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## UXTAB16

Unsigned Extend and Add Byte 16 extracts two 8-bit values from a register, zero-extends them to 16 bits each, adds the results to two 16-bit values from another register, and writes the final results to the destination register. The instruction can specify a rotation by 0, 8, 16, or 24 bits before extracting the 8-bit values.

It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) .

### A1

 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 != 1111 0 1 1 0 1 1 0 0 != 1111 Rd rotate (0) (0) 0 1 1 1 Rm cond Rn

#### A1

UXTAB16{<c>}{<q>} {<Rd>,} <Rn>, <Rm> {, ROR #<amount>}

```if Rn == '1111' then SEE "UXTB16";
d = UInt(Rd);  n = UInt(Rn);  m = UInt(Rm);  rotation = UInt(rotate:'000');
if d == 15 || m == 15 then UNPREDICTABLE;```

### T1

 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 1 1 1 1 1 0 1 0 0 0 1 1 != 1111 1 1 1 1 Rd 1 (0) rotate Rm Rn

#### T1

UXTAB16{<c>}{<q>} {<Rd>,} <Rn>, <Rm> {, ROR #<amount>}

```if Rn == '1111' then SEE "UXTB16";
d = UInt(Rd);  n = UInt(Rn);  m = UInt(Rm);  rotation = UInt(rotate:'000');
if d == 15 || m == 15 then UNPREDICTABLE; // Armv8-A removes UNPREDICTABLE for R13```

For more information about the constrained unpredictable behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors.

### Assembler Symbols



 Is the general-purpose destination register, encoded in the "Rd" field.
 Is the first general-purpose source register, encoded in the "Rn" field.
 Is the second general-purpose source register, encoded in the "Rm" field.
<amount> Is the rotate amount, encoded in rotate:
rotate <amount>
00 (omitted)
01 8
10 16
11 24

### Operation

```if ConditionPassed() then
EncodingSpecificOperations();
rotated = ROR(R[m], rotation);
R[d]<15:0>  = R[n]<15:0> + ZeroExtend(rotated<7:0>, 16);
R[d]<31:16> = R[n]<31:16> + ZeroExtend(rotated<23:16>, 16);```

### Operational information

If CPSR.DIT is 1, this instruction has passed its condition execution check, and does not use R15 as either its source or destination:

• The execution time of this instruction is independent of:
• The values of the data supplied in any of its registers.
• The values of the NZCV flags.
• The response of this instruction to asynchronous exceptions does not vary based on:
• The values of the data supplied in any of its registers.
• The values of the NZCV flags.