f7daa9d302
Previously an extra block was created by splitting the previous exit block. This produced incorrect results when the outlined region statically never terminated because then there wouldn't be a valid exit block for the outlined region, this caused this newly added block to have an incoming edge from outside of the outlining region, which caused outlining to fail. So far as I can tell this extra block no longer serves any purpose. The comment says it is supposed to collate multiple control flow edges into one place, but the code as it is now does not achieve this. In fact, as can be seen from the changes to lit tests, this block was not actually outlined in the end. This is because there are actually two code extractors: one in the callback for creating a parallel op which is used to find what the input/output variables are (which does have this block added to it), and another one which actually does the outlining (which this block was not added to). Tested with the gfortran and fujitsu test suites. Fixes #112884
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.