Jens,

First, Y86 does not have any efx, egx, and ehx registers, which is why you are getting the invalid lines when you pour the code through YAS.

Second, you make conditional branches by subtracting two registers using the subl instruction and jumping on the condition code set by the Y86 ALU by ways of the jxx instructions.

Check my blog at http://y86tutoring.wordpress.com for details.

Translate C code to assembly code?
If $f: \mathbb Q\to \mathbb Q$ is a homomorphism, prove that $f(x)=0$ for all $x\in\mathbb Q$ or $f(x)=x$ for all $x$ in $\mathbb Q$.

I'm wondering if you can help me with this one? 
