Dynamic assignment across dispatch pipes of source ports to be used to obtain indication of physical registers

Dynamic resource allocation is provided in which additional resources, such as additional architected registers, are provided to an instruction, if it is determined that resources in addition to those configured to be provided to the instruction are to be used for the particular instruction. An instruction to be executed is dispatched on a pipe of a pipeline and that pipe is configured to have a set number of architected registers for use by the instruction. However, if one or more other architected registers are needed, those additional architected registers are dynamically allocated to the instruction by assigning one or more source ports of an additional pipe to the instruction.