Может это выключить -fschedule-insns (-fno-schedule-insns)? -fschedule-insns
If supported for the target machine, attempt to reorder instructions to eliminate execution stalls due to required data being unavailable. This helps machines that have slow floating point or memory load instructions by allowing other instructions to be issued until the result of the load or floating-point instruction is required.
Enabled at levels -O2, -O3.
и подобное -fschedule-insns2