[LLVMdev] More AVX Advice Needed

Eli Friedman eli.friedman at gmail.com
Wed Dec 2 14:51:33 PST 2009

On Wed, Dec 2, 2009 at 2:44 PM, David Greene <dag at cray.com> wrote:
> 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?

INSERTPS isn't an intrinsic because there's a standard way to
represent the operation, and we try to avoid adding intrinsics when


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