llvm/libcxx/CREDITS.TXT
Mark de Wever abb5dd6e99 Microsoft's floating-point to_chars powered by Ryu and Ryu Printf
Microsoft would like to contribute its implementation of floating-point to_chars to libc++. This uses the impossibly fast Ryu and Ryu Printf algorithms invented by Ulf Adams at Google. Upstream repos: https://github.com/microsoft/STL and https://github.com/ulfjack/ryu .

Licensing notes: MSVC's STL is available under the Apache License v2.0 with LLVM Exception, intentionally chosen to match libc++. We've used Ryu under the Boost Software License.

This patch contains minor changes from Jorg Brown at Google, to adapt the code to libc++. He verified that it works in Google's Linux-based environment, but then I applied more changes on top of his, so any compiler errors are my fault. (I haven't tried to build and test libc++ yet.) Please tell me if we need to do anything else in order to follow https://llvm.org/docs/DeveloperPolicy.html#attribution-of-changes .

Notes:

* libc++'s integer charconv is unchanged (except for a small refactoring). MSVC's integer charconv hasn't been tuned for performance yet, so you're not missing anything.
* Floating-point from_chars isn't part of this patch because Jorg found that MSVC's implementation (derived from our CRT's strtod) was slower than Abseil's. If you're unable to use Abseil or another implementation due to licensing or technical considerations, Microsoft would be delighted if you used MSVC's from_chars (and you can just take it, or ask us to provide a patch like this). Ulf is also working on a novel algorithm for from_chars.
* This assumes that float is IEEE 32-bit, double is IEEE 64-bit, and long double is also IEEE 64-bit.
* I have added MSVC's charconv tests (the whole thing: integer/floating from_chars/to_chars), but haven't adapted them to libcxx's harness at all. (These tests will be available in the microsoft/STL repo soon.)
* Jorg added int128 codepaths. These were originally present in upstream Ryu, and I removed them from microsoft/STL purely for performance reasons (MSVC doesn't support int128; Clang on Windows does, but I found that x64 intrinsics were slightly faster).
* The implementation is split into 3 headers. In MSVC's STL, charconv contains only Microsoft-written code. xcharconv_ryu.h contains code derived from Ryu (with significant modifications and additions). xcharconv_ryu_tables.h contains Ryu's large lookup tables (they were sufficiently large to make editing inconvenient, hence the separate file). The xmeow.h convention is MSVC's for internal headers; you may wish to rename them.
* You should consider separately compiling the lookup tables (see https://github.com/microsoft/STL/issues/172 ) for compiler throughput and reduced object file size.
* See https://github.com/StephanTLavavej/llvm-project/commits/charconv for fine-grained history. (If necessary, I can perform some rebase surgery to show you what Jorg changed relative to the microsoft/STL repo; currently that's all fused into the first commit.)

Differential Revision: https://reviews.llvm.org/D70631
2021-12-12 16:34:50 +01:00

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This file is a partial list of people who have contributed to the LLVM/libc++
project. If you have contributed a patch or made some other contribution to
LLVM/libc++, please submit a patch to this file to add yourself, and it will be
done!
The list is sorted by surname and formatted to allow easy grepping and
beautification by scripts. The fields are: name (N), email (E), web-address
(W), PGP key ID and fingerprint (P), description (D), and snail-mail address
(S).
N: Saleem Abdulrasool
E: compnerd@compnerd.org
D: Minor patches and Linux fixes.
N: Ulf Adams
D: Invented the Ryu and Ryu Printf algorithms used in floating-point to_chars, and wrote the initial code.
N: Muiez Ahmed
E: muiez@ibm.com
D: z/OS port.
N: Dan Albert
E: danalbert@google.com
D: Android support and test runner improvements.
N: Dimitry Andric
E: dimitry@andric.com
D: Visibility fixes, minor FreeBSD portability patches.
N: Holger Arnold
E: holgerar@gmail.com
D: Minor fix.
N: Jorg Brown
D: Ported floating-point to_chars from MSVC to libc++.
N: David Chisnall
E: theraven at theravensnest dot org
D: FreeBSD and Solaris ports, libcxxrt support, some atomics work.
N: Marshall Clow
E: mclow.lists@gmail.com
E: marshall@idio.com
D: C++14 support, patches and bug fixes.
N: Jonathan B Coe
E: jbcoe@me.com
D: Implementation of propagate_const.
N: Matthew Dempsky
E: matthew@dempsky.org
D: Minor patches and bug fixes.
N: Christopher Di Bella
E: cjdb@google.com
E: cjdb.ns@gmail.com
D: Library concepts.
N: Glen Joseph Fernandes
E: glenjofe@gmail.com
D: Implementation of to_address.
N: Eric Fiselier
E: eric@efcs.ca
D: LFTS support, patches and bug fixes.
N: Bill Fisher
E: william.w.fisher@gmail.com
D: Regex bug fixes.
N: Google Inc.
D: Copyright owner and contributor of the CityHash algorithm
N: Howard Hinnant
E: hhinnant@apple.com
D: Architect and primary author of libc++
N: Sergej Jaskiewicz
E: jaskiewiczs@icloud.com
D: Minor improvements in the testing infrastructure
N: Hyeon-bin Jeong
E: tuhertz@gmail.com
D: Minor patches and bug fixes.
N: Argyrios Kyrtzidis
E: kyrtzidis@apple.com
D: Bug fixes.
N: Stephan T. Lavavej
E: stl@microsoft.com
E: stl@nuwen.net
D: Implemented floating-point to_chars.
N: Microsoft Corporation
D: Contributed floating-point to_chars.
N: Bruce Mitchener, Jr.
E: bruce.mitchener@gmail.com
D: Emscripten-related changes.
N: Michel Morin
E: mimomorin@gmail.com
D: Minor patches to is_convertible.
N: Andrew Morrow
E: andrew.c.morrow@gmail.com
D: Minor patches and Linux fixes.
N: Michael Park
E: mcypark@gmail.com
D: Implementation of <variant>.
N: Arvid Picciani
E: aep at exys dot org
D: Minor patches and musl port.
N: Bjorn Reese
E: breese@users.sourceforge.net
D: Initial regex prototype
N: Nico Rieck
E: nico.rieck@gmail.com
D: Windows fixes
N: Jon Roelofs
E: jroelofS@jroelofs.com
D: Remote testing, Newlib port, baremetal/single-threaded support.
N: Kent Ross
E: k@mad.cash
D: Patches for operator<=> support
N: Jonathan Sauer
D: Minor patches, mostly related to constexpr
N: Craig Silverstein
E: csilvers@google.com
D: Implemented Cityhash as the string hash function on 64-bit machines
N: Richard Smith
D: Minor patches.
N: Joerg Sonnenberger
E: joerg@NetBSD.org
D: NetBSD port.
N: Stephan Tolksdorf
E: st@quanttec.com
D: Minor <atomic> fix
N: Ruben Van Boxem
E: vanboxem dot ruben at gmail dot com
D: Initial Windows patches.
N: Michael van der Westhuizen
E: r1mikey at gmail dot com
N: Larisse Voufo
D: Minor patches.
N: Klaas de Vries
E: klaas at klaasgaaf dot nl
D: Minor bug fix.
N: Mark de Wever
E: koraq at xs4all dot nl
D: Format library support.
D: Finalized the porting of MSVC's to_chars to libc++.
N: Zhang Xiongpang
E: zhangxiongpang@gmail.com
D: Minor patches and bug fixes.
N: Xing Xue
E: xingxue@ca.ibm.com
D: AIX port
N: Jeffrey Yasskin
E: jyasskin@gmail.com
E: jyasskin@google.com
D: Linux fixes.
N: Zhihao Yuan
E: lichray@gmail.com
D: Standard compatibility fixes.