Producing the fastest possible executable

Question

I have a very large program which I have been compiling under visual studio (v6 then migrated to 2008). I need the executable to run as fast as possible. The program spends most of its time processing integers of various sizes and does very little IO.

Obviously I will select maximum optimization, but it seems that there are a variety of things that can be done which don't come under the heading of optimization which do still affect the speed of the executable. For example selecting the __fastcall calling convention or setting structure member alignment to a large number.

So my question is: Are there other compiler/linker options I should be using to make the program faster which are not controlled from the "optimization" page of the "properties" dialog.

EDIT: I already make extensive use of profilers.

Answer 1

Another optimization option to consider is optimizing for size. Sometimes size-optimized code can run faster than speed-optimized code due to better cache locality.

Also, beyond optimization operations, run the code under a profiler and see where the bottlenecks are. Time spent with a good profiler can reap major dividends in performance (especially it if gives feedback on the cache-friendliness of your code).

And ultimately, you'll probably never know what "as fast as possible" is. You'll eventually need to settle for "this is fast enough for our purposes".

Answer 2

Profile-guided optimization can result in a large speedup. My application runs about 30% faster with a PGO build than a normal optimized build. Basically, you run your application once and let Visual Studio profile it, and then it is built again with optimization based on the data collected.