2d956d2d4e
Some MPI libraries use character dummies + ignore(TKR) to allow passing any kind of buffer. This was meant to already be handled by #108168 However, when the library interface also had an argument requiring an explicit interface, `builder.convertWithSemantics` was not allowed to properly deal with the actual/dummy type mismatch and generated bad IR causing errors like: `'fir.convert' op invalid type conversion'!fir.ref' / '!fir.boxchar\<1\>'`. This restriction was artificial, lowering should just handle any cases allowed by semantics. Just remove 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.