To enhance using efficiency of a stack memory in an information processor.

This information processor 200 is provided with a compression part 240 for discriminating, in a decoder, whether compression information wherein a content of a guarantee register is compressed to indicate evacuation to the stack memory 231 in accompaniment to calling-out of a prescribed function exists in a machine language program, and for compressing the content of the guarantee register to be evacuated to the stack memory 231, when the compression information exists, and an extension part 260 for discriminating, in the decoder, whether extension information wherein the content of the stack memory 231 is extended to indicate restoration to the guarantee register in accompaniment to finish of the calling-out of the prescribed function exists in the machine language program, and for extending the content of the stack memory 231 to be restored to the guarantee register, when the extension information exists.