Source code of Arduino functions - where to look?

Using Arduino Programming Questions
1

Specifically, I'm trying to find source code for these Arduino functions:

micros/millis
sei/cli

Thanks!

2

https://github.com/arduino/Arduino/tree/master/hardware/arduino/cores/arduino

micros/millis is in wiring.c sei/cli are from avr-gcc: avr-libc: <avr/interrupt.h>: Interrupts

3

Yes:
https://github.com/arduino/Arduino/tree/master/hardware/arduino/cores/arduino

micros/millis is in wiring.c sei/cli are from avr-gcc: avr-libc: <avr/interrupt.h>: Interrupts

Thanks a lot! I thought set/cli were Arduino specific functions. I only needed to add #include <avr/interrupt.h> to my code.