The Timer/Counter Interrupt Flag Registers are registers to control timer interruption.
The Timer/Counter Interrupt Flag Registers related codes are defined in hardware/tools/avr/avr/include/avr/iom328p.h as below.
#define TIFR0 _SFR_IO8(0x15) #define TOV0 0 #define OCF0A 1 #define OCF0B 2 #define TIFR1 _SFR_IO8(0x16) #define TOV1 0 #define OCF1A 1 #define OCF1B 2 #define ICF1 5 #define TIFR2 _SFR_IO8(0x17) #define TOV2 0 #define OCF2A 1 #define OCF2B 2
They call _SFR_IO8().