A compiler includes a register allocator for allocating registers for instructions in a program to be compiled, and a code generator for generating object code based on the register allocation results performed by the register allocator. The register allocator allocates logical registers for instructions in the program to be compiled, register allocation further allocates, to physical registers, the logical registers that are allocated to the instructions of the program, so that the physical registers that are live at a procedure call in the program to be compiled are allocated from the bottom of the register stack.