e9cba3c8ed
Fixes #136357 The barrier needs to go between the copying into firstprivate variables and the initialization call for the OpenMP construct (e.g. wsloop). There is no way of expressing this in MLIR because for delayed privatization that is all implicit (added in MLIR->LLVMIR conversion). The previous approach put the barrier immediately before the wsloop (or similar). For delayed privatization, the firstprivate copy code would then be inserted after that, opening the possibility for the race observed in the bug report. This patch solves the issue by instead setting an attribute on the mlir operation, which will instruct openmp dialect to llvm ir conversion to insert a barrier in the correct place.
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.
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Consult the Getting Started with Flang for information on building and running flang.