Does UNZIP access memory?
No. It only rearranges bit fields or performs register lookup within integer registers.
UNZIP
RISC-V UNZIP Instruction Details
Instruction ManualI-typeRV32 bit deinterleave (Zbkb), RV32-only.
Instruction Syntax
unzip rd, rs1
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.
ZbkbBit Manipulation
Instruction Behavior
UNZIP (Zbkb, RV32-only) gathers even-numbered bits of rs1 into the low 16 bits of rd and odd-numbered bits into the high 16 bits: for i=0..15, rd[i]=rs1[2*i] and rd[i+16]=rs1[2*i+1]. It is the inverse of ZIP.
Quick Understanding & Search Notes
UNZIP is a Zbkb cryptographic bit-manipulation instruction; this page follows the official B-extension operation.
The official encoding and semantics are RV32-only.
These instructions rearrange bit/byte fields and do not access memory.
Common Usage Scenarios
Crypto & Security
Understand this scenario with real code like «unzip a0, a1».
Logical Operations
Understand this scenario with real code like «unzip a0, a1».
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
UNZIP is defined only on RV32; there is no RV64 form.
It deinterleaves bits, not bytes or halfwords.
This instruction is RV32-only; there is no RV64 form.
FAQ
Which extension contains UNZIP?
It belongs to the Zbkb cryptographic bit-manipulation extension.