[CodeGen] Take the executable stack from a module flag (#215152) AsmPrinter marked `.note.GNU-stack` executable whenever the module had a use of `llvm.init.trampoline`. This was not compliant with the documentation for the function, which causes regressions in Julia. Instead read a new `"executable-stack"` module flag, so that the request comes from the frontend that emitted the code rather than from scanning for an intrinsic and auto-magically (and wrongly) guessing. Update the documentation to be even more clear about this implementation's expectations (which matches gcc's abilities for the same). Frontends generating code that needs an executable stack now have to set the flag for that purpose. For example, flang will do so from BoxedProcedurePass when it emits a stack based trampoline; the `-fsafe-trampoline` runtime pool does not need one (nor was the custom runtime intrinsics really necessary for `-fsafe-trampoline`, since the existing intrinsic was already defined to support that use case too). Fixes a regression caused by #151754, which introduced new behavior onto the existing intrinsics which wasn't permitted by the documentation. Fixes issue with upgrading here: https://github.com/JuliaLang/julia/pull/62563#issuecomment-5220335991 Co-authored-by: Claude Opus 5 <noreply@anthropic.com> GitOrigin-RevId: f532c2d780d3afe589b43cb920fbc445322d47f7
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.
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.