In this blog we will explore one change the MSVC compiler has implemented in an effort to improve the codegen quality of applications in debug mode. We will highlight what the change does, and how it could be extended for the future. If debug performance is something you care about for your C++ projects, then Visual Studio 2022 version 17.5 is making that experience even better!<\/p>\n
Please note that this blog will contain some assembly but being an expert in assembly is not required.<\/em><\/p>\n You might notice that the title of this blog is a play on words based on a recent popular blog post of a similar name,\n“the sad state of debug performance in\nc++”<\/a>. In the blog Vittorio Romeo highlights some general C++ shortcomings when it comes to debugging performance.\nVittorio also also filed this Developer Community ticket “`std::move` (and\nsimilar functions) result in poor debug performance and worse debugging experience<\/a>“; thanks to him and everyone who\nvoted! Much of the reason for the observed slowdown is the cost of abstraction, with the notable example of\n Would generate a function call when the code is conceptually:<\/p>\n The function Overview<\/h2>\n
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Motivation<\/span><\/h2>\n
std::move<\/code> where the following code:<\/p>\nint i = 0;\r\nstd::move(i);<\/pre>\n
int i = 0;\r\nstatic_cast<int&&>(i);<\/pre>\n
std::move<\/code> is conceptually a named cast, much like static_cast but with a contextual meaning for code\naround it. The penalty for using this named cast is that you get a function call generated in the debug assembly.\nHere’s the assembly of the two examples above:<\/p>\n