FRIDAY, OCTOBER 2, 2026
s390
s390: Enforce register pair constraints for stpq instruction
Assembler now enforces register pair constraints for s390 stpq instruction.
This commit updates the s390 assembler to enforce architectural constraints on the R1 operand for the stpq instruction. It ensures that R1 designates an even-odd pair of general registers and is an even-numbered register, preventing specification exceptions.
In Details
This patch modifies the s390 assembler to enforce the architectural requirement that the stpq instruction's R1 operand must designate an even-odd pair of general registers and be an even-numbered register. This aligns the assembler's validation with the z/Architecture Principles of Operation, preventing specification exceptions.
For Context
- s390
- A family of mainframe computer architectures developed by IBM.
- assembler
- A program that translates assembly language into machine code.
- register pair
- On some architectures, certain instructions require two adjacent registers to function as a single, wider operand. For example, an even-numbered register and the immediately following odd-numbered register can form a pair.
- specification exception
- An error condition detected by the hardware when an instruction is executed with operands or conditions that violate the architecture's rules.
- stpq
- A s390 machine instruction for store packed decimal.