Method and apparatus for improving system performance in data processing system

A computer processing apparatus includes a buffer called a decoded instruction buffer (DIB), which is used to store groups of commands representing instructions that can be executed in parallel. Each pattern in a DIB group may be an encoding of a long instruction termed a long decoded instruction (LDI). The DIB works in conjunction with a conventional computer processing apparatus consisting of a memory system, an instruction queue, and an instruction dispatch unit feeding into a set of execution units. When an instruction is not available in the DIB, this and subsequent instructions are fetched from the memory system into the instruction queue and executed in a conventional way, involving either a subset of available functional units, or functional units dedicated to this purpose. Simultaneous with the execution of instructions by the conventional apparatus, a group formatter creates a set of LDIs, each of which is an alternate encoding of a set of the original instructions which can be executed in parallel. In constructing the LDIs, the group formatter analyzes the dependency between instructions and instruction latency. Each set of LDIs constructed by the group formatter is saved in the DIB so that the next execution of the same set of instructions can be executed directly from the DIB on the full complement of functional units and will not require the effort of dependency and latency analysis.