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## SMULLB (vectors)

Signed multiply long (bottom).

Multiply the corresponding even-numbered signed elements of the first and second source vectors, and place the results in the overlapping double-width elements of the destination vector. This instruction is unpredicated.

 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 0 1 0 0 0 1 0 1 size 0 Zm 0 1 1 1 0 0 Zn Zd

#### SVE2

SMULLB <Zd>.<T>, <Zn>.<Tb>, <Zm>.<Tb>

```if !HaveSVE2() then UNDEFINED;
if size == '00' then UNDEFINED;
integer esize = 8 << UInt(size);
integer n = UInt(Zn);
integer m = UInt(Zm);
integer d = UInt(Zd);```

### Assembler Symbols

 Is the name of the destination scalable vector register, encoded in the "Zd" field.
<T> Is the size specifier, encoded in size:
size <T>
00 RESERVED
01 H
10 S
11 D
 Is the name of the first source scalable vector register, encoded in the "Zn" field.
<Tb> Is the size specifier, encoded in size:
size <Tb>
00 RESERVED
01 B
10 H
11 S
 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) result;

for e = 0 to elements-1
integer element1 = SInt(Elem[operand1, 2*e + 0, esize DIV 2]);
integer element2 = SInt(Elem[operand2, 2*e + 0, esize DIV 2]);
integer res = element1 * element2;
Elem[result, e, esize] = res<esize-1:0>;

Z[d] = result;```