In this post, we will see how to resolve Can switch default statement be optimised out for enum Question: If I have a switch statement that handles all enum cases explicitly, is the compiler allowed to optimise away the default ...

In this post, we will see how to resolve Compiler optimizations may cause integer overflow. Is that okay? Question: I have an int x. For simplicity, say ints occupy the range -2^31 to 2^31-1. I want to compute 2*x-1. I ...

In this post, we will see how to resolve What kind of program can benefit much from LTO? Question: When using dhrystone to get DMIPS, I found that LTO greatly impacted the results. LTO-dhrystone is nearly 4x LTO-less-dhrystone: without LTO ...

Question: Possible Duplicate: Why does volatile exist? I have never used it but I wonder why people use it? What does it exactly do? I searched the forum, I found it only C# or Java topics. Best Answer: Consider this ...

Question: I first noticed in 2009 that GCC (at least on my projects and on my machines) have the tendency to generate noticeably faster code if I optimize for size (-Os) instead of speed (-O2 or -O3), and I have ...

Question: I was implementing an algorithm in Swift Beta and noticed that the performance was very poor. After digging deeper I realized that one of the bottlenecks was something as simple as sorting arrays. The relevant part is here: In ...

Question: I was looking for the fastest way to popcount large arrays of data. I encountered a very weird effect: Changing the loop variable from unsigned to uint64_t made the performance drop by 50% on my PC. The Benchmark As ...

Question: I am doing some numerical optimization on a scientific application. One thing I noticed is that GCC will optimize the call pow(a,2) by compiling it into a*a, but the call pow(a,6) is not optimized and will actually call the ...

Question: I wish to mark a function for more aggressive optimizations. The function is not called often, so PGO won’t help, but I still want it as low latency as possible. gcc has attribute hot for this. Is there some ...

Question: Test Code: I want to make arr[0] as efficient as C style array, which means inline STL array [] operator function. I have checked the generate assembly code: arr[9] is a function call 1d <test(std::array<int, 10ul> const&)+0x1d> in generated ...