1. A computer-implemented method comprising: determining that two or more machine instructions of an instruction stream are eligible for optimization, wherein the being eligible comprises determining that the two or more machine instructions comprise a first instruction specifying a first target register and a second instruction specifying the first target register as a source register and a target register, wherein the second instruction is a next sequential instruction of the first instruction in program order, wherein the first instruction specifies a first function to be performed, and the second instruction specifies a second function to be performed; merging the two or more machine instructions into a single optimized internal instruction that is configured to perform the first and second functions of the two or more machine instructions employing operands specified by the two or more machine instructions, wherein the single optimized internal instruction specifies the first target register only as a single target register, wherein the single optimized internal instruction specifies the first and second functions to be performed, and the single optimized internal instruction is stored in a single slot in an issue queue; and executing the single optimized internal instruction to perform the first and second functions of the two or more machine instructions, the executing including fetching the single optimized internal instruction from the queue and generating from the single optimized internal instruction two or more separate internal instructions corresponding to the two or more machine instructions of the instruction stream.