1. An apparatus comprising: an execution unit; a plurality of storage elements, including a storage element configured to store information indicative of a first execution dependency between a first floating-point instruction and a second floating-point instruction in an instruction stream; wherein an initial one of the first and second floating-point instructions in the instruction stream specifies a first portion of a logical register as a destination, and the other, subsequent one of the first and second floating-point instructions collectively specifies at least the first portion and a second portion of the logical register as a source; wherein the apparatus is configured, in response to information indicative of the first execution dependency stored in the storage element, to insert one or more instructions into the instruction stream between the first and second floating-point instructions; and wherein the inserted one or more instructions are executable by the execution unit to cause a physical register within the apparatus to receive first and second floating-point values that are to be used collectively as a value of the source specified by the subsequent one of the first and second floating-point instructions.