FDOT (8-bit floating-point to single-precision, vector)

8-bit floating-point dot product to single-precision (vector)

This instruction calculates the fused sum-of-products of a group of four 8-bit floating-point values held in each 32-bit element of the first and second source vectors. The single-precision sum-of-products are scaled by 2-UInt(FPMR.LSCALE), before being destructively added without intermediate rounding to the corresponding single-precision elements of the destination vector.

The 8-bit floating-point encoding format for the elements of the first source vector is selected by FPMR.F8S1. The 8-bit floating-point encoding format for the elements of the second source vector is selected by FPMR.F8S2.

Advanced SIMD
(FEAT_FP8DOT4)

313029282726252423222120191817161514131211109876543210
0Q001110000Rm111111RnRd
Usizeopcode

Encoding

FDOT <Vd>.<Ta>, <Vn>.<Tb>, <Vm>.<Tb>

Decode for this encoding

if !IsFeatureImplemented(FEAT_FP8DOT4) then EndOfDecode(Decode_UNDEF); end; let d : integer{} = UInt(Rd); let n : integer{} = UInt(Rn); let m : integer{} = UInt(Rm); let datasize : integer{} = if Q == '1' then 128 else 64; let esize : integer{} = 32; let elements : integer = datasize DIV esize;

Assembler Symbols

<Vd>

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

<Ta>

Is an arrangement specifier, encoded in Q:

Q <Ta>
0 2S
1 4S
<Vn>

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

<Tb>

Is an arrangement specifier, encoded in Q:

Q <Tb>
0 8B
1 16B
<Vm>

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

Operation

CheckFPMREnabled(); AArch64_CheckFPAdvSIMDEnabled(); let operand1 : bits(datasize) = V{}(n); let operand2 : bits(datasize) = V{}(m); let operand3 : bits(datasize) = V{}(d); var result : bits(datasize); for e = 0 to elements-1 do let op1 : bits(esize) = operand1[e*:esize]; let op2 : bits(esize) = operand2[e*:esize]; var sum : bits(esize) = operand3[e*:esize]; sum = FP8DotAddFP{esize, esize}(sum, op1, op2, FPCR(), FPMR()); result[e*:esize] = sum; end; V{datasize}(d) = result;


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

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