UDOT (2-way, vectors)

Unsigned integer dot product (two-way)

This instruction calculates the dot product of a pair of unsigned 16-bit integer values held in each 32-bit element of the first source vector multiplied by a pair of unsigned 16-bit integer values in the corresponding 32-bit element of the second source vector, and then destructively adds the widened dot product to the corresponding 32-bit element of the destination vector.

This instruction is unpredicated.

16-bit to 32-bit
(FEAT_SME2 || FEAT_SVE2p1)

313029282726252423222120191817161514131211109876543210
01000100000Zm110011ZnZda
U

Encoding

UDOT <Zda>.S, <Zn>.H, <Zm>.H

Decode for this encoding

if !IsFeatureImplemented(FEAT_SME2) && !IsFeatureImplemented(FEAT_SVE2p1) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 32; let n : integer = UInt(Zn); let m : integer = UInt(Zm); let da : integer = UInt(Zda);

Assembler Symbols

<Zda>

Is the name of the third source and destination scalable vector register, encoded in the "Zda" field.

<Zn>

Is the name of the first source scalable vector register, encoded in the "Zn" field.

<Zm>

Is the name of the second source scalable vector register, encoded in the "Zm" field.

Operation

CheckSVEEnabled(); let VL : integer{} = CurrentVL(); let elements : integer = VL DIV esize; let operand1 : bits(VL) = Z{}(n); let operand2 : bits(VL) = Z{}(m); let operand3 : bits(VL) = Z{}(da); var result : bits(VL); for e = 0 to elements-1 do var res : bits(esize) = operand3[e*:esize]; for i = 0 to 1 do let element1 : integer = UInt(operand1[(2 * e + i)*:(esize DIV 2)]); let element2 : integer = UInt(operand2[(2 * e + i)*:(esize DIV 2)]); res = res + element1 * element2; end; result[e*:esize] = res; end; Z{VL}(da) = result;

Operational information

This instruction is a data-independent-time instruction as described in About PSTATE.DIT.

This instruction might be immediately preceded in program order by a MOVPRFX instruction. The MOVPRFX must conform to all of the following requirements, otherwise the behavior of the MOVPRFX and this instruction is CONSTRAINED UNPREDICTABLE:


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

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