1. A computer-implemented method, comprising: preparing a portable code sequence corresponding to a source representation of code comprising an atomic transaction, wherein the portable code sequence is platform-independent; and generating a functional sequence executable to perform the atomic transaction in a target execution environment; wherein said preparing comprises: including in the portable code sequence an operation defined by a portable transaction interface, wherein the operation defined by the portable transaction interface is platform-independent; and wherein said generating a functional sequence comprises: including in the functional sequence a call to a function executable to perform the operation defined by the portable transaction interface in the target execution environment in a manner that is dependent on whether it has been determined, at runtime and prior to attempting to perform the operation: that a given best effort hardware transactional memory support mechanism is available to exploit when performing the operation in the target execution environment; or that the given best effort hardware transactional memory support mechanism is not available to exploit when performing the operation in the target execution environment.