Instruction set avr1 is for the minimal AVR core, not supported by the C compiler, only for assembler programs (MCU types: at90s1200, attiny11, attiny12, attiny15, attiny28).
Instruction set avr2 (default) is for the classic AVR core with up to 8K program memory space (MCU types: at90s2313, at90s2323, at90s2333, at90s2343, attiny22, attiny26, at90s4414, at90s4433, at90s4434, at90s8515, at90c8534, at90s8535).
Instruction set avr25 is for the classic AVR core with up to 8K program memory space plus the MOVW instruction (MCU types: attiny13, attiny13a, attiny2313, attiny2313a, attiny24, attiny24a, attiny4313, attiny44, attiny44a, attiny84, attiny84a, attiny25, attiny45, attiny85, attiny261, attiny261a, attiny461, attiny461a, attiny861, attiny861a, attiny87, attiny43u, attiny48, attiny88, at86rf401, ata6289).
Instruction set avr3 is for the classic AVR core with up to 128K program memory space (MCU types: at43usb355, at76c711).
Instruction set avr31 is for the classic AVR core with exactly 128K program memory space (MCU types: atmega103, at43usb320).
Instruction set avr35 is for classic AVR core plus MOVW, CALL, and JMP instructions (MCU types: attiny167, at90usb82, at90usb162, atmega8u2, atmega16u2, atmega32u2).
Instruction set avr4 is for the enhanced AVR core with up to 8K program memory space (MCU types: atmega48, atmega48a, atmega48p, atmega8, atmega88, atmega88a, atmega88p, atmega88pa, atmega8515, atmega8535, atmega8hva, at90pwm1, at90pwm2, at90pwm2b, at90pwm3, at90pwm3b, at90pwm81).
Instruction set avr5 is for the enhanced AVR core with up to 128K program memory space (MCU types: atmega16, atmega16a, atmega161, atmega162, atmega163, atmega164a, atmega164p, atmega165, atmega165a, atmega165p, atmega168, atmega168a, atmega168p, atmega169, atmega169a, atmega169p, atmega169pa, atmega32, atmega323, atmega324a, atmega324p, atmega325, atmega325a, atmega325p, atmega3250, atmega3250a, atmega3250p, atmega328, atmega328p, atmega329, atmega329a, atmega329p, atmega329pa, atmega3290, atmega3290a, atmega3290p, atmega406, atmega64, atmega640, atmega644, atmega644a, atmega644p, atmega644pa, atmega645, atmega645a, atmega645p, atmega6450, atmega6450a, atmega6450p, atmega649, atmega649a, atmega649p, atmega6490, atmega6490a, atmega6490p, atmega16hva, atmega16hva2, atmega16hvb, atmega32hvb, atmega64hve, at90can32, at90can64, at90pwm216, at90pwm316, atmega32c1, atmega64c1, atmega16m1, atmega32m1, atmega64m1, atmega16u4, atmega32u4, atmega32u6, at90usb646, at90usb647, at94k, at90scr100).
Instruction set avr51 is for the enhanced AVR core with exactly 128K program memory space (MCU types: atmega128, atmega1280, atmega1281, atmega1284p, atmega128rfa1, at90can128, at90usb1286, at90usb1287, m3000).
Instruction set avr6 is for the enhanced AVR core with a 3-byte PC (MCU types: atmega2560, atmega2561).
rjmp/rcallinstructions with 8K wrap-around.