SBFM

Signed Bitfield Move is usually accessed via one of its aliases, which are always preferred for disassembly.

If <imms> is greater than or equal to <immr>, this copies a bitfield of (<imms>-<immr>+1) bits starting from bit position <immr> in the source register to the least significant bits of the destination register.

If <imms> is less than <immr>, this copies a bitfield of (<imms>+1) bits from the least significant bits of the source register to bit position (regsize-<immr>) of the destination register, where regsize is the destination register size of 32 or 64 bits.

In both cases the destination bits below the bitfield are set to zero, and the bits above the bitfield are set to a copy of the most significant bit of the bitfield.

This instruction is used by the aliases ASR (immediate), SBFIZ, SBFX, SXTB, SXTH, and SXTW.

integer d = UInt(Rd); integer n = UInt(Rn); integer datasize = if sf == '1' then 64 else 32; boolean inzero; boolean extend; integer R; integer S; bits(datasize) wmask; bits(datasize) tmask; case opc of when '00' inzero = TRUE; extend = TRUE; // SBFM when '01' inzero = FALSE; extend = FALSE; // BFM when '10' inzero = TRUE; extend = FALSE; // UBFM when '11' UNDEFINED; if sf == '1' && N != '1' then UNDEFINED; if sf == '0' && (N != '0' || immr<5> != '0' || imms<5> != '0') then UNDEFINED; R = UInt(immr); S = UInt(imms); (wmask, tmask) = DecodeBitMasks(N, imms, immr, FALSE);