[llvm-dev] Complex proposal v2

[Krzysztof Parzyszek via llvm-dev]

> -----Original Message-----
> From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of David Greene
> via llvm-dev
> Sent: Thursday, August 29, 2019 10:05 AM
> To: llvm-dev <llvm-dev at lists.llvm.org>
> Subject: [EXT] [llvm-dev] Complex proposal v2
>
> [...]
>
> llvm.extractreal.* - Overloaded intrinsic to create a vector of
>                      floating-point type from the real portions of a
>                      vector of complex (not all variants shown)
>
> declare v4f32 @llvm.extractreal.v4c32(v4c32 %val) declare v4f64
> @llvm.extractreal.v4c64(v4c64 %val)
>
> llvm.extractimag.* - Overloaded intrinsic to create a vector of
>                      floating-point type from the imaginary portions
>                      of a vector of complex (not all variants shown)
>
> declare v4f32 @llvm.extractimag.v4c32(v4c32 %val) declare v4f64
> @llvm.extractimag.v4c64(v4c64 %val)

I think that "cunzip" returning a pair of vectors would be better.  If both results are needed, they could usually be generated by a single instruction corresponding to some kind of a shuffle, but in order to generate that instruction, the backend would have to see both of the "extract*" intrinsics.  With cunzip, if one only wants a single part, they can ignore the other element of the pair.

-Krzysztof