Arithmetic expression evaluation

Assembler and disassembly expressions are evaluated in 32-bit precision until a 64-bit operand is encountered. At that point, the precision of both operands is converted to 64-bit and all subsequent operators in the expression are evaluated in 64-bit precision. If you want the entire expression evaluated in 64-bit precision, you can use parentheses to alter the order of operations so that the first operand evaluated has at least one 64-bit operand.

If you are running your program on hardware that does not support 64-bit instructions, z/OS® Debugger evaluates the 64-bit arithmetic expressions but you cannot access the 64-bit General Purpose Registers.