January 2017 marks the sixth birthday of my desktop computer. When I purchased my trusty Intel Core i5-2500K, I would’ve never guessed that I’d use it for that long. However, rather than jumping to the recently released Kaby Lake CPUs, I’m building my new workstation around two Intel Xeon E5-2670s. Why Xeon? There’s several reasons I went with a dual Xeon setup rather than a flagship i5 or i7. The first reason is that I’m not building a gaming rig but a workstation....
Pointer analysis is an important topic in compiler optimization. One interesting aspect is the dynamic scope of pointers. LLVM differentiates between two situations: Pointer Capture: A pointer value is captured if the function makes a copy of any part of the pointer that outlives the call. Pointer Escape: A pointer value escapes if it is is accessible from outside the current function or thread. The latter case is sometimes considered separate and called thread-escape....
The C++ standard guarantees that the members of a class or struct appear in memory in the same order as they are declared. Nonstatic data members of a (non-union) class with the same access control are allocated so that later members have higher addresses within a class object. The order of allocation of non-static data members with different access control is unspecified. Implementation alignment requirements might cause two adjacent members not to be allocated immediately after each other; so might requirements for space for managing virtual functions and virtual base classes....
The new C++17 standard brings many exciting new features. A smaller, more subtle improvement it brings is guaranteed copy elision. The keyword is guaranteed, as copy elision itself has always been part of the standard. Although it might not be a change as radical as, say, structured bindings, I’m very happy to see it made it into the standard. Copy Elision Before discussing what changed in the latest version of the standard, it might be useful to revisit the basics of copy elision as they are currently defined by the C++14 standard....
In a previous blog post I wrote about bitcode. Embedding it was already possible for quite some time with Apple’s fork of LLVM that ships with Xcode. Recently, Apple upstreamed (parts of) their implementation making it possible to do the same with the open source clang compiler. However, there are some differences between the two implementations. Bitcode embedded with Apple’s version of clang is bundled into a xar-archive. Metadata such as compiler commands used to create the binary and dylibs which the code linked against, are kept in the archive’s table of content....
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Little over a year ago, Apple announced at WWDC 2015 the ability to embed bitcode in Mach-O files. Bitcode is the intermediate representation used by the LLVM compiler and contains all the information required to recompile an application. Having the bitcode present, in addition to machine code, Apple can further optimize applications by compiling and linking specifically for the user’s target device. This is one approach to app thinning, which aims to achieve smaller binaries and therefore more free space on your iDevice....
Self-Adaptive Opportunistic Offloading for Cloud-Enabled Smart Mobile Applications with Probabilistic Graphical Models at Runtime I’m proud to announce that the paper summarizing the findings in my master’s thesis (Intelligent Offloading Decisions for Mobile Cloud Applications) will be presented at the 49th Hawaii International Conference on System Sciences (HICSS). Abstract: Although extensive progress has been made in Mobile Cloud Augmentation, automated decision support on the device that enables the opportunistic and intelligent use of cloud resources is missing....
Clang is everywhere; It is the core of my favorite Vim plugin YouCompleteMe, it recently got supported by Microsoft Visual Studio, it is mentioned in numerous episodes of CppCast and it powers the excellent clang formatter. Naturally, I wanted to get a better understanding of how the clang front end works under the hood. Clang Front End & AST Clang is a C language family front end for LLVM. In compiler design, a front end takes care of the analysis part, which means breaking up the source code into pieces according to a grammatical structure....
If you’re like me and have (1) been using Vim for a while and (2) have been programming in C++, you’ve likely heard about YouCompleteMe. YCM is an awesome auto-completion engine for Vim. For C++ and other C-based languages it uses the libclang under the hood, but it integrates with other engines as well to support C#, Python and Go to name a few. If you’re not yet convinced, check out the author’s website and this blog post....