18fe0124e7
Make some minor tweaks (inlining, caching) to the formatting input path to improve integer input in a SPEC code. (None of the I/O library has been tuned yet for performance, and there are some easy optimizations for common cases.) Input integer values are now calculated with native C/C++ 128-bit integers. A benchmark that only reads about 5M lines of three integer values each speeds up from over 8 seconds to under 3 in my environment with these changeds. If this works out, the code here can be used to optimize the formatted input paths for real and character data, too. Fixes https://github.com/llvm/llvm-project/issues/134026.
Flang
Flang is a ground-up implementation of a Fortran front end written in modern C++. It started off as the f18 project (https://github.com/flang-compiler/f18) with an aim to replace the previous flang project (https://github.com/flang-compiler/flang) and address its various deficiencies. F18 was subsequently accepted into the LLVM project and rechristened as Flang.
Please note that flang is not ready yet for production usage.
Getting Started
Read more about flang in the docs directory. Start with the compiler overview.
To better understand Fortran as a language and the specific grammar accepted by flang, read Fortran For C Programmers and flang's specifications of the Fortran grammar and the OpenMP grammar.
Treatment of language extensions is covered in this document.
To understand the compilers handling of intrinsics, see the discussion of intrinsics.
To understand how a flang program communicates with libraries at runtime, see the discussion of runtime descriptors.
If you're interested in contributing to the compiler, read the style guide and also review how flang uses modern C++ features.
If you are interested in writing new documentation, follow LLVM's Markdown style guide.
Consult the Getting Started with Flang for information on building and running flang.