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Given a TARGET DATA construct with USE_DEVICE_PTR(x) and IF(FALSE), the compiler will crash if `x` was used in the body. The cause of the crash is that the MLIR->LLVM codegen tries to look up the translated value of x, but one had not been mapped. Given an IF clause, the translation will generate an if-then-else construct, with the "else" block corresponding to the false condition, i.e. the host device playing the role of the target device. In that block, still process the USE_DEVICE_ADDR/USE_DEVICE_PTR clauses, which will cause the translation mappings to be created. Fixes https://github.com/llvm/llvm-project/issues/145558
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.