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d6aaa23a2b
Allow defining variables and perform cast with a typeof which removes the volatile and const qualifiers. This prevents declaring a stack variable with a volatile qualifier within a macro, which would generate sub-optimal assembler. This is imported from the "librseq" project. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
63 lines
1.8 KiB
C++
63 lines
1.8 KiB
C++
/* SPDX-License-Identifier: LGPL-2.1-only OR MIT */
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/*
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* rseq/compiler.h
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*
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* Work-around asm goto compiler bugs.
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*
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* (C) Copyright 2021 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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*/
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#ifndef RSEQ_COMPILER_H
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#define RSEQ_COMPILER_H
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/*
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* gcc prior to 4.8.2 miscompiles asm goto.
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* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
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*
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* gcc prior to 8.1.0 miscompiles asm goto at O1.
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* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103908
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*
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* clang prior to version 13.0.1 miscompiles asm goto at O2.
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* https://github.com/llvm/llvm-project/issues/52735
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*
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* Work around these issues by adding a volatile inline asm with
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* memory clobber in the fallthrough after the asm goto and at each
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* label target. Emit this for all compilers in case other similar
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* issues are found in the future.
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*/
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#define rseq_after_asm_goto() asm volatile ("" : : : "memory")
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/* Combine two tokens. */
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#define RSEQ__COMBINE_TOKENS(_tokena, _tokenb) \
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_tokena##_tokenb
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#define RSEQ_COMBINE_TOKENS(_tokena, _tokenb) \
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RSEQ__COMBINE_TOKENS(_tokena, _tokenb)
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#ifdef __cplusplus
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#define rseq_unqual_scalar_typeof(x) \
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std::remove_cv<std::remove_reference<decltype(x)>::type>::type
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#else
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#define rseq_scalar_type_to_expr(type) \
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unsigned type: (unsigned type)0, \
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signed type: (signed type)0
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/*
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* Use C11 _Generic to express unqualified type from expression. This removes
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* volatile qualifier from expression type.
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*/
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#define rseq_unqual_scalar_typeof(x) \
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__typeof__( \
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_Generic((x), \
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char: (char)0, \
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rseq_scalar_type_to_expr(char), \
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rseq_scalar_type_to_expr(short), \
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rseq_scalar_type_to_expr(int), \
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rseq_scalar_type_to_expr(long), \
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rseq_scalar_type_to_expr(long long), \
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default: (x) \
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) \
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)
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#endif
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#endif /* RSEQ_COMPILER_H_ */
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