The ARCH option specifies the architecture for which the executable program's instructions are to be generated. It allows the optimizer to take advantage of specific hardware instruction sets. A subparameter specifies the group to which a model number belongs.
.-5-. >>-ARCH--(--+-n-+--)-------------------------------------------><
The current values that may be specified for the ARCH level are:
Specifically, these ARCH(5) machines and their follow-ons include instructions such as NILL, NILH, OILL, OILH, LLILL and LLILH.
Specifically, the compiler on these ARCH(6) machines and their follow-ons may exploit the long-displacement instruction set. The long-displacement facility provides a 20-bit signed displacement field in 69 previously existing instructions (by using a previously unused byte in the instructions) and 44 new instructions. A 20-bit signed displacement allows relative addressing of up to 524,287 bytes beyond the location designated by a base register or base and index register pair and up to 524,288 bytes before that location. The enhanced previously existing instructions generally are ones that handle 64-bit binary integers. The new instructions generally are new versions of instructions for 32-bit binary integers. The new instructions also include
The long-displacement facility provides register-constraint relief by reducing the need for base registers, code size reduction by allowing fewer instructions to be used, and additional improved performance through removal of possible address-generation interlocks.
Specifically, these ARCH(7) machines and their follow-ons add instructions supported by facilities such as extended-immediate and extended translation facilities, which may be exploited by the compiler. For further information on these facilities, refer to z/Architecture Principles of Operation.
ARCH(7) machines also support the DFP instructions.
Specifically, these ARCH(8) machines and their follow-ons add instructions supported by the general instruction extensions facility, which may be exploited by the compiler. Also, these machines add instructions supported by the decimal floating-point facility, which are generated if the DFP compiler option is specified and there are decimal floating-point data types in the source code. For further information on these facilities, refer to z/Architecture Principles of Operation.
If you specify an ARCH value less than 5, the compiler will reset it to 5.