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https://github.com/nlohmann/json.git
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Niels Lohmann
6548a65b46
With the builder of accept() in the same translation unit, GCC 16's interprocedural constant propagation cloned scan_string_vector without its plain argument (always string_plain()). The parse loop of json_document::parse() then called the clone, and GCC generated different code for the whole loop: 0.7-1.2 % more instructions (twitter, citm_catalog, instruments, tree-pretty, canada) and up to +13 % time on citm_catalog. NLOHMANN_VIEW_NOCLONE (GCC only) keeps the function as written; the instruction counts of parse() are then those of develop again. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
90 lines
3.7 KiB
C++
90 lines
3.7 KiB
C++
// __ _____ _____ _____
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// __| | __| | | | JSON for Modern C++
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// | | |__ | | | | | | version 3.12.0
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// |_____|_____|_____|_|___| https://github.com/nlohmann/json
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//
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// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
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// SPDX-License-Identifier: MIT
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#pragma once
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// Macros of json_view.hpp and its detail headers. json.hpp undefines its own
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// macros at its end (macro_unscope.hpp), so the view defines the few it needs
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// under its own prefix; json_view.hpp undefines them all at its end
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// (detail/view/macro_unscope.hpp). Configuration that json.hpp undefines is
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// read from detail::abi_config instead.
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#if (defined(__cplusplus) && __cplusplus >= 201703L) || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
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#define NLOHMANN_VIEW_HAS_CPP_17 1
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#else
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#define NLOHMANN_VIEW_HAS_CPP_17 0
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#endif
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#if defined(__GNUC__) || defined(__clang__)
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#define NLOHMANN_VIEW_LIKELY(x) __builtin_expect(!!(x), 1)
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#define NLOHMANN_VIEW_UNLIKELY(x) __builtin_expect(!!(x), 0)
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#define NLOHMANN_VIEW_ALWAYS_INLINE inline __attribute__((always_inline))
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#define NLOHMANN_VIEW_NOINLINE __attribute__((noinline))
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#elif defined(_MSC_VER)
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#define NLOHMANN_VIEW_LIKELY(x) (x)
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#define NLOHMANN_VIEW_UNLIKELY(x) (x)
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// plain inline: __forceinline makes MSVC report C4714 (not inlined) for
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// function templates it cannot inline, which is an error under /WX; the
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// forced inlining is only a performance hint
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#define NLOHMANN_VIEW_ALWAYS_INLINE inline
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#define NLOHMANN_VIEW_NOINLINE __declspec(noinline)
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#else
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#define NLOHMANN_VIEW_LIKELY(x) (x)
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#define NLOHMANN_VIEW_UNLIKELY(x) (x)
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#define NLOHMANN_VIEW_ALWAYS_INLINE inline
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#define NLOHMANN_VIEW_NOINLINE
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#endif
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// GCC: a function compiled as written, without the clones in which interprocedural
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// constant propagation drops an argument that every caller passes as the same constant
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// (calling such a clone changes the code GCC generates for the parse loop that calls it)
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#if defined(__GNUC__) && !defined(__clang__)
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#define NLOHMANN_VIEW_NOCLONE __attribute__((noclone))
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#else
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#define NLOHMANN_VIEW_NOCLONE
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#endif
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#if defined(__GNUC__) || defined(__clang__)
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#define NLOHMANN_VIEW_NODISCARD __attribute__((warn_unused_result))
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#elif defined(_MSC_VER)
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#define NLOHMANN_VIEW_NODISCARD _Check_return_
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#else
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#define NLOHMANN_VIEW_NODISCARD
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#endif
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// exceptions as in json.hpp (JSON_NOEXCEPTION, JSON_THROW_USER)
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#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND)) && !defined(JSON_NOEXCEPTION)
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#define NLOHMANN_VIEW_THROW(exception) throw exception
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#else
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#include <cstdlib>
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// (the exception is built first, so that the arguments of the throwing
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// helpers count as used; the program ends anyway)
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#define NLOHMANN_VIEW_THROW(exception) (static_cast<void>(exception), std::abort())
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#endif
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#if defined(JSON_THROW_USER)
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#undef NLOHMANN_VIEW_THROW
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#define NLOHMANN_VIEW_THROW JSON_THROW_USER
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#endif
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// the parser stores a node's first word at once where the layout of `node` is
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// known to be little-endian (MSVC targets are); elsewhere field by field
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#if (defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__) || defined(_MSC_VER)
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#define NLOHMANN_VIEW_LITTLE_ENDIAN 1
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#else
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#define NLOHMANN_VIEW_LITTLE_ENDIAN 0
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#endif
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/// eight checks at fixed offsets 0..7
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#define NLOHMANN_VIEW_REPEAT_FIRST_8(X) X(0) X(1) X(2) X(3) X(4) X(5) X(6) X(7)
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/// eight checks at fixed offsets 8..15
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#define NLOHMANN_VIEW_REPEAT_SECOND_8(X) X(8) X(9) X(10) X(11) X(12) X(13) X(14) X(15)
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/// sixteen checks at fixed offsets 0..15
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#define NLOHMANN_VIEW_REPEAT16(X) NLOHMANN_VIEW_REPEAT_FIRST_8(X) NLOHMANN_VIEW_REPEAT_SECOND_8(X)
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