Enabling compiler built-ins

20.24.0

Many of the features or options in the ETL can be enhanced by the use of compiler built-ins.

If built-ins are available and the STL is not used, then many copy type algorithms may be declared as constexpr.

Also, some type traits can detect types more correctly.

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Controlling Macros

If any of these are set to 1, then the ETL will use the compiler built-ins, were applicable.

Setting them to 0 will disable the use of the built-in.

Setting any of these in the project or etl_profile.h will override any later tests.

ETL_USE_BUILTIN_MEMCPY

ETL_USE_BUILTIN_MEMCMP

ETL_USE_BUILTIN_MEMMOVE

ETL_USE_BUILTIN_MEMSET

ETL_USE_BUILTIN_IS_ASSIGNABLE

ETL_USE_BUILTIN_IS_CONSTRUCTIBLE

ETL_USE_BUILTIN_IS_TRIVIALLY_CONSTRUCTIBLE

ETL_USE_BUILTIN_IS_TRIVIALLY_DESTRUCTIBLE

ETL_USE_BUILTIN_IS_TRIVIALLY_COPYABLE

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Defining macros

The use of built-ins can be controlled by macros.

If ETL_USING_MEM_BUILTINS is defined and the corresponding macro has not already been set, then following

will be set to 1.

ETL_USE_BUILTIN_MEMCPY

ETL_USE_BUILTIN_MEMCMP

ETL_USE_BUILTIN_MEMMOVE

ETL_USE_BUILTIN_MEMSET

If ETL_USING_TYPE_TRAITS_BUILTINS is defined and the corresponding macro has not already been set, then following

will be set to 1.

ETL_USE_BUILTIN_IS_ASSIGNABLE

ETL_USE_BUILTIN_IS_CONSTRUCTIBLE

ETL_USE_BUILTIN_IS_TRIVIALLY_CONSTRUCTIBLE

ETL_USE_BUILTIN_IS_TRIVIALLY_DESTRUCTIBLE

ETL_USE_BUILTIN_IS_TRIVIALLY_COPYABLE

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Detection of built-ins

These tests occur after the above macro tests.

The ETL will attempt to check the availability of compiler built-ins.

If __has_builtin exists, then the existence of the following built-ins are checked.

If not already defined, the corresponding macro is set according to the result.

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Sets ETL_USE_BUILTIN_MEMCPY = 1 if __builtin_memcmp exists, otherwise 0.

Sets ETL_USE_BUILTIN_MEMCPY = 1 if __builtin_memcpy exists, otherwise 0.

Sets ETL_USE_BUILTIN_MEMMOVE = 1 if __builtin_memmove exists, otherwise 0.

Sets ETL_USE_BUILTIN_MEMSET = 1 if __builtin_memset exists, otherwise 0.

Sets ETL_USE_BUILTIN_IS_ASSIGNABLE = 1 if __is_assignable exists, otherwise 0.

Sets ETL_USE_BUILTIN_IS_CONSTRUCTIBLE = 1 if __is_constructible exists, otherwise 0.

Sets ETL_USE_BUILTIN_IS_TRIVIALLY_CONSTRUCTIBLE = 1 if __has_trivial_constructor or

__is_trivially_constructible exists, otherwise 0.

Sets ETL_USE_BUILTIN_IS_TRIVIALLY_DESTRUCTIBLE = 1 if __has_trivial_destructor

or __is_trivially_destructible exists, otherwise 0.

Sets ETL_USE_BUILTIN_IS_TRIVIALLY_COPYABLE = 1 if __has_trivial_copy

or __is_trivially_copyable exists, otherwise 0.

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Default

Finally, any macro that has so far not been defined will be defined as 0.