* 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:

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.