How to compile arithmetic expressions to x86?

hi prog, say I want to take as given some variables on the stack x,y,z,w and compile expressions (x+y)*(z+w) to x86 asm.

first off the instructions take registers or pointers and well x86 is weird and has instructions like this:

add x, y ;x OR y must be a register, result in x
mul x ;multiplies eax with x, result is put into eax

so this would work:

mov eax, stack0
add eax, stack1
mov ebx, stack2
add ebx, stack3
mul ebx

but how would you make an algorithm to do this in general?

some variables on the stack

The question you should be asking yourself is why aren't they in the registers already?

If you don't need x again (or one of the other ones, similarly), this uses one less register:
mov eax, [ebp+_y]
add [ebp+_x], eax
mov eax, [ebp+_z]
add eax, [ebp+_w]
mul [ebp+_x]

The general algorithm depends on how many of those values will need to be used after that single expression. It produces a dataflow graph and then matches the available instructions against it.