Apparently, there are more problems than -fgcse. "gcc-4.6 -fno-gcse" still fails whereas "gcc-4.4 -fno-gcse" doesn't. I've downgraded the dependency to get a working kernel. Before we upgrade, I think we could use experimental as testing ground to resolve the problems. It's very bad that this kind of bugs reaches wheezy.
The main problem is that we do not know whether gcc-4.x miscompiles kernel or kernel is not properly coded. The -no-gcse only lowers optimization level. It does not fail on my real -amd64 HW neither -i386 inside kvm. Petr