1. A non-transitory computer-readable storage medium storing program instructions executable by a processor to implement: a transactional memory system speculatively executing memory access operations of an atomic memory transaction, wherein said executing comprises buffering respective pre-transaction values of memory addresses accessed by the memory access operations; pausing execution of the atomic memory transaction; and a debugger tool replaying one or more of the memory access operations, wherein said replaying is dependent on determining the respective pre-transactional values stored by the transactional memory system for the respective memory addresses accessed by the one or more of the memory access operations.