> From: Richard Guenther [mailto:richard.guent...@gmail.com] > Can we _remove_ a store we percieve as redundant (with a single-threaded > view) with the memory model? Generally yes, so long as synchronization operations either conservatively treated as completely opaque, or are treated correctly in the "single-threaded view". If there is no synchronization between the original store, and the redundant one, then the redundant one changes things only if another thread writes to the same variable in-between. That constitutes a data race, which invokes undefined behavior. The general rule is that any sequentially correct transformation is OK between synchronization operations, so long as you don't store to anything you weren't supposed to modify, and the state at the next synchronization point is what would have been expected. You can sometimes treat synchronizations more aggressively, but that should be safe.
Hans
