rev8
Byte-reverse register (RV64 encoding)
This instruction is defined by:
Synopsis
Reverses the order of the bytes in rs1.
The rev8 mnemonic corresponds to different instruction encodings in RV32 and RV64. |
The byte-reverse operation is only available for the full register width. To emulate word-sized
and halfword-sized byte-reversal, perform a rev8 xd,xs1 followed by a srai xd,xd,K , where K
is XLEN-32 and XLEN-16, respectively.
|
Execution
-
Pruned, XLEN == 64
-
Original
if (implemented?(ExtensionName::B) && (misa.B == 1'b0)) {
raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
}
XReg input = X[xs1];
XReg output = 0;
XReg j = 63;
for (U32 i = 0; i < (56); i = i + 8) {
output[(i + 7):i] = input[j:(j - 7)];
j = j - 8;
}
X[xd] = output;