The above piece code is comment in the file that you shared above:
#if 0 //COMMENTED_CODE
#ifdef IRQMODE
.balign 16
irq_stack:
.rept (SVC_STACK_SIZE + (2 * STACK_SIGNATURE_DATA_SIZE))
.byte 0
.endr
irq_stack_end = .
#endif
#endif //COMMENTED_CODE