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debug: add variable escape and memory clobber functions

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This commit is contained in:
Danny Robson 2017-08-18 11:15:00 +10:00
parent c49738e7a3
commit 46d28ba7be
1 changed files with 66 additions and 0 deletions
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66
debug.hpp
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@ -221,6 +221,7 @@
#define CHECK_NEZ(A) do { \
DEBUG_ONLY ( \
const auto &__a = (A); \
\
if (::util::exactly_zero (__a)) \
_CHECK_PANIC ("expected non-zero\n" \
"__a: %s is %!", \
@ -234,6 +235,7 @@
DEBUG_ONLY ( \
const auto &__check_mod_v = (V); \
const auto &__check_mod_m = (M); \
\
if (!::util::exactly_zero (__check_mod_v % __check_mod_m)) \
_CHECK_PANIC ("expected zero modulus\n" \
"__v: %s is %!\n" \
@ -296,6 +298,70 @@
} while (0)
///////////////////////////////////////////////////////////////////////////////
/// make the compiler think a particular variable may now be aliased somewhere.
///
/// useful for preventing optimisations eliding a variable.
///
/// stolen from Chandler Carruth's 2015 talk: "Tuning C++".
namespace util::debug {
template <class T>
inline T*
escape (T *t)
{
asm volatile ("": : "g"(t): "memory");
return t;
}
template <class T>
inline const T*
escape (const T *t)
{
asm volatile ("": : "g"(t): "memory");
return t;
}
template <class T>
inline const T&
escape (const T &t)
{
return *escape (&t);
}
template <class T>
inline T&
escape (T &t)
{
return *escape (&t);
}
template <typename T, typename ...Args>
inline void
escape (T t, Args ...args)
{
escape (t);
escape (args...);
}
}
///////////////////////////////////////////////////////////////////////////////
/// force the compiler to conceptually dirty the global memory space.
///
/// stolen from Chandler Carruth's 2015 talk: "Tuning C++".
namespace util::debug {
inline void
clobber (void)
{
asm volatile ("": : : "memory");
}
}
///////////////////////////////////////////////////////////////////////////////
constexpr void panic [[noreturn]] (const char*);