b2c9a58b8f
Currently we don't check for the presence of descriptor/BoxTypes before emitting stores which lower to memcpys, the issue with this is that users can have optional arguments, where they don't provide an input, making the argument effectively null. This can still be mapped and this causes issues at the moment as we'll emit a memcpy for function arguments to store to a local variable for certain edge cases, when we perform this memcpy on a null input, we cause a segfault at runtime. The fix to this is to simply create a branch around the store that checks if the data we're copying from is actually present. If it is, we proceed with the store, if it isn't we skip it.
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.