Can VANDN.VV always use a v0.t mask?
It can use the vm mask operand shown in the syntax; omitting it gives the unmasked form.
VANDN.VV
RISC-V VANDN.VV Instruction Details
Instruction ManualR-typeVector bitwise AND-NOT: vd[i] = vs2[i] & ~vs1[i].
Instruction Syntax
vandn.vv vd, vs2, vs1, 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
vandn.vv inverts each bit of vs1[i] and ANDs it with the corresponding bits of vs2[i]: vd[i] = vs2[i] & ~vs1[i].
Quick Understanding & Search Notes
VANDN.VV is a Zvbb vector instruction for vector bitwise and-not. This page is checked against the official vector crypto extension and V-extension execution model.
vd[i] = vs2[i] & ~vs1[i]; note that vs1 is the inverted second source in the syntax.
It follows V-extension vl, vstart, vtype, and optional vm mask rules.
Common Usage Scenarios
Crypto & Security
Understand this scenario with real code like «vandn.vv vd, vs2, vs1».
Vector Acceleration
Understand this scenario with real code like «vandn.vv vd, vs2, vs1».
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
Note operand order: syntax is vd, vs2, vs1; the second source operand vs1 is inverted, while vs2 is not.
All SEW supported; subject to vstart and restart semantics.
FAQ
What determines the element width for VANDN.VV?
The current vtype SEW determines it, subject to any instruction-specific SEW restrictions in the extension.