ASM Community

I want to subtract 2 64 bit numbers with borrow and looking for a way to do this using least possible instructions.

The number I want to subtract from is stored in EDX:EAX and the number to subtract with is a QWORD in memory.

So I want:

result = EDX:EAX - 8 byte memory

I was thinking to use MMX for this because I need later to do 64 bit compares aswell but I guess I need to put the values on stack first to load them with movq.
The result could be either in one of the mmx registers or just back in EDX:EAX.

Maybe some of you got some suggestions which is the fastest way to do this?

Thanks in advance.

// CyberHeg