FDOT (2-way, multiple and indexed vector, FP8 to FP16)

Multi-vector 8-bit floating-point dot-product by indexed element to half-precision

The instruction computes the fused sum-of-products of a group of two 8-bit floating-point values held in the corresponding 16-bit elements of the two or four first source vectors and the indexed 16-bit element of the second source vector. The half-precision sum-of-products are scaled by 2^{-UInt(FPMR.LSCALE[3:0])}, before being destructively added without intermediate rounding to the corresponding half-precision elements of the ZA single-vector groups. The 8-bit floating-point encoding format for the elements of the first source vector and the second source vector is selected by FPMR.F8S1 and FPMR.F8S2 respectively.

The 8-bit floating-point pairs within the second source vector are specified using an immediate index which selects the same pair position within each 128-bit vector segment.

The single-vector group within each half of or each quarter of the ZA array is selected by the sum of the vector select register and offset , modulo half or quarter the number of ZA array vectors.

The vector group symbol, VGx2 or VGx4, indicates that the ZA operand consists of two or four ZA single-vector groups respectively. The vector group symbol is preferred for disassembly, but optional in assembler source code.

This instruction is unpredicated.

It has encodings from 2 classes: Two ZA single-vectors and Four ZA single-vectors

Two ZA single-vectors
(FEAT_SME_F8F16)

Decode for this encoding

if !IsFeatureImplemented(FEAT_SME_F8F16) then EndOfDecode(Decode_UNDEF); constant integer v = UInt('010':Rv); constant integer n = UInt(Zn:'0'); constant integer m = UInt('0':Zm); constant integer offset = UInt(off3); constant integer index = UInt(i3h:i3l); constant integer nreg = 2;

Four ZA single-vectors
(FEAT_SME_F8F16)

Decode for this encoding

if !IsFeatureImplemented(FEAT_SME_F8F16) then EndOfDecode(Decode_UNDEF); constant integer v = UInt('010':Rv); constant integer n = UInt(Zn:'00'); constant integer m = UInt('0':Zm); constant integer offset = UInt(off3); constant integer index = UInt(i3h:i3l); constant integer nreg = 4;