Function codeexpval

ThirdParty/lua/lua/lcode.c:793–821

** Code for binary and unary expressions that "produce values" ** (arithmetic operations, bitwise operations, concat, length). First ** try to do constant folding (only for numeric [arithmetic and ** bitwise] operations, which is what 'lua_arith' accepts). ** Expression to produce final result will be encoded in 'e1'. */

** Expression to produce final result will be encoded in 'e1'.
*/
static void codeexpval (FuncState *fs, OpCode op,
                        expdesc *e1, expdesc *e2, int line) {
  lua_assert(op >= OP_ADD);
  if (op <= OP_BNOT && constfolding(fs, op - OP_ADD + LUA_OPADD, e1, e2))
    return;  /* result has been folded */
  else {
    int o1, o2;
    /* move operands to registers (if needed) */
    if (op == OP_UNM || op == OP_BNOT || op == OP_LEN) {  /* unary op? */
      o2 = 0;  /* no second expression */
      o1 = luaK_exp2anyreg(fs, e1);  /* cannot operate on constants */
    }
    else {  /* regular case (binary operators) */
      o2 = luaK_exp2RK(fs, e2);  /* both operands are "RK" */
      o1 = luaK_exp2RK(fs, e1);
    }
    if (o1 > o2) {  /* free registers in proper order */
      freeexp(fs, e1);
      freeexp(fs, e2);
    }
    else {
      freeexp(fs, e2);
      freeexp(fs, e1);
    }
    e1->u.info = luaK_codeABC(fs, op, 0, o1, o2);  /* generate opcode */
    e1->k = VRELOCABLE;  /* all those operations are relocable */
    luaK_fixline(fs, line);
  }
}


static void codecomp (FuncState *fs, OpCode op, int cond, expdesc *e1,