A system and method for producing a fused instruction is described. In one
embodiment, a first instruction and a second instruction that are both
simple instructions (e.g., perform only one operation) and are dependent
are fused together to create the fused instruction. The fused instruction
has an opcode that represents the operation performed by the first
instruction and the operation performed by the second instruction. The
fused instruction has three source operands and one destination operand.
Two of the three source operands are the two source operands of the first
instruction, and the third source operand is the source operand of the
second instruction that is not the destination operand of the first
instruction. The destination operand of the fused instruction is the
destination operand of the second instruction. An execution unit that can
execute a fused instruction in one clock cycle is also disclosed. In one
embodiment, the execution unit has two arithmetic logic units ("ALUs"),
each of the ALUs performs one of the two operations of the fused
instruction. The result of the first ALU is input into the second ALU to
produce the desired result.