cmd/internal/obj/amd64: add *blendv* instructions

[gopherbot]

by rayneolivetti:

Currently missing (go1.2rc3) SSE4.1 instructions.

[rsc]

Comment 1:

Labels changed: added go1.3maybe.

[rsc]

Comment 2:

Labels changed: added release-none, removed go1.3maybe.

[rsc]

Comment 3:

Labels changed: added repo-main.

[quasilyte]

https://go-review.googlesource.com/#/c/go/+/57470/
^ implements BLENDPD, BLENDPS, PBLENDW.

Instructions with <XMM0> operand are implemented in CL that can be send on review soon, but it can't be merged until Go 1.11.

I expect this issue to be completely solved in 1.11.

[gopherbot]

Change https://golang.org/cl/97235 mentions this issue: cmd/internal/obj/x86: add missing legacy insts