On Sun, Aug 15, 2010 at 5:20 AM, Jonathan S. Shapiro <[email protected]> wrote: > On Sat, Aug 14, 2010 at 8:04 PM, Tyler Tricker <[email protected]> wrote: >> >> Is there anyway to provide SIMD without resorting to using just intrinsic >> functions(so applications that want to support them don't need to access >> them)? >> To me regardless of the architecture, operations over arrays and unions >> should be able to support implicit SIMD functionality. > > > I would like that as well. The problem is that even within a major > architecture family, the implementations do not agree about their > implementation of SIMD. AMD and Intel, for example, have differing > functionality. > > One consequence of this is that you can only use SIMD automatically from the > compiler when (a) you're willing to compile to a particular target, or (b) > you're willing to compile multiple versions into a single binary.
I don't think those are the biggest issues. Doing the really trivial stuff like auto-vectorising a[.]=b[.]+c[.]*d[.], particularly in floating point, where you don't have to worry about ranges, is easy. But the single biggest issue, particularly for integer stuff -- which is what a lot of multimedia is, is that assuming your compiler uses the standard definition of optimizaiton that it must be impossible to distringuish the original and the optimized program based on their output, you have a pretty impossible program writing task for the programmer and pattern recognition task for the compiler. Consider the _mm_maddubs_epi16 that featured in the example routine that I posted: it takes a vector of uint8_t's and vector of int8_t's and multiplies corresponding elements, then adds adajcent pairs outputting a vector of int16_t's. Try and write code for that in scalar code that you think a compiler will be able to recognise and convert to the intrinsic. Regards, David Steven Tweed _______________________________________________ bitc-dev mailing list [email protected] http://www.coyotos.org/mailman/listinfo/bitc-dev
