Does clzw access memory?
No. It reads integer register operands and writes rd only.
CLZW
RISC-V CLZW Instruction Details
Instruction ManualR-typeCount leading zero bits in word (RV64)
Instruction Syntax
clzw rd, rs1
Operand Breakdown
Destination rd: register receiving the operation result.
Source rs1: register holding the first operand.
Source rs2: register holding the second operand.
BZbbBit Manipulation
Related Search Terms
Instruction Behavior
clzw on RV64 examines only the low 32 bits of rs1 and returns a count from 0 to 32.
Quick Understanding & Search Notes
clzw on RV64 examines only the low 32 bits of rs1 and returns a count from 0 to 32.
These instructions are part of a B-extension subset and operate on XLEN-wide integer register values.
If the low 32 bits are zero, the result is 32, not XLEN.
Common Usage Scenarios
Bit Operations & Masks
Understand this scenario with real code like «clzw x10, x11 ; x10 = leading zeros in x11[31:0]».
Floating Point Basic
Understand this scenario with real code like «clzw x10, x11 ; x10 = leading zeros in x11[31:0]».
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
If the low 32 bits are zero, the result is 32, not XLEN.
FAQ
Does clzw interpret signed numbers?
These bit operations work on bit patterns directly; aside from the specified word-width selection, arithmetic signed magnitude is not used.