One embodiment of the present invention provides a system that facilitates deferring execution of instructions with unresolved data dependencies as they are issued for execution in program order. During a normal execution mode, the system issues instructions for execution in program order. Upon encountering an unresolved data dependency during execution of an instruction, the system generates a checkpoint that can subsequently be used to return execution of the program to the point of the instruction. Next, the system executes the instruction and subsequent instructions in an execute-ahead mode, wherein instructions that cannot be executed because of an unresolved data dependency are deferred, and wherein other non-deferred instructions are executed in program order. Upon encountering a store during the execute-ahead mode, the system determines if the store buffer is full. If so, the system prefetches a cache line for the store, and defers execution of the store. If the number of stores that are encountered during execute-ahead mode exceeds the capacity of the store buffer, which means that the store buffer will never have additional space to accept additional stores during the execute-ahead mode because the store buffer is gated, the system directly enters the scout mode, without waiting for the deferred queue to eventually fill.