ATtiny2313 vs ATtiny84 software compatibility
As described in the AVR 8-bit Instruction Set document, only "Reduced Core tinyAVR" parts have different timing from the others. Parts that fall under this designation are the ATtiny4, ATtiny5, ATtiny9, and ATtiny10.

Both the '2313 and '84 are "avr25" architecture as defined by GCC, so their instruction sets are 100% compatible.