include/rseq/compiler.h

   1 /* SPDX-License-Identifier: MIT */
   2 /* SPDX-FileCopyrightText: 2021 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> */
   3
   4 /*
   5  * rseq/compiler.h
   6  *
   7  * Work-around asm goto compiler bugs.
   8  */
   9
  10 #ifndef RSEQ_COMPILER_H
  11 #define RSEQ_COMPILER_H
  12
  13 #if defined __cplusplus
  14 # include <type_traits> /* for std::remove_cv */
  15 #endif
  16
  17 /*
  18  * gcc prior to 4.8.2 miscompiles asm goto.
  19  * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
  20  *
  21  * gcc prior to 8.1.0 miscompiles asm goto at O1.
  22  * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103908
  23  *
  24  * clang prior to version 13.0.1 miscompiles asm goto at O2.
  25  * https://github.com/llvm/llvm-project/issues/52735
  26  *
  27  * Work around these issues by adding a volatile inline asm with
  28  * memory clobber in the fallthrough after the asm goto and at each
  29  * label target.  Emit this for all compilers in case other similar
  30  * issues are found in the future.
  31  */
  32 #define rseq_after_asm_goto()   __asm__ __volatile__ ("" : : : "memory")
  33
  34 /* Combine two tokens. */
  35 #define RSEQ__COMBINE_TOKENS(_tokena, _tokenb)  \
  36         _tokena##_tokenb
  37 #define RSEQ_COMBINE_TOKENS(_tokena, _tokenb)   \
  38         RSEQ__COMBINE_TOKENS(_tokena, _tokenb)
  39
  40 #if defined(__SIZEOF_LONG__)
  41 #define RSEQ_BITS_PER_LONG      (__SIZEOF_LONG__ * 8)
  42 #elif defined(_LP64)
  43 #define RSEQ_BITS_PER_LONG      64
  44 #else
  45 #define RSEQ_BITS_PER_LONG      32
  46 #endif
  47
  48 #ifdef __cplusplus
  49 #define rseq_unqual_scalar_typeof(x)                                    \
  50         std::remove_cv<std::remove_reference<decltype(x)>::type>::type
  51 #else
  52 #define rseq_scalar_type_to_expr(type)                                  \
  53         unsigned type: (unsigned type)0,                                \
  54         signed type: (signed type)0
  55
  56 /*
  57  * Use C11 _Generic to express unqualified type from expression. This removes
  58  * volatile qualifier from expression type.
  59  */
  60 #define rseq_unqual_scalar_typeof(x)                                    \
  61         __typeof__(                                                     \
  62                 _Generic((x),                                           \
  63                         char: (char)0,                                  \
  64                         rseq_scalar_type_to_expr(char),                 \
  65                         rseq_scalar_type_to_expr(short),                \
  66                         rseq_scalar_type_to_expr(int),                  \
  67                         rseq_scalar_type_to_expr(long),                 \
  68                         rseq_scalar_type_to_expr(long long),            \
  69                         default: (x)                                    \
  70                 )                                                       \
  71         )
  72 #endif
  73
  74 #endif  /* RSEQ_COMPILER_H_ */