unpcklbw_asm.cr

def hexdo (a : UInt32)
  ptr_result=Pointer(UInt8).malloc(8, 10_u8)
  add_this=0x2020202020202020_u64
  puts pointerof(add_this).address
  asm("
movl ($0), %eax
movd %eax, %mm0
shrl $$4, %eax
movd %eax, %mm1
punpcklbw %mm0, %mm1
paddb ($2), %mm1
movq %mm1, ($1)
  " :: "r"(pointerof(a).address),"r"(ptr_result.address),"r"(pointerof(add_this)
  ptr_result
end

x=0xA0B1C2D3_u32
sp=Slice.new(hexdo(x), 8)
puts sp.map{|c| c.unsafe_chr }.join