Is VSM4K.VI an element-wise masked operation?
No. It is an element-group crypto instruction and the official syntax has no vm.
VSM4K.VI
RISC-V VSM4K.VI Instruction Details
Instruction ManualI-typeVector SM4 round-key expansion selected by uimm; executes as an unmasked element-group crypto instruction.
Instruction Syntax
vsm4k.vi vd, vs2, uimm
Operand Breakdown
Destination rd: general-purpose register receiving the result.
Source rs1: register holding the first operand.
Immediate imm: 12-bit signed value, sign-extended before operation with rs1.
ZvksedVector CryptoSM4
Instruction Behavior
VSM4K.VI is a vector SM4 round-key expansion selected by uimm instruction. SM4 forms use SEW=32, EGW=128, and EGS=4.
Quick Understanding & Search Notes
VSM4K.VI is an SM4 vector crypto instruction executed over element groups, not an ordinary independent per-element integer operation.
SM4 uses 128-bit element groups; the .vs form takes one scalar element group from vs2.
The official syntax has no vm operand, so v0.t masking is not added.
Common Usage Scenarios
Crypto & Security
Understand this scenario with real code like «vsm4k.vi vd, vs2, uimm».
Vector Acceleration
Understand this scenario with real code like «vsm4k.vi vd, vs2, uimm».
Pre-Use Checklist
Syntax Check
- Confirm the current instruction format is I-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.
SEW must be 32, and vl/vstart must be multiples of EGS=4.
Watch vd input/output use and the official register-group overlap restrictions.
FAQ
What vtype restriction matters for VSM4K.VI?
SEW must be 32 and LMUL*VLEN must cover a 128-bit element group.