Ready for review: new std.uni

[David Nadlinger]

On Monday, 14 January 2013 at 09:02:25 UTC, Walter Bright wrote:
>> Yet *all* the big compiler vendors (Microsoft, Intel, GCC, 
>> LLVM) seem to find it
>> necessary to spend considerable amounts of effort on improving 
>> their heuristics
>> for the indeed quite problematic optimization process you 
>> describe.
>
> The fundamental problem they face is they cannot change the 
> language - they have to work with bog standard code that has no 
> notion of SIMD.

They *are* changing the language using SIMD intrinsics and 
built-in types. It might be that D can do a somewhat nicer job at 
that by standardizing them and using less cryptic names, but the 
fundamental concept remains the same.

And again, you don't have to convince me about the problems 
inherent to auto-vectorization, I'm well aware of them. I'm just 
pointing out that despite these obstacles, compiler vendors are 
still trying to implement it, probably because writing vector 
code is fundamentally difficult (as you mentioned, you can easily 
shoot yourself in the foot in many ways, performance-wise), and 
you can't justify just not using the vector units on today's 
chips.

It's not that I think __vector, core.simd and friends would be a 
*bad* idea. But your general dismissal of auto-vectorization 
seems a bit too quick and convenient to me.

David