Does SLLI.UW access memory?
No. It only reads and writes integer registers; any memory access must be performed by a separate load or store instruction.
SLLI.UW
RISC-V SLLI.UW Instruction Details
Instruction ManualI-typeShift left unsigned word by immediate (RV64)
Instruction Syntax
slli.uw rd, rs1, shamt
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.
BZbaAddress Generation
Instruction Behavior
Zero-extends lower 32 bits of rs1, shifts left by shamt (0-63). Equivalent to add.uw followed by slli. Part of Zba.
Quick Understanding & Search Notes
SLLI.UW is a B/Zba instruction for zero-extend low word then shift left immediate. This page is checked against the official B extension semantics, with emphasis on XLEN, W suffixes, .uw suffixes, and bitwise or rotate boundaries.
It extracts and zero-extends the low 32 bits of rs1, then shifts left by the immediate.
It is an RV64 Zba instruction useful for unsigned 32-bit index expansion; do not treat it as sign-extension followed by a shift.
Common Usage Scenarios
Shift & Rotate
Understand this scenario with real code like «slli.uw x10, x11, 4 ; x10 = zero_ext(x11[31:0]) << 4».
Type Conversion
Understand this scenario with real code like «slli.uw x10, x11, 4 ; x10 = zero_ext(x11[31:0]) << 4».
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
RV64 only
shamt range 0-63
FAQ
What is the result width of SLLI.UW?
Except that W-suffixed forms produce a 32-bit result then sign-extend and .uw forms first extract a 32-bit unsigned operand, the result is written to rd at XLEN width.