[GlobalISel][X86] Support vector type G_EXTRACT selection.

[igorb]

Summary

Support vector type G_EXTRACT selection. For now G_EXTRACT marked as legal for any type, so nothing to do in legalizer.
Split from https://reviews.llvm.org/D33665

[guyblank]

lib/Target/X86/X86InstructionSelector.cpp

706 ↗

(On Diff #101617)

does it make sense not to give up here?

not sure when the emit would fail, but we could try to generate a vextract instead.

717 ↗

(On Diff #101617)

if(..)
  return false;

[igorb]

• rebase

lib/Target/X86/X86InstructionSelector.cpp

706 ↗

(On Diff #101617)

I can't test case when the emit fail , so i prefare to give up

717 ↗

(On Diff #101617)

I think in this case it will complicate the code

[guyblank]

lgtm