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The Most Underused Compiler Switches in Visual C++

, March 11, 2014 Microsoft's Visual C++ team explains the nine most underused switches and why you should make sure to include them in your build.
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/LTCG:PGI and /LTCG:PGO

These are linker switches that enable "Profile Guided Optimization," also known as PGO or POGO.

PGO is a runtime compiler optimization that leverages profile data collected from running important or performance-centric user scenarios to build an optimized version of the application. PGO optimizations have some significant advantage over traditional static optimizations as they are based upon how the application is likely to perform in a production environment. This allows optimization for speed on hotter code paths (common user scenarios) and optimization for size on colder code paths (not so common user scenarios), which results in generating both faster and smaller code for the application and significant performance gains.

Additional Comments:

If you care about the runtime performance of your application, you should try out these switches. PGO is the ultimate, highest order of compiler optimization and provides solid gains (CPU, refset, working set, you name it!) for many applications. Browsers (Firefox, Opera, Chrome), compilers and libraries (PHP, Python), and other major applications are also users of PGO.






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