Sometimes -O3 produces slower code than -O2. Sometimes it produces incorrect cod... | Hacker News

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		michael_h on Jan 8, 2016 \| parent \| context \| favorite \| on: How to C in 2016 Sometimes -O3 produces slower code than -O2. Sometimes it produces incorrect code. I usually compile with -O2 and annotate certain functions with O3 - if it looks like vectorization will give the function a boost.

ahoka on Jan 8, 2016 [–]

To be honest I don't understand why isn't -O2 the default. Also does anyone ever use -O1?!

astrange on Jan 9, 2016 | [–]

-O1 is good for debugger compatibility, and for avoiding compiler bugs at higher levels.

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