tools/testing/selftests/rseq/compiler.h

   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 <[email protected]>
   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_ */