What’s the difference between the /Ot flag (“favor fast code”) and the /O2 flag (“maximize speed”)?
(Ditto with /Os and /O1.)
What’s the difference between the /Ot flag (favor fast code) and the /O2 flag
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What’s the difference between the /Ot flag (“favor fast code”) and the /O2 flag (“maximize speed”)?
(Ditto with /Os and /O1.)
/O1 and /O2 bundle together a number of options aimed at a larger goal. So /O1 makes a number of code generation choices that favour size; /O2 does the same thing and favours speed.
/O1 includes /Os as well as other options. /O2 includes /Ot as well as other options. Some optimisations are enabled by both /O1 and /O2. And, depending on your program’s paging behaviour, /O1 (size) can result in faster speed than /O2 if paging code comes to dominate your perf over instruction execution cost.
A good short summary of the impact of /O1 and /O2 in VC++ 2010 is here
http://msdn.microsoft.com/en-us/library/8f8h5cxt.aspx
and includes links for other versions of VC.
Martyn