1. A microprocessor comprising: an instruction window having a plurality of instruction positions, the instruction positions containing anyone of a load instruction, a store instruction, and a load/store instruction, or none of these; and a load/store unit having an address buffer that retains address information of said load instruction, store instruction, or load/store instruction that corresponds to said instruction positions, information positions that store first information indicating whether or not content of said address buffer is valid and second information indicating which instruction the content of said address buffer is about, and an address comparator, wherein: in said load/store unit when an instruction is read in an instruction position of said instruction window, said address buffer is assigned to said instruction and said address buffer is released when said instruction is retired, when said instruction is a load instruction with a determined address, said load instruction is set in said assigned address buffer, an address of a preceding store or load/store instruction is compared with an address of said load instruction, and a read request is made to a memory when compared addresses do not match, when said instruction is a store instruction with a determined address, said store instruction is set in an assigned address buffer, stored data are obtained, and a write request is made to said memory after all preceding instructions in said instruction window are retired, when said instruction is a load/store instruction with a determined common address, said store instruction is set in an assigned address buffer, an address of a preceding store or load/store instruction is compared with the address of said load/store instruction, and a read request is made to said memory system when the compared addresses do not match, the read request result is processed, stored data are obtained, and a write request is made to said memory system after all preceding instructions in said instruction window are retired.