require_rv64;
require_extension(EXT_XZBP);
require(SHAMT < 32);
reg_t x = RS1;
int shamt = SHAMT;
if (shamt &  1) x = ((x & 0x5555555555555555LL) <<  1) | ((x & 0xAAAAAAAAAAAAAAAALL) >>  1);
if (shamt &  2) x = ((x & 0x3333333333333333LL) <<  2) | ((x & 0xCCCCCCCCCCCCCCCCLL) >>  2);
if (shamt &  4) x = ((x & 0x0F0F0F0F0F0F0F0FLL) <<  4) | ((x & 0xF0F0F0F0F0F0F0F0LL) >>  4);
if (shamt &  8) x = ((x & 0x00FF00FF00FF00FFLL) <<  8) | ((x & 0xFF00FF00FF00FF00LL) >>  8);
if (shamt & 16) x = ((x & 0x0000FFFF0000FFFFLL) << 16) | ((x & 0xFFFF0000FFFF0000LL) >> 16);
WRITE_RD(sext32(x));