How does VLM.V handle masking?
It has no ordinary v0 execution mask; if a mask operand appears in the syntax, that operand is data, not an extra execution mask.
VLM.V
RISC-V VLM.V Instruction Details
Instruction ManualR-typeLoad ceil(vl/8) contiguous bytes from memory and place their bits into the destination vector mask.
Instruction Syntax
vlm.v vd, (rs1)
Operand Breakdown
Destination rd: register receiving the operation result.
Source rs1: register holding the first operand.
Source rs2: register holding the second operand.
VVector LoadMask Operations
Related Search Terms
Instruction Behavior
VLM.V is the RISC-V V vector mask-load instruction. It reads the compact mask byte sequence, ceil(vl/8) bytes, and maps those bits into the destination mask register. It restores or transfers RVV mask values rather than loading ordinary SEW-sized data elements.
Quick Understanding & Search Notes
VLM.V loads a compact stream of mask bits, not an ordinary integer vector; the memory footprint is determined by vl bits.
The access size is ceil(vl/8) bytes, addressed from x[rs1].
Mask element layout follows the RVV mask-register layout, and element validity is determined by the current vl.
This instruction is an unmasked form with no extra v0 execution mask; destination element coverage is defined by the instruction and current vl.
Common Usage Scenarios
Mask Save/Restore
Understand this scenario with real code like «vlm.v v0, (a0) # load full VLEN-bit mask».
Context Switch
Understand this scenario with real code like «vlm.v v0, (a0) # load full VLEN-bit mask».
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
Effective length is ceil(vl/8) bytes, not VLEN bytes.
The destination is treated as a mask value and is tail-agnostic.