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## FVDOT

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

The instruction computes the fused sum-of-products of each vertical pair of half-precision floating-point values in the corresponding elements of the two first source vectors with the pair of half-precision floating-point values in the indexed 32-bit group of the corresponding 128-bit segment of the second source vector, without intermediate rounding. The single-precision sum-of-products results are destructively added to the corresponding single-precision elements of the two 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 vector numbers forming the single-vector group within each half of the ZA array are selected by the sum of the vector select register and immediate offset, modulo half the number of ZA array vectors.

The vector group symbol VGx2 indicates that the ZA operand consists of two ZA single-vector groups. 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.

### SME2
(FEAT_SME2)

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
1 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 1 | Zm | 0 | Rv | 0 | i2 | Zn | 0 | 0 | 1 | off3

####

FVDOT ZA.S[<Wv>, <offs>{, VGx2}], { <Zn1>.H-<Zn2>.H }, <Zm>.H[<index>]

if !HaveSME2() then UNDEFINED; integer v = UInt('010':Rv); integer n = UInt(Zn:'0'); integer m = UInt('0':Zm); integer offset = UInt(off3); integer index = UInt(i2);

### Assembler Symbols

<Wv> | Is the 32-bit name of the vector select register W8-W11, encoded in the "Rv" field.

<offs> | Is the vector select offset, in the range 0 to 7, encoded in the "off3" field.

<Zn1> | Is the name of the first scalable vector register of a multi-vector sequence, encoded as "Zn" times 2.

<Zn2> | Is the name of the second scalable vector register of a multi-vector sequence, encoded as "Zn" times 2 plus 1.

<Zm> | Is the name of the second source scalable vector register Z0-Z15, encoded in the "Zm" field.

<index> | Is the immediate index of a group of two 16-bit elements within each 128-bit vector segment, in the range 0 to 3, encoded in the "i2" field.

### Operation

CheckStreamingSVEAndZAEnabled(); constant integer VL = CurrentVL; constant integer elements = VL DIV 32; integer vectors = VL DIV 8; integer vstride = vectors DIV 2; integer eltspersegment = 128 DIV 32; bits(32) vbase = X[v, 32]; integer vec = (UInt(vbase) + offset) MOD vstride; bits(VL) result; for r = 0 to 1 bits(VL) operand1a = Z[n, VL]; bits(VL) operand1b = Z[n+1, VL]; bits(VL) operand2 = Z[m, VL]; bits(VL) operand3 = ZAvector[vec, VL]; for e = 0 to elements-1 integer segmentbase = e - (e MOD eltspersegment); integer s = segmentbase + index; bits(16) elt1_a = Elem[operand1a, 2 * e + r, 16]; bits(16) elt1_b = Elem[operand1b, 2 * e + r, 16]; bits(16) elt2_a = Elem[operand2, 2 * s + 0, 16]; bits(16) elt2_b = Elem[operand2, 2 * s + 1, 16]; bits(32) sum = Elem[operand3, e, 32]; sum = FPDotAdd_ZA(sum, elt1_a, elt1_b, elt2_a, elt2_b, FPCR[]); Elem[result, e, 32] = sum; ZAvector[vec, VL] = result; vec = vec + vstride;

Base Instructions | SIMD&FP Instructions | SVE Instructions | SME Instructions | Index by Encoding | Shared Pseudocode | Proprietary Notice

Internal version only: isa v33.64, AdvSIMD v29.12, pseudocode v2023-06_rel, sve v2023-06_rel ; Build timestamp: 2023-07-04T19:42

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