Final answer:
In x86-64 architecture, the invalid instruction suffixes for 'pop' and 'push' are 'popb/pushb' for byte operations and 'popw/pushw' for word operations as the architecture requires stack operations to be at least 32-bit or 64-bit in size.
Step-by-step explanation:
In x86-64 assembly language, the instructions pop and push are used to remove and add values, respectively, to the stack. However, not all suffixes are valid for these instructions. Specifically, in x86-64 architecture, the pop and push instructions do not support the use of byte (popb and pushb) and word (popw and pushw) suffixes. These are invalid because the architecture requires operations on the stack to be at least 32-bit (dword) or 64-bit (qword) in size. The valid suffixes for these instructions are typically d for dword, and q for qword, corresponding to 32-bit and 64-bit operations respectively