bfi

Bit Field Insert

BFI<c> <Rd>, <Rn>, #<lsb>, #<width>

Copies a bitfield into a register.

Pseudocode Operation

width ← msb - lsb + 1
mask ← ((1 << width) - 1)
source_bits ← (Rn AND mask) << lsb
dest_mask ← NOT((mask << lsb))
Rd ← (Rd AND dest_mask) OR source_bits

Example

BFI r0, r1, #0, #width

Encoding

Binary Layout

cond

31:28

0111110

27:21

msb

20:16

15:12

lsb

11:7

001

6:4

3:0

Format Data Proc

Opcode 0x07C00010

Extension A32 (Base)

Operands

Rd
Destination general-purpose register
Rn
First source / base general-purpose register
lsb
Start

Other forms of bfi

bfi Bit Field Insert (Thumb)

Reference

View in Arm A64 ISA Reference ↗ Arm AArch32 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x07C00010	BFI{<c>}{<q>} <Rd>, <Rn>, #<lsb>, #<width>		A32		cond \| 0111110 \| msb \| Rd \| lsb \| 001 \| Rn
0xF3600000	BFI{<c>}{<q>} <Rd>, <Rn>, #<lsb>, #<width>		T32		11110 \| 0 \| 11 \| 01 \| 1 \| 0 \| Rn \| 0 \| imm3 \| Rd \| imm2 \| 0 \| msb

Description

Bit Field Insert copies any number of low order bits from a register into the same number of adjacent bits at any position in the destination register.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    R[d]<msbit:lsbit> = R[n]<(msbit-lsbit):0>;
    // Other bits of R[d] are unchanged

bfi