FDOT (2-way, indexed, FP8 to FP16)
8-bit floating-point indexed dot product to half-precision
This instruction computes the fused sum-of-products of a group of two 8-bit floating-point values held in each 16-bit element of the first source vector and a group of two 8-bit floating-point values in an 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 destination vector.
The 8-bit floating-point groups within the second source vector are specified using an immediate index which selects the same group position within each 128-bit vector segment. 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.
This instruction is unpredicated.
Green
False
True
0
1
1
0
0
1
0
0
0
0
1
0
1
0
0
1
FDOT <Zda>.H, <Zn>.B, <Zm>.B[<imm>]
if !HaveSVE2FP8DOT2() then UNDEFINED;
constant integer n = UInt(Zn);
constant integer m = UInt(Zm);
constant integer da = UInt(Zda);
constant integer index = UInt(i3h:i3l);
<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 Z0-Z7, encoded in the "Zm" field.
<imm>
Is the immediate index of a group of two 8-bit elements within each 128-bit vector segment, in the range 0 to 7, encoded in the "i3h:i3l" fields.
CheckFPMREnabled();
if IsFeatureImplemented(FEAT_FP8DOT2) then
CheckSVEEnabled();
else
CheckStreamingSVEEnabled();
constant integer VL = CurrentVL;
constant integer elements = VL DIV 16;
constant integer eltspersegment = 128 DIV 16;
constant bits(VL) operand1 = Z[n, VL];
constant bits(VL) operand2 = Z[m, VL];
constant bits(VL) operand3 = Z[da, VL];
bits(VL) result;
for e = 0 to elements-1
constant integer segmentbase = e - (e MOD eltspersegment);
constant integer s = segmentbase + index;
constant bits(16) op1 = Elem[operand1, e, 16];
constant bits(16) op2 = Elem[operand2, s, 16];
bits(16) sum = Elem[operand3, e, 16];
sum = FP8DotAddFP(sum, op1, op2, FPCR, FPMR);
Elem[result, e, 16] = sum;
Z[da, VL] = result;