When speeds are equivalent, or very close, I usually prefer auto
vectorized code to explicit SIMD/__vector code as it's easier to
read. (on the downside you have to guard against compiler
code-gen performance regressions)
One oddity I've noticed is that I sometimes need to use
pragma(inline, *false*) in order to get ldc to "do the right
thing". Apparently the compiler sees the costs/benefits
differently in the standalone context.
More widely known techniques that have gotten people over the
serial/SIMD hump include:
1) simplified indexing relationships
2) known count inner loops (chunkify)
3) static foreach blocks (manual inlining that the compiler
"gathers")
I'd be interested to hear from others regarding their auto
vectorization and __vector experiences. What has worked and what
hasn't worked in your performance sensitive dlang code?
