Are VRGATHEREI16.VV indices byte offsets?
No. VRGATHER indices select source-vector elements; byte offsets belong to indexed load/store instructions.
VRGATHEREI16.VV
RISC-V VRGATHEREI16.VV Instruction Details
Instruction ManualR-typeGather source-vector elements using 16-bit index elements.
Instruction Syntax
vrgatherei16.vv vd, vs2, vs1, vm
Operand Breakdown
Destination rd: register receiving the operation result.
Source rs1: register holding the first operand.
Source rs2: register holding the second operand.
VVector PermutationGather
Instruction Behavior
VRGATHEREI16.VV uses indices from vs1 to select elements from vs2 into vd; an index outside VLMAX produces a zero result element.
Quick Understanding & Search Notes
VRGATHEREI16.VV handles index-based rearrangement of vector elements, with source data coming from vs2.
The index selects an element of vs2; it is not a memory address.
An index outside VLMAX writes zero to the destination element.
VRGATHEREI16.VV uses fixed 16-bit index elements, allowing smaller index widths with larger data SEW.
Common Usage Scenarios
Large Table Lookup
Understand this scenario with real code like «vrgatherei16.vv v8, v12, v4, v0.t».
Sparse Data
Understand this scenario with real code like «vrgatherei16.vv v8, v12, v4, v0.t».
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
Index EEW fixed 16-bit independent of data SEW
OOB returns 0