0e3fda6c72
This fixes the majority of cases where we hit the "hlfir.associate of hlfir.expr with more than one use" TODO. In particular, this allows cam4 to be built. hlfir.shape_of is just a way to delay reading shape information until after intrinsics have been lowered to FIR runtime calls. It gets the shape information from reading existing SSA values (e.g. fetching the shape used when hlfir.declare'ing the variable). Therefore hlfir.shape_of doesn't affect decisions about when to deallocate the buffer. Differential Revision: https://reviews.llvm.org/D154521
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.