BFI Bitfield insert This instruction 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. BFM 0 1 1 0 0 1 1 0 != 11111 0 0 BFI <Wd>, <Wn>, #<lsb>, #<width> BFM <Wd>, <Wn>, #(-<lsb> MOD 32), #(<width>-1) UInt(imms) < UInt(immr) 1 1 BFI <Xd>, <Xn>, #<lsb>, #<width> BFM <Xd>, <Xn>, #(-<lsb> MOD 64), #(<width>-1) UInt(imms) < UInt(immr) <Wd> Is the 32-bit name of the general-purpose destination register, encoded in the "Rd" field. <Wn> Is the 32-bit name of the general-purpose source register, encoded in the "Rn" field. <lsb> For the "32-bit" variant: is the bit number of the lsb of the destination bitfield, in the range 0 to 31. <lsb> For the "64-bit" variant: is the bit number of the lsb of the destination bitfield, in the range 0 to 63. <width> For the "32-bit" variant: is the width of the bitfield, in the range 1 to 32-<lsb>. <width> For the "64-bit" variant: is the width of the bitfield, in the range 1 to 64-<lsb>. <Xd> Is the 64-bit name of the general-purpose destination register, encoded in the "Rd" field. <Xn> Is the 64-bit name of the general-purpose source register, encoded in the "Rn" field. 2026-03-12 12:23:09 2025-09_rel_asl1