Search notes:

gcc -O

`-O0`	(Oh zero): Optimize for compilation time (which is the default optimization mode)
`-O1`	Try to reduce code size and execution time without increasing compilation time too much. (equal to `-O`)
`-O2`	Optimize more
`-O3`	Optimize even more
`-Os`	Optimize for size. See also `-fomit-frame-pointer`.
`-oz`	Opimize more aggresively for size than with `-Os`. Introduced with GCC 12.1
`-Ofast`	implies `-O3 -ffast-math -fno-protect-parens -fallow-store-data-races -fstack-arrays -fno-semantic-interposition`
`-Og`	Optimize for debugging. `-Og` does not imply `-g`.

See also