251 lines
8.8 KiB
C
251 lines
8.8 KiB
C
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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_COMPILER_SPECIFIC_H_
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#define BASE_COMPILER_SPECIFIC_H_
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#include "build/build_config.h"
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#if defined(COMPILER_MSVC) && !defined(__clang__)
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#error "Only clang-cl is supported on Windows, see https://crbug.com/988071"
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#endif
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// Annotate a variable indicating it's ok if the variable is not used.
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// (Typically used to silence a compiler warning when the assignment
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// is important for some other reason.)
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// Use like:
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// int x = ...;
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// ALLOW_UNUSED_LOCAL(x);
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#define ALLOW_UNUSED_LOCAL(x) (void)x
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// Annotate a typedef or function indicating it's ok if it's not used.
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// Use like:
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// typedef Foo Bar ALLOW_UNUSED_TYPE;
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#if defined(COMPILER_GCC) || defined(__clang__)
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#define ALLOW_UNUSED_TYPE __attribute__((unused))
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#else
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#define ALLOW_UNUSED_TYPE
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#endif
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// Annotate a function indicating it should not be inlined.
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// Use like:
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// NOINLINE void DoStuff() { ... }
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#if defined(COMPILER_GCC)
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#define NOINLINE __attribute__((noinline))
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#elif defined(COMPILER_MSVC)
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#define NOINLINE __declspec(noinline)
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#else
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#define NOINLINE
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#endif
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#if defined(COMPILER_GCC) && defined(NDEBUG)
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#define ALWAYS_INLINE inline __attribute__((__always_inline__))
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#elif defined(COMPILER_MSVC) && defined(NDEBUG)
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#define ALWAYS_INLINE __forceinline
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#else
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#define ALWAYS_INLINE inline
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#endif
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// Specify memory alignment for structs, classes, etc.
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// Use like:
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// class ALIGNAS(16) MyClass { ... }
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// ALIGNAS(16) int array[4];
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//
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// In most places you can use the C++11 keyword "alignas", which is preferred.
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//
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// But compilers have trouble mixing __attribute__((...)) syntax with
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// alignas(...) syntax.
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//
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// Doesn't work in clang or gcc:
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// struct alignas(16) __attribute__((packed)) S { char c; };
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// Works in clang but not gcc:
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// struct __attribute__((packed)) alignas(16) S2 { char c; };
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// Works in clang and gcc:
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// struct alignas(16) S3 { char c; } __attribute__((packed));
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//
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// There are also some attributes that must be specified *before* a class
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// definition: visibility (used for exporting functions/classes) is one of
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// these attributes. This means that it is not possible to use alignas() with a
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// class that is marked as exported.
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#if defined(COMPILER_MSVC)
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#define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
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#elif defined(COMPILER_GCC)
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#define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
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#endif
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// Annotate a function indicating the caller must examine the return value.
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// Use like:
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// int foo() WARN_UNUSED_RESULT;
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// To explicitly ignore a result, see |ignore_result()| in base/macros.h.
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#undef WARN_UNUSED_RESULT
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#if defined(COMPILER_GCC) || defined(__clang__)
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#define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
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#else
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#define WARN_UNUSED_RESULT
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#endif
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// Tell the compiler a function is using a printf-style format string.
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// |format_param| is the one-based index of the format string parameter;
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// |dots_param| is the one-based index of the "..." parameter.
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// For v*printf functions (which take a va_list), pass 0 for dots_param.
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// (This is undocumented but matches what the system C headers do.)
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// For member functions, the implicit this parameter counts as index 1.
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#if defined(COMPILER_GCC) || defined(__clang__)
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#define PRINTF_FORMAT(format_param, dots_param) \
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__attribute__((format(printf, format_param, dots_param)))
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#else
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#define PRINTF_FORMAT(format_param, dots_param)
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#endif
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// WPRINTF_FORMAT is the same, but for wide format strings.
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// This doesn't appear to yet be implemented in any compiler.
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// See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38308 .
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#define WPRINTF_FORMAT(format_param, dots_param)
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// If available, it would look like:
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// __attribute__((format(wprintf, format_param, dots_param)))
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// Sanitizers annotations.
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#if defined(__has_attribute)
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#if __has_attribute(no_sanitize)
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#define NO_SANITIZE(what) __attribute__((no_sanitize(what)))
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#endif
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#endif
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#if !defined(NO_SANITIZE)
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#define NO_SANITIZE(what)
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#endif
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// MemorySanitizer annotations.
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#if defined(MEMORY_SANITIZER) && !defined(OS_NACL)
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#include <sanitizer/msan_interface.h>
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// Mark a memory region fully initialized.
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// Use this to annotate code that deliberately reads uninitialized data, for
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// example a GC scavenging root set pointers from the stack.
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#define MSAN_UNPOISON(p, size) __msan_unpoison(p, size)
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// Check a memory region for initializedness, as if it was being used here.
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// If any bits are uninitialized, crash with an MSan report.
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// Use this to sanitize data which MSan won't be able to track, e.g. before
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// passing data to another process via shared memory.
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#define MSAN_CHECK_MEM_IS_INITIALIZED(p, size) \
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__msan_check_mem_is_initialized(p, size)
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#else // MEMORY_SANITIZER
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#define MSAN_UNPOISON(p, size)
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#define MSAN_CHECK_MEM_IS_INITIALIZED(p, size)
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#endif // MEMORY_SANITIZER
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// DISABLE_CFI_PERF -- Disable Control Flow Integrity for perf reasons.
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#if !defined(DISABLE_CFI_PERF)
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#if defined(__clang__) && defined(OFFICIAL_BUILD)
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#define DISABLE_CFI_PERF __attribute__((no_sanitize("cfi")))
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#else
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#define DISABLE_CFI_PERF
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#endif
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#endif
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// Macro useful for writing cross-platform function pointers.
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#if !defined(CDECL)
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#if defined(OS_WIN)
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#define CDECL __cdecl
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#else // defined(OS_WIN)
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#define CDECL
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#endif // defined(OS_WIN)
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#endif // !defined(CDECL)
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// Macro for hinting that an expression is likely to be false.
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#if !defined(UNLIKELY)
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#if defined(COMPILER_GCC) || defined(__clang__)
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#define UNLIKELY(x) __builtin_expect(!!(x), 0)
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#else
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#define UNLIKELY(x) (x)
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#endif // defined(COMPILER_GCC)
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#endif // !defined(UNLIKELY)
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#if !defined(LIKELY)
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#if defined(COMPILER_GCC) || defined(__clang__)
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#define LIKELY(x) __builtin_expect(!!(x), 1)
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#else
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#define LIKELY(x) (x)
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#endif // defined(COMPILER_GCC)
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#endif // !defined(LIKELY)
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// Compiler feature-detection.
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// clang.llvm.org/docs/LanguageExtensions.html#has-feature-and-has-extension
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#if defined(__has_feature)
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#define HAS_FEATURE(FEATURE) __has_feature(FEATURE)
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#else
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#define HAS_FEATURE(FEATURE) 0
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#endif
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// Macro for telling -Wimplicit-fallthrough that a fallthrough is intentional.
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#if defined(__clang__)
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#define FALLTHROUGH [[clang::fallthrough]]
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#else
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#define FALLTHROUGH
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#endif
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#if defined(COMPILER_GCC)
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#define PRETTY_FUNCTION __PRETTY_FUNCTION__
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#elif defined(COMPILER_MSVC)
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#define PRETTY_FUNCTION __FUNCSIG__
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#else
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// See https://en.cppreference.com/w/c/language/function_definition#func
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#define PRETTY_FUNCTION __func__
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#endif
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#if !defined(CPU_ARM_NEON)
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#if defined(__arm__)
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#if !defined(__ARMEB__) && !defined(__ARM_EABI__) && !defined(__EABI__) && \
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!defined(__VFP_FP__) && !defined(_WIN32_WCE) && !defined(ANDROID)
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#error Chromium does not support middle endian architecture
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#endif
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#if defined(__ARM_NEON__)
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#define CPU_ARM_NEON 1
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#endif
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#endif // defined(__arm__)
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#endif // !defined(CPU_ARM_NEON)
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#if !defined(HAVE_MIPS_MSA_INTRINSICS)
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#if defined(__mips_msa) && defined(__mips_isa_rev) && (__mips_isa_rev >= 5)
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#define HAVE_MIPS_MSA_INTRINSICS 1
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#endif
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#endif
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#if defined(__clang__) && __has_attribute(uninitialized)
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// Attribute "uninitialized" disables -ftrivial-auto-var-init=pattern for
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// the specified variable.
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// Library-wide alternative is
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// 'configs -= [ "//build/config/compiler:default_init_stack_vars" ]' in .gn
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// file.
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//
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// See "init_stack_vars" in build/config/compiler/BUILD.gn and
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// http://crbug.com/977230
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// "init_stack_vars" is enabled for non-official builds and we hope to enable it
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// in official build in 2020 as well. The flag writes fixed pattern into
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// uninitialized parts of all local variables. In rare cases such initialization
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// is undesirable and attribute can be used:
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// 1. Degraded performance
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// In most cases compiler is able to remove additional stores. E.g. if memory is
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// never accessed or properly initialized later. Preserved stores mostly will
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// not affect program performance. However if compiler failed on some
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// performance critical code we can get a visible regression in a benchmark.
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// 2. memset, memcpy calls
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// Compiler may replaces some memory writes with memset or memcpy calls. This is
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// not -ftrivial-auto-var-init specific, but it can happen more likely with the
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// flag. It can be a problem if code is not linked with C run-time library.
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//
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// Note: The flag is security risk mitigation feature. So in future the
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// attribute uses should be avoided when possible. However to enable this
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// mitigation on the most of the code we need to be less strict now and minimize
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// number of exceptions later. So if in doubt feel free to use attribute, but
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// please document the problem for someone who is going to cleanup it later.
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// E.g. platform, bot, benchmark or test name in patch description or next to
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// the attribute.
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#define STACK_UNINITIALIZED __attribute__((uninitialized))
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#else
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#define STACK_UNINITIALIZED
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#endif
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#endif // BASE_COMPILER_SPECIFIC_H_
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