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EXTR

Extract register extracts a register from a pair of registers.

This instruction is used by the alias ROR (immediate).

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sf00100111N0RmimmsRnRd

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

EXTR <Wd>, <Wn>, <Wm>, #<lsb>

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

EXTR <Xd>, <Xn>, <Xm>, #<lsb>

integer d = UInt(Rd);
integer n = UInt(Rn);
integer m = UInt(Rm);
integer datasize = if sf == '1' then 64 else 32;
integer lsb;

if N != sf then UNDEFINED;
if sf == '0' && imms<5> == '1' then UNDEFINED;
lsb = UInt(imms);

Assembler Symbols

<Wd>

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

<Wn>

Is the 32-bit name of the first general-purpose source register, encoded in the "Rn" field.

<Wm>

Is the 32-bit name of the second general-purpose source register, encoded in the "Rm" field.

<Xd>

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

<Xn>

Is the 64-bit name of the first general-purpose source register, encoded in the "Rn" field.

<Xm>

Is the 64-bit name of the second general-purpose source register, encoded in the "Rm" field.

<lsb>

For the 32-bit variant: is the least significant bit position from which to extract, in the range 0 to 31, encoded in the "imms" field.

For the 64-bit variant: is the least significant bit position from which to extract, in the range 0 to 63, encoded in the "imms" field.

Alias Conditions

AliasIs preferred when
ROR (immediate)Rn == Rm

Operation

bits(datasize) result;
bits(datasize) operand1 = X[n];
bits(datasize) operand2 = X[m];
bits(2*datasize) concat = operand1:operand2;

result = concat<lsb+datasize-1:lsb>;

X[d] = result;

Operational information

If PSTATE.DIT is 1:

  • The execution time of this instruction is independent of:
    • The values of the data supplied in any of its registers.
    • The values of the NZCV flags.
  • The response of this instruction to asynchronous exceptions does not vary based on:
    • The values of the data supplied in any of its registers.
    • The values of the NZCV flags.
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