HLASM: V1R6 Language Ref

OPSYN instruction||||||v An operation code described in this chapter, or any machine instruction(such as those described in Chapter 4, “Machine instruction statements,” onpage 75), or Chapter 9, “How to write conditional assembly instructions,” onpage 315v The operation code defined by a previous OPSYN instructionv The name of a previously defined macro.operation_code_2is one of these:v An operation code described in this chapter, or any machine instruction(such as those described in Chapter 4, “Machine instruction statements,” onpage 75), or Chapter 9, “How to write conditional assembly instructions,” onpage 315v The operation code defined by a previous OPSYN instructionv The name of a previously defined macro.In the first format, the OPSYN instruction assigns the properties of the operationcode denoted by operation_code_2 to the ordinary symbol denoted by symbol or theoperation code denoted by operation_code_1.In the second format, the OPSYN instruction causes the operation code specified inoperation_code_1 to lose its properties as an operation code.The OPSYN instruction can be coded anywhere in the program to redefine anoperation code.The symbol in the name field can represent a valid operation code. It loses itscurrent properties as if it had been defined in an OPSYN instruction with aspace-filled operand field. In the following example, L and LR both possess theproperties of the LR machine instruction operation code:L OPSYN LRWhen the same symbol appears in the name field of two OPSYN instructions, thelatest definition takes precedence. In the example below, STORE now represents theSTH machine operation:STORE OPSYN STSTORE OPSYN STHNote: OPSYN is not processed during lookahead mode (see “Lookahead” on page336). Therefore it cannot be used during lookahead to replace an opcode thatmust be processed during lookahead, such as COPY. For example, assumingAFTER is defined in COPYBOOK, the following code gives an ASMA042Eerror (Length attribute of symbol is unavailable):AIF (L’AFTER LT 2).BEYONDOPCOPY OPSYN COPY OPSYN not processed during look aheadOPCOPY COPYBOOK OPCOPY fails.BEYOND ANOP ,Redefining conditional assembly instructionsA redefinition of a conditional assembly instruction only comes into effect in macrodefinitions occurring after the OPSYN instruction. The original definition is alwaysused when a macro instruction calls a macro that was defined and edited beforethe OPSYN instruction.198 HLASM: V1R6 Language Ref