uxtab

Unsigned Extend and Add Byte

UXTAB<c> <Rd>, <Rn>, <Rm> {, <rotation>}

Zero-extends a byte and adds to Rn.

Details

Zero-extends the least significant byte of Rm (optionally rotated), adds it to Rn, and writes the result to Rd. This is an A32 instruction that operates on general-purpose registers and does not affect the condition flags. The rotation parameter is optional (ROR by 0, 8, 16, or 24 bits before zero-extension).

Pseudocode Operation

rotated ← ROR(Rm, rotation)
byte_value ← rotated[7:0]
zero_extended ← ZeroExtend(byte_value, 32)
Rd ← Rn + zero_extended

Example

UXTAB r0, r1, r2

Encoding

Binary Layout
cond
01101
1
10
Rn
Rd
rotate
0
0
0111
Rm
 
Format Data Proc
Opcode 0x06E00070
Extension A32 (DSP)

Operands

  • Rd
    Destination general-purpose register
  • Rn
    Accumulator
  • Rm
    Second source / offset general-purpose register

Reference (Arm AArch32 ISA)

Instruction Forms

Encoding Instruction ISA Bit pattern
0x06E00070 UXTAB{<c>}{<q>} {<Rd>,} <Rn>, <Rm> {, ROR #<amount>} A32 cond | 01101 | 1 | 10 | Rn | Rd | rotate | 0 | 0 | 0111 | Rm
0xFA50F080 UXTAB{<c>}{<q>} {<Rd>,} <Rn>, <Rm> {, ROR #<amount>} T32 111110100 | 10 | 1 | Rn | 1111 | Rd | 1 | 0 | rotate | Rm

Description

Unsigned Extend and Add Byte extracts an 8-bit value from a register, zero-extends it to 32 bits, adds the result to the value in another register, and writes the final result to the destination register. The instruction can specify a rotation by 0, 8, 16, or 24 bits before extracting the 8-bit value.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    rotated = ROR(R[m], rotation);
    R[d] = R[n] + ZeroExtend(rotated<7:0>, 32);