5c8c2b3db5
Following the conclusion of the [RFC](https://discourse.llvm.org/t/rfc-names-for-flang-rt-libraries/84321), rename Flang's runtime libraries as follows: * libFortranRuntime.(a|so) to libflang_rt.runtime.(a|so) * libFortranFloat128Math.a to libflang_rt.quadmath.a * libCufRuntime_cuda_${CUDAToolkit_VERSION_MAJOR}.(a|so) to libflang_rt.cuda_${CUDAToolkit_VERSION_MAJOR}.(a|so) This follows the same naming scheme as Compiler-RT libraries (`libclang_rt.${component}.(a|so)`). It provides some consistency between Flang's runtime libraries for current and potential future library components.
39 lines
1.8 KiB
Markdown
39 lines
1.8 KiB
Markdown
<!--===- docs/Real16MathSupport.md
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Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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See https://llvm.org/LICENSE.txt for license information.
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SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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-->
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# Flang support for REAL(16) math intrinsics
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To support most `REAL(16)` (i.e. 128-bit float) math intrinsics Flang relies
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on third-party libraries providing the implementation.
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`-DFLANG_RUNTIME_F128_MATH_LIB=libquadmath` CMake option can be used
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to build `libflang_rt.quadmath` library that has unresolved references
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to GCC `libquadmath` library. A Flang driver built with this option
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will automatically link `libflang_rt.quadmath` and `libquadmath` libraries
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to any Fortran program. This implies that `libquadmath` library
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has to be available in the standard library paths, so that linker
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can find it. The `libquadmath` library installation into Flang project
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distribution is not automatic in CMake currently.
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Testing shows that `libquadmath` versions before GCC-9.3.0 have
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accuracy issues, so it is recommended to distribute the Flang
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package with later versions of `libquadmath`.
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Care must be taken by the distributors of a Flang package built
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with `REAL(16)` support via `libquadmath` because of its licensing
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under the GNU Library General Public License. Moreover, static linking
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of `libquadmath` to the Flang users' programs may imply some
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restrictions/requirements. This document is not intended to give
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any legal advice on distributing such a Flang compiler.
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Flang compiler targeting systems with `LDBL_MANT_DIG == 113`
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may provide `REAL(16)` math support without a `libquadmath`
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dependency, using standard `libc` APIs for the `long double`
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data type. It is not recommended to use the above CMake option
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for building Flang compilers for such targets.
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