REV
Reverse bytes
This instruction reverses the byte order in a register.
Encoding: Integer
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 |
| 1 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | x | | | | | | | | | | |
sf | | S | | opcode2 | | opc | Rn | Rd |
---|
32-bit (sf == 0 && opc == 10)
REV <Wd>, <Wn>
64-bit (sf == 1 && opc == 11)
REV <Xd>, <Xn>
Decoding algorithm
if opc == '11' && sf == '0' then EndOfDecode(Decode_UNDEF);
constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant integer datasize = 32 << UInt(sf);
constant integer container_size = 8 << UInt(opc);
Operation
constant bits(datasize) operand = X[n, datasize];
bits(datasize) result;
constant integer containers = datasize DIV container_size;
for c = 0 to containers-1
constant bits(container_size) container = Elem[operand, c, container_size];
Elem[result, c, container_size] = Reverse(container, 8);
X[d, datasize] = result;
Explanations
<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 general-purpose source register, encoded in the "Rn" 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 general-purpose source register, encoded in the "Rn" field.Operational Notes
If PSTATE.DIT is 1:
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The execution time of this instruction is independent of:
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The values of the data supplied in any of its registers.
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The values of the NZCV flags.
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The response of this instruction to asynchronous exceptions does not vary based on:
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The values of the data supplied in any of its registers.
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The values of the NZCV flags.