Arm Compiler armasm User Guide : 16.29 BFI

16.29 BFI

Bitfield Insert.

This instruction is an alias of BFM.

The equivalent instruction is BFM Wd, Wn, #(-lsb MOD 32), #(width-1).

Syntax

BFI Wd, Wn, #lsb, #width ; 32-bit

BFI Xd, Xn, #lsb, #width ; 64-bit

Where:

Wd

Is the 32-bit name of the general-purpose destination register.

Wn

Is the 32-bit name of the general-purpose source register.

lsb

Depends on the instruction variant:

32-bit general registers: Is the bit number of the lsb of the destination bitfield, in the range 0 to 31.
64-bit general registers: Is the bit number of the lsb of the destination bitfield, in the range 0 to 63.

width

Depends on the instruction variant:

32-bit general registers: Is the width of the bitfield, in the range 1 to 32-lsb.
64-bit general registers: Is the width of the bitfield, in the range 1 to 64-lsb.

Xd

Is the 64-bit name of the general-purpose destination register.

Xn

Is the 64-bit name of the general-purpose source register.

Usage

Bitfield Insert copies any number of low-order bits from a source register into the same number of adjacent bits at any position in the destination register, leaving other bits unchanged.

Related references

16.30 BFM

16.1 A64 instructions in alphabetical order

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