[LLVMdev] More AVX Advice Needed

[David Greene]

I'm working on some of the AVX insert/extract instructions.  They're
stupid.  They do not operate on ymm registers, meaning we have to
use VINSERTF128/VEXTRACTF128 and then do the real operation.

Anyway, I'm looking at how INSERTPS and friends work and noticed that
there are special SelectionDAG nodes for them and corresponding TableGen
dag operators (X86insrtps, for example).

What's the reason for using special dag operators as opposed to intrinsics?

                            -Dave