Release notes for LLVM 11 release

Hi flang-dev

I have pushed up a release notes for Flang for the LLVM 11 branch here for review https://reviews.llvm.org/D84864.

For LLVM 11, I have tried to set the expectation that Flang is experimental in LLVM 11 and not a finished compiler. I feel that conservatively stating that it supports parsing and unparsing only sends this message more clearly than trying to capture the precise details of what codegen and runtime support exists at this point in Flang's development. The document also states that Flang is expected to support all of Fortran + OpenMP + OpenACC for parsing and semantics, even though semantic analysis is not 100% complete at this point. I think this is ok because if a user hit a parsing problem or missing semantic check then we would still want that user to file a bug, unlike in codegen when it would not be useful.

For the format, I took inspiration from the release notes from the other projects but I expect as flang matures the release notes will start to look a bit like clang's, with a stable-ish set of sections covering the broad themes like OpenMP, Fortran language support, optimisations, etc. I have a second patch to add a template file on master for the next release with some suggestions on sections: https://reviews.llvm.org/D84867.

Especially interested if anyone thinks there is anything wrong or missing in the LLVM 11 document.

Happy to take feedback on this thread or on the review.

Ta
Rich

Richard Barton
Principal Engineer - Arm Compiler for Linux
Arm Manchester