1/* SPDX-License-Identifier: LGPL-2.1-only OR MIT */
 2/*
 3 * rseq/compiler.h
 4 *
 5 * Work-around asm goto compiler bugs.
 6 *
 7 * (C) Copyright 2021 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 8 */
 9
10#ifndef RSEQ_COMPILER_H
11#define RSEQ_COMPILER_H
12
13/*
14 * gcc prior to 4.8.2 miscompiles asm goto.
15 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
16 *
17 * gcc prior to 8.1.0 miscompiles asm goto at O1.
18 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103908
19 *
20 * clang prior to version 13.0.1 miscompiles asm goto at O2.
21 * https://github.com/llvm/llvm-project/issues/52735
22 *
23 * Work around these issues by adding a volatile inline asm with
24 * memory clobber in the fallthrough after the asm goto and at each
25 * label target.  Emit this for all compilers in case other similar
26 * issues are found in the future.
27 */
28#define rseq_after_asm_goto()	asm volatile ("" : : : "memory")
29
30/* Combine two tokens. */
31#define RSEQ__COMBINE_TOKENS(_tokena, _tokenb)	\
32	_tokena##_tokenb
33#define RSEQ_COMBINE_TOKENS(_tokena, _tokenb)	\
34	RSEQ__COMBINE_TOKENS(_tokena, _tokenb)
35
36#ifdef __cplusplus
37#define rseq_unqual_scalar_typeof(x)					\
38	std::remove_cv<std::remove_reference<decltype(x)>::type>::type
39#else
40#define rseq_scalar_type_to_expr(type)					\
41	unsigned type: (unsigned type)0,				\
42	signed type: (signed type)0
43
44/*
45 * Use C11 _Generic to express unqualified type from expression. This removes
46 * volatile qualifier from expression type.
47 */
48#define rseq_unqual_scalar_typeof(x)					\
49	__typeof__(							\
50		_Generic((x),						\
51			char: (char)0,					\
52			rseq_scalar_type_to_expr(char),			\
53			rseq_scalar_type_to_expr(short),		\
54			rseq_scalar_type_to_expr(int),			\
55			rseq_scalar_type_to_expr(long),			\
56			rseq_scalar_type_to_expr(long long),		\
57			default: (x)					\
58		)							\
59	)
60#endif
61
62#endif  /* RSEQ_COMPILER_H_ */