ARM Instruction Set: Comparative Instructions

Assembler input:

CMN|CMP|TEQ|TST <first>,<shift>

Assembler output:

High byte as standard
Sixth nybble contains comparative subinstruction code and S flag
  Bits 21-23 (3-bit cardinal) are comparative subinstruction code
  Bit 20 is S flag
Fifth nybble is first register
Fourth nybble is 0, or F if P flag specified
Bottom three nybbles depend on base instruction grouping

If base instruction code is 0 or 1 then:

Bit 4 determines whether shift factor is a register or a constant
  0  Shift factor is a constant
       Bits 7-15 (5-bit cardinal) are shift factor
       Bits 5-6 are barrel shifter subinstruction code
  1  Shift factor is a register
       Third nybble is register containing shift factor
       Bit 7 is 0
       Bits 5-6 are barrel shifter subinstruction code
Low nybble is second register

If base instruction code is 2 or 3 then:

Bottom three nybbles are an immediate constant

The following are valid subinstruction codes:

Value  Base instruction mnemonic
0      TST
1      TEQ
2      CMP
3      CMN