Does cpopw access memory?
No. It reads integer register operands and writes rd only.
CPOPW
RISC-V CPOPW Instruction Details
Instruction ManualI-type (OP-IMM-32, RV64)Count set bits in word (RV64)
Instruction Syntax
cpopw rd, rs1
Operand Breakdown
This is a I-type (OP-IMM-32, RV64)-format instruction. Confirm operand positions based on the assembly syntax.
ZbbBit Manipulation
Related Search Terms
Instruction Behavior
cpopw on RV64 counts one bits only in the low 32 bits of rs1.
CPOPW Decode And Execute Animation
Starts with machine-code field decoding, then shows operand reads, instruction-specific execution, and ISA-visible state update.
rd
rs1
cpopw
,
Execution Context
t1(x6)
0x0000000000000014
31..20
19..15
14..12
11..7
6..0
011000000010
fixed imm[11:0]
00110
rs1
001
funct3
00101
rd
0011011
opcode
Execution Data Path
instruction
0x6023129B
opcode
0011011 -> OP-IMM-32
funct3
001 -> CPOPW
fixed imm[11:0]
011000000010 -> CPOPW selector
rd / rs1
t0(x5) / t1(x6)=0x00000014
fixed imm[11:0]
011000000010 selects CPOPW (not an arithmetic immediate)
population count
count 1-bits in rs1[31:0] -> 2
x5
t0(x5) = 0x0000000000000002
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: 0x6023129B
syntax : cpopw t0(x5), t1(x6)
result : t0(x5) = 0x0000000000000002
Architectural Result
t0(x5) = 0x0000000000000002
This animation shows ISA-visible decode and state changes, not any specific CPU pipeline, cache, prediction, or timing implementation.
Quick Understanding & Search Notes
cpopw on RV64 counts one bits only in the low 32 bits of rs1.
CPOPW is an RV64 Zbb OP-IMM-32 instruction and counts only the low 32 bits of rs1.
The result range is 0..32; upper bits do not participate.
Common Usage Scenarios
Bit Operations & Masks
Understand this scenario with real code like «cpopw x10, x11 ; x10 = number of 1-bits in x11[31:0]».
Pre-Use Checklist
Syntax Check
- Confirm the current instruction format is I-type (OP-IMM-32, RV64).
- 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..32; upper bits do not participate.
FAQ
Does cpopw interpret signed numbers?
These bit operations work on bit patterns directly; aside from the specified word-width selection, arithmetic signed magnitude is not used.