A method includes, in a processor that processes multiple segments of a sequence of instructions of program code, wherein each segment is defined as either speculative or non-speculative, dispatching the instructions of the segments into at least one instruction buffer. The instructions of the segments are executed, and, in each segment, at least some of the executed instructions of the segment are speculatively-committed from the at least one instruction buffer independently of any other segment. Dispatching the instructions includes dispatching the instructions of a first segment into a first region of the at least one instruction buffer, and dispatching the instructions of a second segment, which occurs later in the program code than the first segment, into a second region of the at least one instruction buffer before all the instructions of the first segment have been dispatched into the first region.