FDOT (2-way, multiple and indexed vector, FP16 to FP32)

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

The instruction computes the fused sum-of-products of a pair of half-precision floating-point values held in the corresponding 32-bit elements of the two or four first source vectors and the indexed 32-bit element of the second source vector, without intermediate rounding. The single-precision sum-of-products are destructively added to the corresponding single-precision elements of the ZA single-vector groups.

The half-precision 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 element index range is from 0 to 3.

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 follows SME ZA-targeting floating-point behaviors.

This instruction is unpredicated.

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

Two ZA single-vectors
(FEAT_SME2)

Decode for this encoding

if !IsFeatureImplemented(FEAT_SME2) 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(i2); constant integer nreg = 2;

Four ZA single-vectors
(FEAT_SME2)

Decode for this encoding

if !IsFeatureImplemented(FEAT_SME2) 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(i2); constant integer nreg = 4;