienced enough to tell how far one could get with designing a cross-platform set of intrinsics instructions?
There are attempts at generalized SIMD out there (google "web simd" for instance), but while they may be good for web, I think they fall short for a compiled language. The problem is that they either support a lowest common denominator or have to fall back to slow reference implementations. Take for instance the PSHUFB instruction, which allows a very fast [16]byte lookup in SSSE3 capable machines. This is helpful in various ways, but if it isn't available, it will have to commit the XMM register to memory and do 16 lookups, which is at least an order of magnitude slower than using the SIMD. Similarly, RSQRT (low precision reciprocal of the square root) instruction allows a "shortcut", but if it isn't available on your architecture, it will likely be very expensive. Furthermore keeping it close to the C instrinsics would also make porting existing code easier, which I can only see at a positive. However, adding it is not a trivial task, but with the recent compiler rewrite, it has become much more feasible. There are still issues that should be worked out, like forced constant parameters, switching between 2 and 3 parameter (VEX) instructions with compiler flags, intrinsic types, etc, and of course the entire thing of defining the intrinsics and supplying that information to the compiler. Using the hardware when it is available, falling back on emulation when not? > As you might be able to tell, I am not a big fan of emulation for other than testing purposes. While it might be reasonable in some cases, I find that a "clean" Go version is mostly better than an emulated intrinsics version. I could go on. If you haven't already seen it, there is some good ideas here: https://groups.google.com/forum/#!topic/golang-nuts/yVOfeHYCIT4 /Klaus -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
