URHADD

Unsigned rounding halving add

This instruction adds corresponding unsigned integer values from the two source SIMD&FP registers, shifts each result right one bit, places the results into a vector, and writes the vector to the destination SIMD&FP register.

The results are rounded. For truncated results, see UHADD.

Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.

Three registers of the same type
(FEAT_AdvSIMD)

313029282726252423222120191817161514131211109876543210
0Q101110size1Rm000101RnRd
Uopcode

Encoding

URHADD <Vd>.<T>, <Vn>.<T>, <Vm>.<T>

Decode for this encoding

if !IsFeatureImplemented(FEAT_AdvSIMD) then EndOfDecode(Decode_UNDEF); end; if size == '11' then EndOfDecode(Decode_UNDEF); end; let d : integer{} = UInt(Rd); let n : integer{} = UInt(Rn); let m : integer{} = UInt(Rm); let esize : integer{} = 8 << UInt(size); let datasize : integer{} = 64 << UInt(Q); let elements : integer = datasize DIV esize;

Assembler Symbols

<Vd>

Is the name of the SIMD&FP destination register, encoded in the "Rd" field.

<T>

Is an arrangement specifier, encoded in (size :: Q):

size Q <T>
00 0 8B
00 1 16B
01 0 4H
01 1 8H
10 0 2S
10 1 4S
11 x RESERVED
<Vn>

Is the name of the first SIMD&FP source register, encoded in the "Rn" field.

<Vm>

Is the name of the second SIMD&FP source register, encoded in the "Rm" field.

Operation

AArch64_CheckFPAdvSIMDEnabled(); let operand1 : bits(datasize) = V{}(n); let operand2 : bits(datasize) = V{}(m); var result : bits(datasize); var element1 : integer; var element2 : integer; var sum : integer; for e = 0 to elements-1 do element1 = UInt(operand1[e*:esize]); element2 = UInt(operand2[e*:esize]); sum = (element1 + element2 + 1) >> 1; result[e*:esize] = sum[esize-1:0]; end; V{datasize}(d) = result;


2026-03_rel 2026-03-26 20:48:11

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