Data processing unit which can access more registers than the registers

Abstract

The data processing unit includes a greater number of physical floating point registers than the number of floating point registers accessible by an instruction, window start point register having a plurality of bits, 1-bit window start pointer valid register, conversion apparatus for converting a floating point register number in an instruction to a physical floating point register number when the value of the window start pointer valid register is 1, and changing the pattern of this conversion by a value obtained from the value of the window start pointer register or the value of a window stride designated in a specific instruction, and the value of the window start pointer register. Also provided is an instruction controller for detecting a window start pointer set instruction for setting a value to the window start pointer register, a floating point register pre-load instruction for converting the floating point register number in the instruction to a physical floating point register number by the conversion circuit from the value obtained from the value of the window start pointer register and the value of the window stride, and storing a main memory data in the physical floating point register indicated by the physical floating point register number.