VFIRST.M

Vector Find First Set Mask Bit

VFIRST.M rd, vs2, vm

Finds the index of the first set bit in the mask.

Encoding

Binary Layout

010000

31:26

vm

25

vs2

24:20

10001010

19:12

rd

11:7

1010111

6:0

 

Format OPMVX

Opcode 0x4008A057

Extension V

Operands

• rd
  Dest (Index)
• vs2
  Src Mask

Example

VFIRST.M t0, v4, v0.t

Related

More in V

Reference

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

Description

Finds the index of the lowest-numbered active set bit in mask register vs2, writing the index to rd. Returns -1 if no bit is set.

Operation

rd = find_first_set(vs2 & vm);