Data Processing Instructions Overview for ARM Processors

* Question

What types of ARM data processing instructions are there?

* Answer

ARM processors support a variety of data processing instructions, which perform operations on registers and immediate values. These instructions can be categorized into the following types:

Table of Contents

1. Arithmetic Instructions

These perform basic arithmetic operations:

ADD– Addition (Rd = Rn + Operand2)
ADC– Addition with carry (Rd = Rn + Operand2 + Carry)
SUB– Subtraction (Rd = Rn – Operand2)
SBC– Subtraction with carry (Rd = Rn – Operand2 – NOT Carry)
RSB– Reverse subtract (Rd = Operand2 – Rn)
RSC– Reverse subtract with carry (Rd = Operand2 – Rn – NOT Carry)

2. Logical Instructions

These perform bitwise logical operations:

AND– Bitwise AND (Rd = Rn & Operand2)
ORR– Bitwise OR (Rd = Rn | Operand2)
EOR– Bitwise Exclusive OR (Rd = Rn ^ Operand2)
BIC– Bitwise Clear (Rd = Rn & ~Operand2)

3. Comparison Instructions

These set condition flags based on the result but do not store the result:

CMP– Compare (Rn – Operand2)
CMN– Compare with negate (Rn + Operand2)
TST– Test bits using AND (Rn & Operand2)
TEQ– Test bits using XOR (Rn ^ Operand2)

4. Shift and Rotate Instructions

These modify register values using shift or rotate operations:

LSL (Logical Shift Left)– Shifts bits left, filling with zeros.
LSR (Logical Shift Right)– Shifts bits right, filling with zeros.
ASR (Arithmetic Shift Right)– Shifts bits right, preserving the sign bit.
ROR (Rotate Right)– Rotates bits right without carry.
RRX (Rotate Right with Extend)– Rotates bits right through the carry flag.

5. Multiply and Multiply-Accumulate Instructions

Used for multiplication operations:

MUL– Multiply (Rd = Rn * Rm)
MLA– Multiply-Accumulate (Rd = (Rn * Rm) + Ra)
UMULL– Unsigned Multiply Long (RdLo, RdHi = Rn * Rm)
UMLAL– Unsigned Multiply-Accumulate Long (RdLo, RdHi = (Rn * Rm) + RdLo, RdHi)
SMULL– Signed Multiply Long (RdLo, RdHi = Rn * Rm)
SMLAL– Signed Multiply-Accumulate Long (RdLo, RdHi = (Rn * Rm) + RdLo, RdHi)

6. Bit Manipulation Instructions (for ARMv6 and later)

CLZ– Count leading zeros in a register.
REV, REV16, REVSH– Byte reversal operations.

7. Saturation Instructions (for DSP extensions)

Used in DSP (Digital Signal Processing) applications:

SSAT– Signed saturation.
USAT– Unsigned saturation.

8. Miscellaneous Instructions

MOV– Move (Rd = Operand2)
MVN– Move NOT (Rd = ~Operand2)

These instructions allow efficient data manipulation, arithmetic computation, and logical operations in ARM architectures.