CMP (immediate) -- AArch32

CMP (immediate)

Compare (immediate) subtracts an immediate value from a register value. It updates the condition flags based on the result, and discards the result.

It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 and T2 ) .

constant n = UInt(Rn); constant imm32 = A32ExpandImm(imm12);

15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0	0	1	0	1	Rn			imm8

constant n = UInt(Rn); constant imm32 = ZeroExtend(imm8, 32);

15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
1	1	1	1	0	i	0	1	1	0	1	1	Rn				0	imm3			1	1	1	1	imm8

CMP{<c>}.W <Rn>, #<const> // (<Rd>, <const> can be represented in T1)

constant n = UInt(Rn); constant imm32 = T32ExpandImm(i:imm3:imm8); if n == 15 then UNPREDICTABLE;

For more information about the constrained unpredictable behavior, see Architectural Constraints on UNPREDICTABLE behaviors.

<c>	See Standard assembler syntax fields.

<q>	See Standard assembler syntax fields.

<Rn>	For encoding A1: is the general-purpose source register, encoded in the "Rn" field. The PC can be used, but this is deprecated.
	For encoding T1: is a general-purpose source register, encoded in the "Rn" field.
	For encoding T2: is the general-purpose source register, encoded in the "Rn" field.

<imm8>

Is a 8-bit unsigned immediate, in the range 0 to 255, encoded in the "imm8" field.

<const>	For encoding A1: an immediate value. See Modified immediate constants in A32 instructions for the range of values.
	For encoding T2: an immediate value. See Modified immediate constants in T32 instructions for the range of values.

if ConditionPassed() then EncodingSpecificOperations(); constant (result, nzcv) = AddWithCarry(R[n], NOT(imm32), '1'); PSTATE.<N,Z,C,V> = nzcv;

If CPSR.DIT is 1, this instruction has passed its condition execution check, and does not use R15 as either its source or destination:

The execution time of this instruction is independent of:
- The values of the data supplied in any of its registers.
- The values of the NZCV flags.
The response of this instruction to asynchronous exceptions does not vary based on:
- The values of the data supplied in any of its registers.
- The values of the NZCV flags.

Internal version only: isa v01_31, pseudocode v2024-03_rel ; Build timestamp: 2024-03-25T10:05