2.6.3.3.2 Register with Optional Shift

You specify an Operand2 register in the form:

Rm {, shift}

where:

Rm: is the register holding the data for the second operand.
shift: is an optional shift to be applied to Rm. It can be one of:
- ASR #n: arithmetic shift right n bits, 1 ≤ n ≤ 32
- LSL #n: logical shift left n bits, 1 ≤ n ≤ 31
- LSR #n: logical shift right n bits, 1 ≤ n ≤ 32
- ROR #n: rotate right n bits, 1 ≤ n ≤ 31
- RRX: rotate right one bit, with extend

-: if omitted, no shift occurs, equivalent to LSL #0.

If you omit the shift, or specify LSL #0, the instruction uses the value in Rm.

If you specify a shift, the shift is applied to the value in Rm, and the resulting 32-bit value is used by the instruction. However, the contents in the register Rm remains unchanged. Specifying a register with shift also updates the carry flag when used with certain instructions. For information on the shift operations and how they affect the carry flag, refer to 2.6.3.4 Shift Operations.