srimeruva@xxxxxxxxxxxxxx writes: > what is the advantage of using match_dup for internal operands as > > (define_expand "zero_extendhisi2" > [(set (match_operand:SI 0 "register_operand" "") > (and:SI (subreg:SI > (match_operand:HI 1 "register_operand" "") > 0) > (match_dup 2)))] > "" > "operands[2] > = force_reg (SImode, GEN_INT (65535)); ") This would normally be used for a named pattern which does not expect operand[2] to be filled in. Since there is no operand[2], using a match_operand does not make sense. But since operand[2] needs to be referenced in the generated pattern, it has to appear somehow. match_dup is a reasonable compromise, because match_dup always matches. Ian
