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