Can VBREV.V always use a v0.t mask?
It can use the vm mask operand shown in the syntax; omitting it gives the unmasked form.
VBREV.V
RISC-V VBREV.V Instruction Details
Instruction ManualR-typeVector bit-reverse whole element: reverse all bits within each SEW-width element
Instruction Syntax
vbrev.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
Instruction Behavior
vbrev.v is the Zvbb vector full bit-reverse instruction. Reverses all bits within each SEW-width element: bit[0]↔bit[SEW-1], bit[1]↔bit[SEW-2], etc. Unlike vbrev8.v (byte-internal reverse), this operates across the entire SEW width.
Quick Understanding & Search Notes
VBREV.V is a Zvbb vector instruction for vector reverse bits in elements. This page is checked against the official vector crypto extension and V-extension execution model.
Reverses all bits within each SEW-width element.
It follows V-extension vl, vstart, vtype, and optional vm mask rules.
Common Usage Scenarios
Crypto & Security
Understand this scenario with real code like «vbrev.v vd, vs2».
Vector Acceleration
Understand this scenario with real code like «vbrev.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
Full bit reversal across entire SEW width, not per-byte.
Distinct from vbrev8.v (byte-internal reverse); do not confuse.
FAQ
What determines the element width for VBREV.V?
The current vtype SEW determines it, subject to any instruction-specific SEW restrictions in the extension.