<p>The product-group I work for is currently using gcc 3.4.6 (we know it is ancient) for a large low-level c-code base, and want to upgrade to a later version. We have seen performance benefits testing different versions of gcc 4.x on all hardware platforms we tested it on. We are however <em>very</em> scared of c-compiler bugs (for a good reason historically), and wonder if anyone has insight to which version we should upgrade to.</p>

<p>Are people using 4.3.2 for large code-bases and feel that it works fine?</p>

I don't have a specific version for you, but why not have a 4.X
and
3.4.6 installed? Then you could try and keep the code compiling on both versions, and if you run across a show-stopping bug in 4, you have an exit policy.