> OK, I'll do some testing with it tomorrow. Which GCC versions are affected?
I tested trunk and an old 4.2.1 internal branch, and found the bug on both, so anything in between would be affected too. It goes back at least to this patch, which mostly fixed the bug: 2008-02-19 Christian Bruel <christian.br...@st.com> Zdenek Dvorak <o...@ucw.cz> * tree-ssa-loop-ivopts.c (may_be_unaligned_p): Check step alignment. (our 4.2.1 branch, plus the above patch, plus your patch, works)