Bitfield Insert copies a bitfield of <width> bits from the least significant bits of the source register to bit position <lsb> of the destination register, leaving the other destination bits unchanged.

位域插入将<width>位的位域从源寄存器的最低有效位复制到目标寄存器的位位置<lsb>，保持其他目标位不变。

32-bit variant
    Applies when sf == 0 && N == 0.
    BFI <Wd>, <Wn>, #<lsb>, #<width>

    is equivalent to
    BFM  <Wd>, <Wn>, #(-<lsb> MOD 32), #(<width>-1)
    and is the preferred disassembly when UInt(imms) < UInt(immr).

64-bit variant
    Applies when sf == 1 && N == 1.
    BFI <Xd>, <Xn>, #<lsb>, #<width>

    is equivalent to
    BFM  <Xd>, <Xn>, #(-<lsb> MOD 64), #(<width>-1)
    and is the preferred disassembly when UInt(imms) < UInt(immr).

  4005a0:       d2800000        mov     x0, #0x0                        // #0
  4005a4:       b94023e1        ldr     w1, [sp, #32]
  4005a8:       b3407c20        bfxil   x0, x1, #0, #32
  4005ac:       b94027e1        ldr     w1, [sp, #36]
  4005b0:       b3607c20        bfi     x0, x1, #32, #32        // x0=取x1的高32位