rev8
Byte-reverse register (RV64 encoding)
This instruction is defined by:
Synopsis
This instruction 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 rd,rs followed by a srai rd,rd,K, where K
is XLEN-32 and XLEN-16, respectively.
|
Execution
-
Pruned, XLEN == 64
-
Original
if ((%%LINK%csr_field;misa.B;CSR[misa].B%% == 1'b0)) {
%%LINK%func;raise;raise%%(ExceptionCode::IllegalInstruction, %%LINK%func;mode;mode%%(), $encoding);
}
XReg input = X[rs1];
XReg output = 0;
XReg j = 63;
for (U32 i = 0; true; i = 8) {
output[(i + 7):i] = input[j:(j - 7)];
j = j - 8;
}
X[rd] = output;if (%%LINK%func;implemented?;implemented?%%(ExtensionName::B) && (%%LINK%csr_field;misa.B;CSR[misa].B%% == 1'b0)) {
%%LINK%func;raise;raise%%(ExceptionCode::IllegalInstruction, %%LINK%func;mode;mode%%(), $encoding);
}
XReg input = X[rs1];
XReg output = 0;
XReg j = %%LINK%func;xlen;xlen%%() - 1;
for (U32 i = 0; i < (%%LINK%func;xlen;xlen%%() - 8); i = i + 8) {
output[(i + 7):i] = input[j:(j - 7)];
j = j - 8;
}
X[rd] = output;