func avx2gatherValid(ctxt *obj.Link, p *obj.Prog) bool {
	// If any pair of the index, mask, or destination registers
	// are the same, illegal instruction trap (#UD) is triggered.
	index := regIndex(p.GetFrom3().Index)
	mask := regIndex(p.From.Reg)
	dest := regIndex(p.To.Reg)
	if dest == mask || dest == index || mask == index {
		ctxt.Diag("mask, index, and destination registers should be distinct: %v", p)
		return false
	}