I couldn't find any info either. As far as I understand, x264 was doing something that wasn't standard-compliant (array overreads), and the GCC optimization aggressive-loop-optimizations relies on the assumption that all code is standard-compliant. So this is not a GCC bug.
It may be possible to verify this with Valgrind, but I think the version of Valgrind in Ubuntu doesn't support all the instructions that x264 uses yet, so this is requires recompilation without assembly optimizations.
I couldn't find any info either. As far as I understand, x264 was doing something that wasn't standard-compliant (array overreads), and the GCC optimization aggressive- loop-optimizati ons relies on the assumption that all code is standard-compliant. So this is not a GCC bug.
It may be possible to verify this with Valgrind, but I think the version of Valgrind in Ubuntu doesn't support all the instructions that x264 uses yet, so this is requires recompilation without assembly optimizations.