104 lines
3.7 KiB
C
104 lines
3.7 KiB
C
// Copyright 2017 The Dawn Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef SRC_DAWN_COMMON_COMPILER_H_
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#define SRC_DAWN_COMMON_COMPILER_H_
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// Defines macros for compiler-specific functionality
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// - DAWN_COMPILER_IS(CLANG|GCC|MSVC): Compiler detection
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// - DAWN_BUILTIN_UNREACHABLE(): Hints the compiler that a code path is unreachable
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// - DAWN_(UN)?LIKELY(EXPR): Where available, hints the compiler that the expression will be true
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// (resp. false) to help it generate code that leads to better branch prediction.
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// - DAWN_UNUSED(EXPR): Prevents unused variable/expression warnings on EXPR.
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// - DAWN_UNUSED_FUNC(FUNC): Prevents unused function warnings on FUNC.
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// - DAWN_DECLARE_UNUSED: Prevents unused function warnings a subsequent declaration.
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// Both DAWN_UNUSED_FUNC and DAWN_DECLARE_UNUSED may be necessary, e.g. to suppress clang's
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// unneeded-internal-declaration warning.
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// Clang and GCC, check for __clang__ too to catch clang-cl masquarading as MSVC
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#if defined(__GNUC__) || defined(__clang__)
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#if defined(__clang__)
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#define DAWN_COMPILER_IS_CLANG 1
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#else
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#define DAWN_COMPILER_IS_GCC 1
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#endif
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#define DAWN_BUILTIN_UNREACHABLE() __builtin_unreachable()
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#define DAWN_LIKELY(x) __builtin_expect(!!(x), 1)
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#define DAWN_UNLIKELY(x) __builtin_expect(!!(x), 0)
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#if !defined(__has_cpp_attribute)
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#define __has_cpp_attribute(name) 0
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#endif
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#define DAWN_DECLARE_UNUSED __attribute__((unused))
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#if defined(NDEBUG)
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#define DAWN_FORCE_INLINE inline __attribute__((always_inline))
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#endif
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#define DAWN_NOINLINE __attribute__((noinline))
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// MSVC
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#elif defined(_MSC_VER)
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#define DAWN_COMPILER_IS_MSVC 1
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#define DAWN_BUILTIN_UNREACHABLE() __assume(false)
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#define DAWN_DECLARE_UNUSED
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#if defined(NDEBUG)
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#define DAWN_FORCE_INLINE __forceinline
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#endif
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#define DAWN_NOINLINE __declspec(noinline)
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#else
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#error "Unsupported compiler"
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#endif
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// This section defines other compiler macros to 0 to avoid undefined macro usage error.
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#if !defined(DAWN_COMPILER_IS_CLANG)
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#define DAWN_COMPILER_IS_CLANG 0
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#endif
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#if !defined(DAWN_COMPILER_IS_GCC)
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#define DAWN_COMPILER_IS_GCC 0
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#endif
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#if !defined(DAWN_COMPILER_IS_MSVC)
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#define DAWN_COMPILER_IS_MSVC 0
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#endif
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// Use #if DAWN_COMPILER_IS(XXX) for compiler specific code.
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// Do not use #ifdef or the naked macro DAWN_COMPILER_IS_XXX.
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// This can help avoid common mistakes like not including "Compiler.h" and falling into unwanted
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// code block as usage of undefined macro "function" will be blocked by the compiler.
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#define DAWN_COMPILER_IS(X) (1 == DAWN_COMPILER_IS_##X)
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// It seems that (void) EXPR works on all compilers to silence the unused variable warning.
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#define DAWN_UNUSED(EXPR) (void)EXPR
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// Likewise using static asserting on sizeof(&FUNC) seems to make it tagged as used
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#define DAWN_UNUSED_FUNC(FUNC) static_assert(sizeof(&FUNC) == sizeof(void (*)()))
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// Add noop replacements for macros for features that aren't supported by the compiler.
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#if !defined(DAWN_LIKELY)
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#define DAWN_LIKELY(X) X
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#endif
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#if !defined(DAWN_UNLIKELY)
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#define DAWN_UNLIKELY(X) X
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#endif
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#if !defined(DAWN_FORCE_INLINE)
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#define DAWN_FORCE_INLINE inline
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#endif
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#if !defined(DAWN_NOINLINE)
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#define DAWN_NOINLINE
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#endif
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#endif // SRC_DAWN_COMMON_COMPILER_H_
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