ccmp

Conditional Compare (Immediate)

CCMP <Wn>, #<imm>, #<nzcv>, <cond>

Compares register with immediate if condition is true.

Details

Conditional Compare (Immediate), 32-bit. If the condition is true, performs an arithmetic compare of Wn - imm5, otherwise loads the NZCV flags with the immediate value nzcv. The comparison sets or clears N, Z, C, V flags accordingly. AArch64-only instruction.

Pseudocode Operation

if ConditionHolds(cond) then temp ← Wn - imm5; N ← temp[31]; Z ← (temp == 0); C ← NOT(BorrowFrom(Wn, imm5)); V ← SignedOverflow(Wn, -imm5) else N ← nzcv[3]; Z ← nzcv[2]; C ← nzcv[1]; V ← nzcv[0]

Example

CCMP w1, #16, #nzcv, cond

Encoding

Binary Layout
0
1
1
11010010
imm5
cond
1
0
Rn
0
nzcv
 
Format Cond Comp
Opcode 0x7A400800
Extension Base

Operands

  • Wn
    Reg
  • imm
    Imm
  • nzcv
    Flags
  • cond
    Condition

Reference (Arm A64 ISA)

Instruction Forms

Encoding Instruction ISA Bit pattern
0x7A400800 CCMP <Wn>, #<imm>, #<nzcv>, <cond> A64 0 | 1 | 1 | 11010010 | imm5 | cond | 1 | 0 | Rn | 0 | nzcv
0xFA400800 CCMP <Xn>, #<imm>, #<nzcv>, <cond> A64 1 | 1 | 1 | 11010010 | imm5 | cond | 1 | 0 | Rn | 0 | nzcv
0x7A400000 CCMP <Wn>, <Wm>, #<nzcv>, <cond> A64 0 | 1 | 1 | 11010010 | Rm | cond | 0 | 0 | Rn | 0 | nzcv
0xFA400000 CCMP <Xn>, <Xm>, #<nzcv>, <cond> A64 1 | 1 | 1 | 11010010 | Rm | cond | 0 | 0 | Rn | 0 | nzcv

Description

Conditional Compare (immediate) sets the value of the condition flags to the result of the comparison of a register value and an immediate value if the condition is TRUE, and an immediate value otherwise.

Operation

if ConditionHolds(cond) then
    bits(datasize) operand1 = X[n, datasize];
    bits(datasize) operand2;
    operand2 = NOT(imm);
    (-, flags) = AddWithCarry(operand1, operand2, '1');
PSTATE.<N,Z,C,V> = flags;