[flang] Add TRANSFER folding value tests for MOLD longer than SOURCE (#213573) Constant folding of TRANSFER has value tests for same-size and mold-shorter cases (flang/test/Evaluate/fold-transfer.f90) and shape tests (folding10.f90), but nothing pins the result values when the physical representation of the result is longer than SOURCE's. F2023 16.9.212 p.5 makes the leading part normative (including the TRANSFER(TRANSFER(E,D),E) round-trip identities), and the Examples paragraph's Case (ii) pins a partially covered trailing array element; flang zero-fills the processor-dependent remainder (scalar, array, derived, and CHARACTER molds, including derived-type components wholly beyond SOURCE's representation). All checks are byte-order independent: round trips prove leading-part placement, and the two-endian .or. checks (the fold-transfer.f90 test_c2i_s idiom) are portable value/zero-fill pins. These tests pass at head; their purpose is to guard these semantics through upcoming refactoring of the Evaluate library's scalar representation and initial-image machinery (see the discussion on PR #212956 and the restaging of PR #206907). Assisted-by: AI GitOrigin-RevId: 540aaf1bcab4a8c0c7f994caa486829bd5988ea0
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.