Does bexti access memory?
No. It reads integer register operands and writes rd only.
BEXTI
RISC-V BEXTI Instruction Details
Instruction ManualI-typeExtract single bit by immediate index
Instruction Syntax
bexti rd, rs1, uimm
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.
BZbsBit ManipulationSingle-Bit Operation
Related Search Terms
Instruction Encoding
31..20
imm[11:0]
19..15
rs1
14..12
funct3
11..7
rd
6..0
opcode
BEXTI uses opcode 0010011 (0x13), funct3 101, funct7 0100100. The rs1 field selects the source register, the 12-bit immediate provides the second operand, and rd selects the destination.
Format: I-type
opcode: 0010011 (0x13)
funct3: 101 (0x5)
funct7: 0100100 (0x24)
Instruction Behavior
bexti is a Zbs single-bit extract instruction. The bit index comes from the immediate field.
Quick Understanding & Search Notes
bexti is a Zbs single-bit extract instruction. The bit index comes from the immediate field.
These instructions are part of a B-extension subset and operate on XLEN-wide integer register values.
The immediate field width depends on XLEN; RV32 encodes 0..31 and RV64 encodes 0..63.
bext/bexti returns 0 or 1; it does not preserve the original bit position.
Common Usage Scenarios
Bit Operations & Masks
Understand this scenario with real code like «bexti x10, x11, 2 ; x10 = (x11 >> 2) & 1».
Comparison & Detection
Understand this scenario with real code like «bexti x10, x11, 2 ; x10 = (x11 >> 2) & 1».
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
The immediate field width depends on XLEN; RV32 encodes 0..31 and RV64 encodes 0..63.
bext/bexti returns 0 or 1; it does not preserve the original bit position.
FAQ
How is the bit index selected for bexti?
The immediate encodes the bit position directly, with the legal range determined by XLEN.