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SEL

Select Bytes selects each byte of its result from either its first operand or its second operand, according to the values of the PSTATE.GE flags.

It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) .

A1

313029282726252423222120191817161514131211109876543210
!= 111101101000RnRd(1)(1)(1)(1)1011Rm
cond

A1

SEL{<c>}{<q>} {<Rd>,} <Rn>, <Rm>

d = UInt(Rd);  n = UInt(Rn);  m = UInt(Rm);
if d == 15 || n == 15 || m == 15 then UNPREDICTABLE;

T1

15141312111098765432101514131211109876543210
111110101010Rn1111Rd1000Rm

T1

SEL{<c>}{<q>} {<Rd>,} <Rn>, <Rm>

d = UInt(Rd);  n = UInt(Rn);  m = UInt(Rm);
if d == 15 || n == 15 || m == 15 then UNPREDICTABLE; // Armv8-A removes UNPREDICTABLE for R13

For more information about the constrained unpredictable behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors.

Assembler Symbols

<c>

See Standard assembler syntax fields.

<q>

See Standard assembler syntax fields.

<Rd>

Is the general-purpose destination register, encoded in the "Rd" field.

<Rn>

Is the first general-purpose source register, encoded in the "Rn" field.

<Rm>

Is the second general-purpose source register, encoded in the "Rm" field.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    R[d]<7:0>   = if PSTATE.GE<0> == '1' then R[n]<7:0>   else R[m]<7:0>;
    R[d]<15:8>  = if PSTATE.GE<1> == '1' then R[n]<15:8>  else R[m]<15:8>;
    R[d]<23:16> = if PSTATE.GE<2> == '1' then R[n]<23:16> else R[m]<23:16>;
    R[d]<31:24> = if PSTATE.GE<3> == '1' then R[n]<31:24> else R[m]<31:24>;
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