IAR has a number of intrinsic routine such as

__enable_interrupts() __disable_interrupts() __watchdog_reset()

These intrinsic functions compile to specific AVR opcodes (SEI, CLI, WDR).

There are equivalent macros that are used in AVR GCC, however they are not located in a single include file.

AVR GCC has sei() for __enable_interrupts(), and cli() for __disable_interrupts(). Both of these macros are located in <avr/interrupts.h>.

AVR GCC has the macro wdt_reset() in place of __watchdog_reset(). However, there is a whole Watchdog Timer API available in AVR GCC that can be found in <avr/wdt.h>.