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Add etl::is_constant_evaluated (#1198)

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Co-authored-by: John Wellbelove <jwellbelove@users.noreply.github.com>
This commit is contained in:
Roland Reichwein 2025-10-08 10:32:43 +02:00 committed by GitHub
parent 85fc48302d
commit 05731c2786
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3 changed files with 53 additions and 0 deletions
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13
include/etl/profiles/determine_builtin_support.h
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@ -55,6 +55,10 @@ SOFTWARE.
#if !defined(ETL_USING_BUILTIN_UNDERLYING_TYPE)
#define ETL_USING_BUILTIN_UNDERLYING_TYPE 1
#endif
#if !defined(ETL_USING_BUILTIN_IS_CONSTANT_EVALUATED)
#define ETL_USING_BUILTIN_IS_CONSTANT_EVALUATED 1
#endif
#endif
#if defined(__has_builtin) && !defined(ETL_COMPILER_MICROSOFT) // Use __has_builtin to check for existence of builtin functions? Fix VS2022 intellisense issue.
@ -82,6 +86,10 @@ SOFTWARE.
#define ETL_USING_BUILTIN_UNDERLYING_TYPE __has_builtin(__underlying_type)
#endif
#if !defined(ETL_USING_BUILTIN_IS_CONSTANT_EVALUATED)
#define ETL_USING_BUILTIN_IS_CONSTANT_EVALUATED __has_builtin(__builtin_is_constant_evaluated)
#endif
#if !defined(ETL_USING_BUILTIN_MEMCPY)
#define ETL_USING_BUILTIN_MEMCPY __has_builtin(__builtin_memcpy)
#endif
@ -128,6 +136,10 @@ SOFTWARE.
#define ETL_USING_BUILTIN_UNDERLYING_TYPE 0
#endif
#if !defined(ETL_USING_BUILTIN_IS_CONSTANT_EVALUATED)
#define ETL_USING_BUILTIN_IS_CONSTANT_EVALUATED 0
#endif
#if !defined(ETL_USING_BUILTIN_MEMCPY)
#define ETL_USING_BUILTIN_MEMCPY 0
#endif
@ -160,6 +172,7 @@ namespace etl
static ETL_CONSTANT bool using_builtin_is_trivially_destructible = (ETL_USING_BUILTIN_IS_TRIVIALLY_DESTRUCTIBLE == 1);
static ETL_CONSTANT bool using_builtin_is_trivially_copyable = (ETL_USING_BUILTIN_IS_TRIVIALLY_COPYABLE == 1);
static ETL_CONSTANT bool using_builtin_underlying_type = (ETL_USING_BUILTIN_UNDERLYING_TYPE == 1);
static ETL_CONSTANT bool using_builtin_is_constant_evaluated = (ETL_USING_BUILTIN_IS_CONSTANT_EVALUATED == 1);
static ETL_CONSTANT bool using_builtin_memcpy = (ETL_USING_BUILTIN_MEMCPY == 1);
static ETL_CONSTANT bool using_builtin_memmove = (ETL_USING_BUILTIN_MEMMOVE == 1);
static ETL_CONSTANT bool using_builtin_memset = (ETL_USING_BUILTIN_MEMSET == 1);

22
include/etl/type_traits.h
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@ -2482,6 +2482,28 @@ typedef integral_constant<bool, true> true_type;
template <typename T, template <typename...> class Template>
inline constexpr bool is_specialization_v = etl::is_specialization<T, Template>::value;
#endif
//*********************************************
// is_constant_evaluated
ETL_CONSTEXPR inline bool is_constant_evaluated() ETL_NOEXCEPT
{
#if ETL_USING_CPP23
if consteval
{
return true;
}
else
{
return false;
}
#elif ETL_USING_BUILTIN_IS_CONSTANT_EVALUATED == 1
// fallback for C++20 on supported compilers
return __builtin_is_constant_evaluated();
#else
// default if unsupported
return false;
#endif
}
}
// Helper macros

18
test/test_type_traits.cpp
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@ -1472,4 +1472,22 @@ namespace
CHECK_FALSE((etl::is_specialization<other_specialized<int>, specialized>::value));
#endif
}
#if ETL_USING_CPP11
//*************************************************************************
TEST(test_is_constant_evaluated)
{
const bool c0 = etl::is_constant_evaluated();
#if !ETL_USING_CPP23 && defined(ETL_COMPILER_MICROSOFT)
// Not supported on MSVC via __has_builtin, see determine_builtin_support.h
CHECK_FALSE(c0);
#else
CHECK_TRUE(c0);
#endif
volatile int i = 1;
const bool c1 = (((i == 1) && etl::is_constant_evaluated()) ? true : false);
CHECK_FALSE(c1);
}
#endif
}