FBT_REG_L0
(local) = FBT_REG_L0
while ((locals)[(local) - FBT_REG_L0]) \
(locals)[(local) - FBT_REG_L0] = 1;
*tinstr++ = FBT_MOV(rs1, FBT_REG_L0);
rs1 = FBT_REG_L0;
(locals)[(r) - FBT_REG_L0] = 1;