Does cpop access memory?
No. It reads integer register operands and writes rd only.
CPOP
RISC-V CPOP Instruction Details
Instruction ManualI-type (OP-IMM)Count set bits (population count)
Instruction Syntax
cpop rd, rs1
Operand Breakdown
This is a I-type (OP-IMM)-format instruction. Confirm operand positions based on the assembly syntax.
ZbbBit ManipulationInteger Operation
Related Search Terms
Instruction Behavior
cpop returns the number of one bits in rs1.
CPOP Decode And Execute Animation
Starts with machine-code field decoding, then shows operand reads, instruction-specific execution, and ISA-visible state update.
rd
rs1
cpop
,
Execution Context
t1(x6)
0x00000014
31..20
19..15
14..12
11..7
6..0
011000000010
fixed imm[11:0]
00110
rs1
001
funct3
00101
rd
0010011
opcode
Execution Data Path
instruction
0x60231293
opcode
0010011 -> OP-IMM
funct3
001 -> CPOP
fixed imm[11:0]
011000000010 -> CPOP selector
rd / rs1
t0(x5) / t1(x6)=0x00000014
fixed imm[11:0]
011000000010 selects CPOP (not an arithmetic immediate)
population count
count 1-bits in rs1[31:0] -> 2
x5
t0(x5) = 0x00000002
Current Step
Concept Step: receive the 32-bit instruction encoding
The machine code is split by the current instruction format; the animation starts from encoding/decode.
encoding: 0x60231293
syntax : cpop t0(x5), t1(x6)
result : t0(x5) = 0x00000002
Architectural Result
t0(x5) = 0x00000002
This animation shows ISA-visible decode and state changes, not any specific CPU pipeline, cache, prediction, or timing implementation.
Quick Understanding & Search Notes
cpop returns the number of one bits in rs1.
CPOP is an OP-IMM instruction in the Zbb basic bit-manipulation extension and counts the XLEN bits of rs1.
The result range is 0..XLEN.
Common Usage Scenarios
Bit Operations & Masks
Understand this scenario with real code like «cpop x10, x11 ; x10 = number of 1-bits in x11».
Pre-Use Checklist
Syntax Check
- Confirm the current instruction format is I-type (OP-IMM).
- 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
The result range is 0..XLEN.
FAQ
Does cpop interpret signed numbers?
These bit operations work on bit patterns directly; aside from the specified word-width selection, arithmetic signed magnitude is not used.