Register Guide
RISC-V vlenb / vlenb Register: Vector Register Length in Bytes CSR
vlenb is the Vector Register Byte Length register (read-only CSR 0xC22), holding VLEN/8 — the byte width of a single vector register.
ABI name: vlenb; physical register: vlenb.
Save rule: Saved by software when context requires.
Read it through its psABI role first, then inspect how each instruction reads or writes it.
Physical Name vlenbABI Name vlenbSave Rule Saved by software when context requires
Role
Vector Register Length in Bytes CSR
Convention
Architectural state / CSR semantics
Remember This First
The calling convention listed for this entry is: Architectural state / CSR semantics.
RISC-V Vector ISA Reference
ABI register
vlenb is the Vector Register Byte Length register (read-only CSR 0xC22), holding VLEN/8 — the byte width of a single vector register.
Preserved across calls: Saved by software when context requires
RISC-V Unprivileged ISA Manual, V extensionWhen It Fits Best
- - Use it according to the documented role: Vector Register Length in Bytes CSR.
- - Consult the applicable ISA or ABI specification for concrete read, write, or execution semantics.
When Not To Use It This Way
- - Do not apply the integer temporary-register t* rules to this entry.
- - Do not infer behavior not defined by this page or the applicable specification from the ABI name.
What Happens Around A Call
1
The calling convention listed for this entry is: Architectural state / CSR semantics.
2
The save rule listed for this entry is: Saved by software when context requires.
Read The Documented Role
Examples explain the rule, not a complete program# vlenb / vlenb
# Vector Register Length in Bytes CSR
# Architectural state / CSR semantics