VIOTA.M

Vector Iota

VIOTA.M vd, vs2, vm

Writes the index of the active element to the destination. Useful for parallel prefix sums.

Encoding

Binary Layout

010100

31:26

vm

25

vs2

24:20

10000010

19:12

vd

11:7

1010111

6:0

 

Format OPMVV

Opcode 0x50082057

Extension V

Operands

• vd
  Destination vector register
• vs2
  Mask Src

Example

VIOTA.M v1, v4, v0.t

Related

More in V

Reference

View in RISC-V Unprivileged ISA Specification ↗ RISC-V ISA Manual

Description

Writes to each element of vd the sum of set mask bits in vs2 at positions less than the current element index.

Operation

count = 0; foreach(i < vl): if vm[i]: vd[i] = count++;