Check vl first
The current vl determines the number of body elements. Typical code executes vsetvli, vsetivli, or vsetvl before this instruction.
VSHA2CL.VV
RISC-V VSHA2CL.VV Instruction Details
Instruction ManualR-typeVector two SHA-2 compression rounds using state groups and message-schedule constants; Zvknha uses SEW=32 and Zvknhb supports SEW=32/64.
Instruction Syntax
vsha2cl.vv vd, vs2, vs1
Operand Breakdown
vd: destination vector register group.
vs2/vs1 or scalar source: selected by suffixes such as .vv, .vx, .vi, or .vf.
vm: when present, vm=0 uses v0 as the execution mask and vm=1 is unmasked.
ZvknhaZvknhbVector CryptoSHA-256
Instruction Behavior
VSHA2CL.VV is a vector SHA-2 element-group instruction. It performs two compression rounds using current state in vd and vs2 plus message-schedule/constant data in vs1; vd is both input and output. Under Zvknha SEW must be 32; under Zvknhb SEW may be 32 or 64.
Quick Understanding & Search Notes
VSHA2CL.VV is a vector SHA-2 element-group instruction, not an ordinary per-element arithmetic operation and not a v0.t-masked operation.
SEW=32 corresponds to SHA-256; SEW=64 corresponds to SHA-512 and requires Zvknhb.
Register-group overlap restrictions are part of encoding legality.
Vector Execution Context
When reading VSHA2CL.VV, do not stop at the mnemonic. Official V-extension semantics also depend on the current vl, vtype, and mask state. .vv: two vector sources participate element by element.
Then check vtype
The current vtype supplies SEW, LMUL, tail policy, and mask policy; these affect element width, register-group size, and inactive/tail destination elements.
Then check vm/v0
For ordinary vector instructions with vm, vm=0 uses v0 as the execution mask and vm=1 is unmasked. A few forms such as VMERGE use v0 as data-selection input.
Common Usage Scenarios
Crypto & Security
Understand this scenario with real code like «vsha2cl.vv vd, vs2, vs1».
Vector Acceleration
Understand this scenario with real code like «vsha2cl.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
There is no vm operand; this element-group crypto instruction is unmasked.
The vd register group must not overlap vs1 or vs2.
SHA-2 uses EGS=4; vl and vstart must be aligned to element groups.
Software must handle SHA-2 big-endian message/final-hash byte ordering as required by the algorithm.
FAQ
Does VSHA2CL.VV support vm masking?
No. The official syntax has no vm operand.
How is SEW selected for VSHA2CL.VV?
It comes from current vtype, but must satisfy the Zvknha/Zvknhb SEW restrictions.