rsc

Reverse Subtract with Carry (A32)

RSC{S}<c> <Rd>, <Rn>, <Operand2>

Calculates Rd = Operand2 - Rn - NOT(Carry).

Pseudocode Operation

result ← Operand2 - Rn - NOT(C)
Rd ← result
if S == 1 then
  N ← result[31]
  Z ← (result == 0)
  C ← NOT(Borrow)
  V ← (Operand2[31] != Rn[31]) AND (Operand2[31] != result[31])
endif

Example

RSC r0, r1, r2

Encoding

Binary Layout

cond

31:28

0010

27:24

111

23:21

19:16

15:12

imm12

11:0

Format Data Proc

Opcode 0x02E00000

Extension A32 (Base)

Operands

Rd
Destination general-purpose register
Rn
First source / base general-purpose register
Operand2
Flexible second operand (register or shifted register)

Reference

View in Arm A64 ISA Reference ↗ Arm AArch32 ISA

Instruction Forms

Encoding	Instruction	ISA	Bit pattern
0x02E00000	RSC{<c>}{<q>} {<Rd>,} <Rn>, #<const>	A32	cond \| 0010 \| 111 \| 0 \| Rn \| Rd \| imm12
0x00E00060	RSC{<c>}{<q>} {<Rd>,} <Rn>, <Rm>, RRX	A32	cond \| 0000 \| 111 \| 0 \| Rn \| Rd \| 00000 \| 11 \| 0 \| Rm
0x00E00000	RSC{<c>}{<q>} {<Rd>,} <Rn>, <Rm> {, <shift> #<amount>}	A32	cond \| 0000 \| 111 \| 0 \| Rn \| Rd \| imm5 \| stype \| 0 \| Rm
0x00E00010	RSC{<c>}{<q>} {<Rd>,} <Rn>, <Rm>, <shift> <Rs>	A32	cond \| 0000 \| 111 \| 0 \| Rn \| Rd \| Rs \| 0 \| stype \| 1 \| Rm

Description

Reverse Subtract with Carry (immediate) subtracts a register value and the value of NOT (Carry flag) from an immediate value, and writes the result to the destination register. If the destination register is not the PC, the RSCS variant of the instruction updates the condition flags based on the result. The field descriptions for <Rd> identify the encodings where the PC is permitted as the destination register. ARM deprecates any use of these encodings. However, when the destination register is the PC:

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    (result, nzcv) = AddWithCarry(NOT(R[n]), imm32, PSTATE.C);
    if d == 15 then
        if setflags then
            ALUExceptionReturn(result);
        else
            ALUWritePC(result);
    else
        R[d] = result;
        if setflags then
            PSTATE.<N,Z,C,V> = nzcv;

rsc