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SDOT (vectors)

Signed dot product.

The signed integer partial dot product instruction delimits the source vectors into quadtuplets of four 8-bit or 16-bit signed integer elements. Within each quadtuplet the elements in the first source vector are multiplied by the corresponding elements in the second source vector and the resulting widened products are summed and added to the 32-bit or 64-bit element of the accumulator and destination vector which aligns with the quadtuplet in the first source vector.

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01000100size0Zm000000ZnZda
if !HaveSVE() then UNDEFINED;
if size == '0x' then UNDEFINED;
integer esize = 8 << UInt(size);
integer n = UInt(Zn);
integer m = UInt(Zm);
integer da = UInt(Zda);

Assembler Symbols

<Zda>

Is the name of the third source and destination scalable vector register, encoded in the "Zda" field.

<T> Is the size specifier, encoded in size<0>:
size<0> <T>
0 S
1 D
<Zn>

Is the name of the first source scalable vector register, encoded in the "Zn" field.

<Tb> Is the size specifier, encoded in size<0>:
size<0> <Tb>
0 B
1 H
<Zm>

Is the name of the second source scalable vector register, encoded in the "Zm" field.

Operation

CheckSVEEnabled();
integer elements = VL DIV esize;
bits(VL) operand1 = Z[n];
bits(VL) operand2 = Z[m];
bits(VL) operand3 = Z[da];
bits(VL) result;

for e = 0 to elements-1
    bits(esize) res = Elem[operand3, e, esize];
    for i = 0 to 3
        integer element1 = SInt(Elem[operand1, 4 * e + i, esize DIV 4]);
        integer element2 = SInt(Elem[operand2, 4 * e + i, esize DIV 4]);
        res = res + element1 * element2;
    Elem[result, e, esize] = res;

Z[da] = result;

Operational information

This instruction might be immediately preceded in program order by a MOVPRFX instruction that conforms to all of the following requirements, otherwise the behavior of either or both instructions is unpredictable:

  • The MOVPRFX instruction must specify the same destination register as this instruction.
  • The destination register must not refer to architectural register state referenced by any other source operand register of this instruction.
The MOVPRFX instructions that can be used with this instruction are as follows:
  • An unpredicated MOVPRFX instruction.