{"id":1363,"date":"2013-07-04T13:00:00","date_gmt":"2013-07-04T13:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/vcblog\/2013\/07\/04\/optimizing-c-code-constant-folding\/"},"modified":"2024-09-10T07:57:49","modified_gmt":"2024-09-10T07:57:49","slug":"optimizing-c-code-constant-folding","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/cppblog\/optimizing-c-code-constant-folding\/","title":{"rendered":"Optimizing C++ Code : Constant-Folding"},"content":{"rendered":"

If you have arrived in the middle of this blog series, you might want instead to begin at the <\/span>beginning<\/span><\/a>.<\/span><\/span><\/p>\n

This post examines Constant-Folding – one of the simplest optimizations performed by the VC++ compiler.  In this optimization, the compiler works out the result of an expression while it is compiling (at “compile-time”), and inserts the answer directly into the generated code.  This avoids the cost of performing those same calculations when the program runs (at “runtime”).<\/span><\/span><\/p>\n

Here is an example.  A tiny <\/span>main<\/span> function, stored in the file <\/span>App.cpp<\/span>:<\/span><\/span><\/p>\n

int main() { return 7 + 8; }<\/span><\/p>\n

First, some admin<\/em> about this blog:  <\/span><\/span><\/p>\n