g++ optimizer report?

John (Eljay) Love-Jensen eljay@adobe.com
Wed Feb 3 13:47:00 GMT 2010


Hi Yue,

You can get a list of toggle-able optimization flags like this:

touch Empty.cpp
gcc -O2 -fverbose-asm -S Empty.cpp -o O2.s
gcc -O3 -fverbose-asm -S Empty.cpp -o O3.s

However, that will not tell you what non-toggle-able optimizations are enabled, since -O2 enables many optimizations that are not controlled by command line flags.  And -O3 enables a few more, as I understand it.

Nor will that tell you what optimization(s) were applied to a particular code segment.

Sincerely,
--Eljay



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