If it weren&#x27;t for the &quot;fastcall&quot; convention using ECX for an actual argument value, they could have used &quot;MOV ECX,EDI&quot; and then the change to a &quot;JMP $-5&quot; would have been possible with a single byte store to the opcode (0x89 -&gt; 0xeb), removing any worries about a two-byte store straddling a cache-line or page boundary.