7318074168
`FunctionOpInterface` assumed the fact that the function type (attribute of the operation) can be cloned with arbirary lists of function arguments and results to support argument and result list mutation. This is not always correct, in particular, LLVM dialect functions require exactly one result making it impossible to erase the result. Allow function type cloning to fail and propagate this failure through various APIs that use it. The common assumption is that existing IR has not been modified. Fixes #131142. Reland a8c7ecdcbc3e89b493b495c6831cc93671c3b844 / #136300.
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.