RISC-V VCPOP.V Instruction Details

Instruction ManualR-type

Vector population count: count set bits (1s) in each element

Instruction Syntax

vcpop.v vd, vs2, vm

Operand Breakdown

Destination rd: register receiving the operation result.

Source rs1: register holding the first operand.

Source rs2: register holding the second operand.

ZvbbVector Bit Manipulation

Related Search Terms

vcpop.v instruction RISC-V vcpop.v vcpop.v syntax vcpop.v encoding Zvbb vector population count

Instruction Behavior

vcpop.v is the Zvbb vector population count instruction. Counts the number of set bits (Hamming weight) in each element. Supports all SEW.

Quick Understanding & Search Notes

VCPOP.V is a Zvbb vector instruction for vector population count. This page is checked against the official vector crypto extension and V-extension execution model.

Each element returns the count of set bits, not a bit position.

It follows V-extension vl, vstart, vtype, and optional vm mask rules.

RISC-V Unprivileged ISA Manual: Vector cryptography extensions 1.0 RISC-V Unprivileged ISA Manual: V standard vector extension

Common Usage Scenarios

Crypto & Security

Understand this scenario with real code like «vcpop.v vd, vs2».

Vector Acceleration

Understand this scenario with real code like «vcpop.v vd, vs2».

Pre-Use Checklist

Syntax Check

Confirm the current instruction format is R-type.
Confirm the operand order matches the example.

Semantic Check

Ensure the destination register usage is compatible with the calling convention.
Confirm this is not the lower-level form of a pseudo-instruction expansion.

Pitfalls / Common Confusions

Result is count (0..SEW), not a bit position.

FAQ

Can VCPOP.V always use a v0.t mask?

It can use the vm mask operand shown in the syntax; omitting it gives the unmasked form.

What determines the element width for VCPOP.V?

The current vtype SEW determines it, subject to any instruction-specific SEW restrictions in the extension.