HLASM: V1R6 Language Ref

DC instruction—Address constantsA location counter reference (*) appears in the fourth constant (*+4096). The valueof the location counter is the address of the first byte of the fourth constant. Whenthe location counter reference occurs in a literal, as in the LM instruction, the valueof the location counter is the address of the first byte of the instruction.Note: It is important to remember that expression evaluation for address constantsis restricted to using 32-bit internal arithmetic. The result is thensign-extended to the length of the constant. This means that certainexpressions in AD-type constants may not yield expected results, especiallyif the resulting value is negative.PSECT reference—R: The R-type constant reserves storage for the address of thePSECT of symbol1 as specified in the associated XATTR statement (“XATTRinstruction (z/OS and CMS)” on page 228). It is the caller’s responsibility toestablish the definition of the R-type address constant referencing the calledroutine’s PSECT, and to pass that address to the called routine. This constant isonly available if the GOFF option is specified.Note: If a program is to be reentrant, R-type address constants may not appear inshared (read-only) text. They should be in the caller’s PSECT, and beprovided to the called routine using an appropriate convention. That is,R-type address constants referring to PSECTs should themselves reside inPSECTs. If not, there can be only a single instantiation of the PSECT workarea, and the program cannot be reentrant.Table 29. R address constantsSubfield Value Example Result1. Duplication factor Allowed2. Type R3. Type Extension D4. Program type Allowed5. ModifiersImplicit length:(length modifiernot present)Alignment:(Length modifiernot present)R-type: 4 bytesRD-type: 8 bytesR-type: FullwordRD-type: DoublewordRange for length: R-type: 3 or 4 onlyRD-type: 3, 4 or 8(no bit length)Range for scale: Not allowedRange for exponent: Not allowed6. Nominal valueRepresented by: An ordinary symbol DC R(PSECT1)Enclosed by: ParenthesesExponent allowed: NoNumber of valuesper operand:MultiplePadding: With zeros at left154 HLASM: V1R6 Language Ref