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 #endif  /* RSEQ_COMPILER_H_ */
37