Index

BFC

Bitfield Clear sets a bitfield of <width> bits at bit position <lsb> of the destination register to zero, leaving the other destination bits unchanged.

This is an alias of BFM. This means:

Leaving other bits unchanged
(FEAT_ASMv8p2)

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
sf 0 1 1 0 0 1 1 0 N immr imms 1 1 1 1 1 Rd
opc Rn

32-bit (sf == 0 && N == 0)

BFC <Wd>, #<lsb>, #<width>

is equivalent to

BFM <Wd>, WZR, #(-<lsb> MOD 32), #(<width>-1)

and is the preferred disassembly when UInt(imms) < UInt(immr).

64-bit (sf == 1 && N == 1)

BFC <Xd>, #<lsb>, #<width>

is equivalent to

BFM <Xd>, XZR, #(-<lsb> MOD 64), #(<width>-1)

and is the preferred disassembly when UInt(imms) < UInt(immr).

Assembler Symbols

<Wd>

Is the 32-bit name of the general-purpose destination register, encoded in the "Rd" field.
<Xd>

Is the 64-bit name of the general-purpose destination register, encoded in the "Rd" field.
<lsb>

For the 32-bit variant: is the bit number of the lsb of the destination bitfield, in the range 0 to 31.

For the 64-bit variant: is the bit number of the lsb of the destination bitfield, in the range 0 to 63.
<width>

For the 32-bit variant: is the width of the bitfield, in the range 1 to 32-<lsb>.

For the 64-bit variant: is the width of the bitfield, in the range 1 to 64-<lsb>.

Operation

The description of BFM gives the operational pseudocode for this instruction.

Operational information

If PSTATE.DIT is 1: