histseg

Histogram Segment (SVE2)

HISTSEG <Zd>.B, <Zn>.B, <Zm>.B

Counts matching elements in segments of a vector.

Pseudocode Operation

No pseudocode available.

Encoding

Binary Layout

01000101

31:24

size

23:22

20:16

101000

15:10

9:5

4:0

Format SVE2 Histogram

Opcode 0x4520A000

Extension SVE2

Operands

Zd
Dest
Zn
Input
Zm
Reference

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x4520A000	HISTSEG <Zd>.B, <Zn>.B, <Zm>.B		A64		01000101 \| size \| 1 \| Zm \| 101000 \| Zn \| Zd

Description

This instruction compares each 8-bit byte element of the first source vector with all of the elements in the corresponding 128-bit segment of the second source vector and places the count of matching elements in the corresponding element of the destination vector. This instruction is unpredicated. This instruction is illegal when executed in Streaming SVE mode, unless FEAT_SME_FA64 is implemented and enabled.

Operation

CheckNonStreamingSVEEnabled();
constant integer VL = CurrentVL;
constant integer segments = VL DIV 128;
constant integer eltspersegment = 128 DIV esize;
bits(VL) operand1 = Z[n, VL];
bits(VL) operand2 = Z[m, VL];
bits(VL) result;

for b = 0 to segments-1
    for s = 0 to eltspersegment-1
        integer count = 0;
        integer e = eltspersegment * b + s;
        bits(esize) element1 = Elem[operand1, e, esize];
        for i = 0 to eltspersegment-1
            integer e2 = eltspersegment * b + i;
            bits(esize) element2 = Elem[operand2, e2, esize];
            if element1 == element2 then
                count = count + 1;
        Elem[result, e, esize] = count<esize-1:0>;

Z[d, VL] = result;